The History of 60Hz A.C. ?
Griff Hopkins
Can anyone enlighten me on the history of 60Hz as the (U.S.)
standard line frequency. I seem to remember being taught that
60Hz came about as a result of electric clocks (i.e.- the clocks
needed 60 cycles). While this makes sense (to ignorant me), it
certainly doesn't explain the use of 50Hz standards used by other
countries!?!?
It would appear that 60Hz isn't the most efficient frequency at
which to transfer power. Aviation electronics has been using
400Hz for as long as I remember. At 400Hz, transformers and power
supply filters are significantly smaller. Also, EMF (low freq.
health) problems would seem to be greatly dimenished.
I would appreciate any enlightenment on the history, use, and
possible future trends for A.C. Power transfer. Thank you for
your time.
Griff Hopkins
Director of Engineering/
Primus Technology Group
Charles L. Perrin
Griff Hopkins <75561...@CompuServe.COM> wrote:
>Can anyone enlighten me on the history of 60Hz as the (U.S.)
>standard line frequency.
>It would appear that 60Hz isn't the most efficient frequency at
>which to transfer power. Aviation electronics has been using
>400Hz for as long as I remember. At 400Hz, transformers and power
>supply filters are significantly smaller. Also, EMF (low freq.
>health) problems would seem to be greatly dimenished.
It's a tradeoff between capacitive/inductive transmission losses
(which are higher at higher frequencies) and the sizes of the
transformers/filters.
Also, if you get much below 50Hz, light bulbs tend to turn into strobe
lights.
--------------------------------------------------------------
Charlie's Sneaker Pages: http://sneakers.pair.com/
Best Value in Airplanes: http://www.boeing.com/
--------------------------------------------------------------
Anthony Morton
[I've added soc.history.science to the newsgroups list, as people there may
have something to contribute. sci.electronics and sci.physics groups will be
removed from followups as this issue probably isn't particularly relevant to
them - TM]
In article <4s97l3$r6s$1...@mhadg.production.compuserve.com>,
Griff Hopkins <75561...@CompuServe.COM> wrote:
>Can anyone enlighten me on the history of 60Hz as the (U.S.)
>standard line frequency. I seem to remember being taught that
>60Hz came about as a result of electric clocks (i.e.- the clocks
>needed 60 cycles). While this makes sense (to ignorant me), it
>certainly doesn't explain the use of 50Hz standards used by other
>countries!?!?
In the early days of electricity, before anyone gave any thought to
standardisation, there was a proliferation of systems: DC and AC, widely
varying voltages, and (in the case of AC) widely varying frequencies.
When the first AC systems were developed, lighting was still by far the
principal application, and so the choice of frequency was fairly arbitrary,
though one tended to avoid very low frequencies as this caused lights to
flicker undesirably. The maximum frequency I believe was constrained more by
the design of the early AC machines than by a desire to minimise transmission
losses, as in those days transmission losses were dwarfed by losses in the
fairly primitive transformers of the day. Electric clocks didn't appear on
the scene until much later, when frequencies had already been standardised.
I've done a bit of research into the history of electricity in my own state
of Victoria, Australia. It seems that when Melbourne City Council (supplier
of electricity within the Melbourne CBD until 1994) installed its first AC
plant in 1894 it didn't even bother specifying the frequency, which turned out
to be 72Hz! The 72Hz consumers were later changed over to DC, and then to a
50Hz system. It is worth noting that DC continued to be used in the Melbourne
CBD for most of this century, with the maximum DC load occuring in 1930.
Victoria's electric railways initially used 25Hz AC, but were subsequently
changed over to DC (supplied by rectifiers from three-phase AC feeders).
Our State Electricity Commission, formed shortly after the First World War,
played a major role in standardising the state's electricity to 50Hz AC. By
WWII, the only nonstandard load in Victoria was the DC in Melbourne noted
above. Similar state-owned utilities in other states of Australia achieved a
similar standardisation, though some remote areas with independent supplies
continued to use different frequencies (Broken Hill ran on 40Hz until
comparatively recent times, so I'm told). A key advantage of standardisation
was that the same appliances could be used in any location (including electric
clocks, of course).
The 60Hz used in America originated, I believe, with the Westinghouse Company
and the Niagara Falls project in the 1890s. Regarding the existence of two
separate standards, one in the US and another elsewhere, I can only say that
it's not the first or only occurrence of this phenomenon (English spelling,
weights and measures, and toilets spring to mind immediately). I believe
there are some Asian countries that also use 60Hz AC, though I couldn't say
which they are. If I recall correctly, a previous thread in one of these
newsgroups mentioned that Japan has or had two separate systems, one running
on 50Hz and the other on 60Hz!
Hope you find some of this useful....
--
Tony Morton
University of Melbourne
John Atwood
Griff Hopkins <75561...@CompuServe.COM> writes:
>Can anyone enlighten me on the history of 60Hz as the (U.S.)
>standard line frequency.
The power line frequency came about as a result of what worked best with
large AC motors, as well as what was economical to transmit over power
lines. In the early days of AC power distribution (about 100 years ago),
several different frequencies were used in North America: 25, 40, 50, and
60 Hz, among others. 25 Hz was especially useful for large industrial
installations. The choice of frequency related to the rpm of large
multi-pole motors. By the 1920s, 60 Hz was becoming dominant in North
America, while 50 Hz was dominant in Europe. By the late 1930s, virtually all
power companies in North America had changed to 60 Hz. However, many industrial
plants were still set up for 25 Hz, so the local power companies would often
set-up large motor-generators to change 60 Hz to 25 Hz for these sites.
I remember when I was a kid (perhaps around 1959) visiting New York City
and noticing that the incandescent lights in an older subway station were
noticeably flickering. My dad said that the subway power was running on 25 Hz.
I later read articles about how Consolidated Edison in N.Y. ran big motor-
generators to supply the 25 Hz subway system power, as well as running motor-
generators to supply DC power to the islands of DC power in downtown N.Y.
City.
>It would appear that 60Hz isn't the most efficient frequency at
>which to transfer power. Aviation electronics has been using
>400Hz for as long as I remember. At 400Hz, transformers and power
>supply filters are significantly smaller. Also, EMF (low freq.
>health) problems would seem to be greatly dimenished.
400Hz is good for aircraft or similarly small environments, but for wide-
spread distribution, the AC losses would be excessive. Even at 60 Hz, one
thousand-mile transmission lines are difficult to keep synchronized! The
problem with lower frequencies, such as 25 Hz (other than light flickering)
is the larger amount of iron needed in transformers and motors. Above 60 Hz,
more care has to be taken to avoid eddy-current losses. On an airplane, where
weight is a big factor, the cost of magnetics for high frquencies is less
of an issue.
With the advent of cheap, smart switching technologies (MOSFETS, IGBTs, etc.)
distribution by DC is starting to look attractive. DC is already used for
big point-to-point power distribution (such as the Pacific Intertie between
Washington state and Los Angeles). Perhaps as semiconductor technology
improves, DC distribution may become cost-effective for local power
distribution.
- John Atwood
--
John Atwood
Preferred e-mail address: atw...@one-electron.com
William E. Sabin
Charles L. Perrin wrote:
>
> It's a tradeoff between capacitive/inductive transmission losses
> (which are higher at higher frequencies) and the sizes of the
> transformers/filters.
>
> Also, if you get much below 50Hz, light bulbs tend to turn into strobe
> lights.
>
>
The resistance of a power transmission line wire at 400 Hz is 2.58 times
the resistance at 60 Hz due to skin effect (square root of frequency).
Bill W0IYH
Adam J. Thornton
The canonical work on the development of power grids is Thomas P. Hughes's
_Networks Of Power_. It's an excellent book.
Adam
--
ad...@phoenix.princeton.edu | Viva HEGGA! | Save the choad! | 64,928 | Fnord
"Double integral is also the shape of lovers curled asleep":Pynchon | Linux
Thanks for letting me rearrange the chemicals in your head. | Team OS/2
You can have my PGP passphrase when you pry it from my cold, dead brain.
Karl Quies
>
> Griff Hopkins wrote:
> >
> > Can anyone enlighten me on the history of 60Hz as the (U.S.)
> > 60Hz came about as a result of electric clocks (i.e.- the clocks
> > needed 60 cycles). While this makes sense (to ignorant me), it
> > certainly doesn't explain the use of 50Hz standards used by other
> > countries!?!?
> >
> > which to transfer power. Aviation electronics has been using
> > 400Hz for as long as I remember. At 400Hz, transformers and power
> > supply filters are significantly smaller. Also, EMF (low freq.
> > health) problems would seem to be greatly dimenished.
> >
> > Director of Engineering/
> > Primus Technology Group
>
over a distance of 500 or 1000 miles the inductive losses would be
too high. Even at 60 Herts the combined inductive and resistive
transmission losses approch 10 to !5%.
Canada prior to 1950 was 25 Hertz. Great for long distances but all
the Equipment was too bulky.
After the conversion we switched to 60 Hertz (rather then 50HZ).
The main reason beeing able to tie into the existing North American
power grid.
As a point of interest ASEA Electric in Sweden pioneered 500KV DC
transmission lines. That was 10-15 years ago. The inverting Equipment
at either end was the costly part. Might be cheaper now with P-Mos
Technology.
Karl
James Brooks
Griff Hopkins wrote:
>
> Can anyone enlighten me on the history of 60Hz as the (U.S.)
> standard line frequency. I seem to remember being taught that
> 60Hz came about as a result of electric clocks (i.e.- the clocks
> needed 60 cycles). While this makes sense (to ignorant me), it
> certainly doesn't explain the use of 50Hz standards used by other
> countries!?!?
>
> It would appear that 60Hz isn't the most efficient frequency at
> which to transfer power. Aviation electronics has been using
> 400Hz for as long as I remember. At 400Hz, transformers and power
> supply filters are significantly smaller. Also, EMF (low freq.
> health) problems would seem to be greatly dimenished.
>
> possible future trends for A.C. Power transfer. Thank you for
> your time.
>
> Director of Engineering/
> Primus Technology Group
An interesting side-note
If you ask someone in North America where 60Hz is the norm, to hum, they
will hum at 60Hz or the 2nd or 3rd harmonic of 60.
If you ask someone in Europe where 50Hz is the norm, to hum, they will
hum at 50Hz or the 2nd or 3rd harmonic of 50.
Yet another interesting use of PSYCHO-ACOUSTICS
Patrick Rea
Crisis Digital Productions
jbr...@interlog.com
Vincent Mulhollon
Griff Hopkins (75561...@CompuServe.COM) wrote:
: Can anyone enlighten me on the history of 60Hz as the (U.S.)
: standard line frequency. I seem to remember being taught that
: 60Hz came about as a result of electric clocks (i.e.- the clocks
: needed 60 cycles). While this makes sense (to ignorant me), it
: certainly doesn't explain the use of 50Hz standards used by other
: countries!?!?
Umm, no. Of course, if you took a electric clock BUILT for 60 Hz
and tried to run it on 50 Hz, time would really seem to crawl.
Also a record player would lower the key. But theres no necessity
to BUILD the clocks and stuff for 60 Hz.
: It would appear that 60Hz isn't the most efficient frequency at
: which to transfer power. Aviation electronics has been using
: 400Hz for as long as I remember. At 400Hz, transformers and power
: supply filters are significantly smaller. Also, EMF (low freq.
: health) problems would seem to be greatly dimenished.
Also at 400Hz hysteresis losses would go up by a factor of
about 400/60 and "slow speed" motors and the alternators at
the power company would need 400/60 more poles. Very expensive
and inefficent. Most electricity is used in big motors and
lighting and electrochemical processing so thats what the system
is designed for. Aircraft don't worry about electrical efficancy
and don't have a wide ranging power grid.
Luckily EMF health effects are about as strong as astrologic
effects, and affect the body about as much, so thats a non
issue.
: I would appreciate any enlightenment on the history, use, and
: possible future trends for A.C. Power transfer. Thank you for
: your time.
In the olden days before lightbulbs were popular and power supplies
hadn't been invented, and transformers weren't used much, only motors.
So some places used 25 Hz power because that gave the optimum
efficancy for motors.
I have no logical idea why some countries picked 50 Hz and some
picked 60 Hz. Probably just to be different.
--
Vince Mulhollon N9NFB
Henry Baker
> Can anyone enlighten me on the history of 60Hz as the (U.S.)
> standard line frequency. I seem to remember being taught that
> 60Hz came about as a result of electric clocks (i.e.- the clocks
> needed 60 cycles). While this makes sense (to ignorant me), it
> certainly doesn't explain the use of 50Hz standards used by other
> countries!?!?
>
> It would appear that 60Hz isn't the most efficient frequency at
> which to transfer power. Aviation electronics has been using
> 400Hz for as long as I remember. At 400Hz, transformers and power
> supply filters are significantly smaller. Also, EMF (low freq.
> health) problems would seem to be greatly dimenished.
There's a book called 'Electrifying America', by 'Nye', that touches
briefly on this issue. Apparently, > 60 Hz is best for electric lighting,
since it causes less flicker. On the other hand, the factory people wanted
< 60 Hz (probably multiphase) for their motors. Many early power plant
for industrial uses were DC, since DC motors were much easier to control
prior to semiconductor AC controllers.
Nye claims that 60 Hz was a compromise between lighting and industrial
users.
--
www/ftp directory:
ftp://ftp.netcom.com/pub/hb/hbaker/home.html
Charles L. Perrin
zzy...@mixcom.com (Vincent Mulhollon) wrote:
>Griff Hopkins (75561...@CompuServe.COM) wrote:
>: Can anyone enlighten me on the history of 60Hz as the (U.S.)
>: standard line frequency.
>: It would appear that 60Hz isn't the most efficient frequency at
>: which to transfer power. Aviation electronics has been using
>: 400Hz for as long as I remember. At 400Hz, transformers and power
>: supply filters are significantly smaller.
>Also at 400Hz hysteresis losses would go up by a factor of
>about 400/60 and "slow speed" motors and the alternators at
>the power company would need 400/60 more poles. Very expensive
>and inefficent. Most electricity is used in big motors and
>lighting and electrochemical processing so thats what the system
>is designed for. Aircraft don't worry about electrical efficancy
>and don't have a wide ranging power grid.
Aircraft don't worry about electrical efficiency? Well, they have to
LIFT all their generators, motors, and wiring. So, they DEFINITELY
worry about the weight of all that equipment.
Spacecraft are even worse.
sokos mark
>Nye claims that 60 Hz was a compromise between lighting and industrial
>users.
I was told that 60 Hz originally gained its popularity because the
first major showing* of these systems ran at 50 Hz, but when they
went to actually run it they couldn't get quite enough power out of
it and cranked the generators to 60 Hz to compensate. The 60 Hz
stuck for many of the early systems, and for reasons probably more
political than practical, ended up being the standard.
Many of the other reasons mentioned (high enough that it does not
cause lights to flicker, low enough that audio interference is
minimal) were also major influences, but the actual 50 vs. 60
was more due to the above than anything else.
True, or folklore? I got it from an old power engineer while I
worked at a power plant.
* - Possibly at a world's fair? This was way before my time, so
I certainly don't remember.
- Mark Sokos (mso...@gl.umbc.edu) http://www.gl.umbc.edu/~msokos1
Electrical engineer, computer geek (er, programmer) in training,
no-talent bum musician (have bass, will travel), and perpetual student
Douglas W. Jones,201H MLH,3193350740,3193382879
High frequency power allows smaller transformers (weight savings) but
incurs eddy current losses.
In long distance transmission, high frequency leads to more radiative
loss -- power leaks out of the wires as radio waves and doesn't arrive
at the destination. Thus, if you want to transmit lots of power over
long distances, use DC or low frequency AC.
High efficiency low frequency motors are relatively easy to build.
Achieving the same power to weight ratio at comparable efficiency is
difficult at high frequencies. Your commonplace "universal" motor, as
found in many common motorized applications is not really universal.
It only works well at low frequency.
So, the frequency we use is a compromize. 60 Hz is common in the
Americas, 50 Hz in Europe, and railroad electrification has used frequencies
as low as 18 Hz (20 Hz was once common). Railroads find motor efficiency
to be of primary concern -- the eddy current losses at 60 Hz were once
seen as too much, and adding to the engine weight with a big transformer
only reduces the amount of ballast they need to add in order to avoid
slipping.
Neither the common power grid nor the special power grids of the railroads
can afford the radiative losses we'd suffer at 400 Hz for long distance
transmission, and until recently, we couldn't afford routine frequency
conversion. But, outside of railroads and stationary power in places like
steel mills, we want things to be relatively lightweight, so we use a
midrange frequency. There's nothing particularly optimal about either
50 or 60 Hz, but both are reasonable.
The folks who build airplanes don't give a hoot about long-distance
transmission efficiency, and they're not into the kind of huge continuous
duty motors where eddy current losses are a big issue. What they do care
about is weight, and transformer weight was once a big issue in the days
of vacuum tube avionics and high plate voltages.
So, why precisely 60 Hz, or why precisely 50? Why not 40 or 70? That's
where arguments like the one about clockmakers may actually hold water.
Doug Jones
jo...@cs.uiowa.edu
John Lundgren
Griff Hopkins (75561...@CompuServe.COM) wrote:
: Can anyone enlighten me on the history of 60Hz as the (U.S.)
: needed 60 cycles). While this makes sense (to ignorant me), it
: certainly doesn't explain the use of 50Hz standards used by other
: countries!?!?
: It would appear that 60Hz isn't the most efficient frequency at
: which to transfer power. Aviation electronics has been using
: 400Hz for as long as I remember. At 400Hz, transformers and power
: supply filters are significantly smaller. Also, EMF (low freq.
: health) problems would seem to be greatly dimenished.
Actually the transformers, etc, are significantly lighter. The size
wasn't the problem.
But it is significantly harder to get a big generator to spin 7 times
faster to get 400 Hz. It would probably fly apart. Remember that these
are giant generators inside dams and in steam plants, and they are not
concerned about weight.
And the BIG problem is that it is significantly *harder* to filter out
400 Hz from audio amps or whatever. That's right in the middle of the
audio passband.
As for low frequency health problems, they are _already_ diminished.
After working on RADARS in the army, I would never want to go back to
listening to that constant irritating WHINE of 400 Hz blowers.
: I would appreciate any enlightenment on the history, use, and
: possible future trends for A.C. Power transfer. Thank you for
: your time.
: Griff Hopkins
: Director of Engineering/
: Primus Technology Group
--
#======P=G=P==k=e=y==a=v=a=i=l=a=b=l=e==u=p=o=n==r=e=q=u=e=s=t======#
| John Lundgren - Elec Tech - Info Tech Svcs. | jlundgre@ |
| Rancho Santiago Community College District | deltanet.com |
| 17th St at Bristol \ Santa Ana, CA 92706 | http://www.rancho|
| My opinions are my own, and not my employer's. | .cc.ca.us |
| Most FAQs are available through Thomas Fine's WWW FAQ archive: |
|http://www.cis.ohio-state.edu:80/hypertext/faq/usenet/FAQ-List.html|
| "You can flame your brains out -- it won't take long." |
#===T=u=z=l=a==C=o=m=p=a=n=y=.=.===t=h=r=e=e='=s==L=e==C=r=o=w=d=!==#
Andy Shiekh
In article <31E903...@crpl.cedar-rapids.lib.ia.us>, "William E. Sabin"
<sab...@crpl.cedar-rapids.lib.ia.us> wrote:
How do you figure this?
If the line is thinner than either skin depth,
then the calculation does not hold.
Andy Shiekh
> But it is significantly harder to get a big generator to spin 7 times
> faster to get 400 Hz. It would probably fly apart. Remember that these
> are giant generators inside dams and in steam plants, and they are not
> concerned about weight.
As was pointed out to me,
spin speed is not a problem,
as one can go multi-pole
z807...@dial.pipex.com
>The resistance of a power transmission line wire at 400 Hz is 2.58 times
>the resistance at 60 Hz due to skin effect (square root of frequency).
Nonsense.
Skin effect applies only at the surface of a conductor, and is
significant only at the 100's of MHz area and above. At 400Hz it is
totally and utterly insignificant.
Peter
>Also at 400Hz hysteresis losses would go up by a factor of
>about 400/60 and "slow speed" motors and the alternators at
>the power company would need 400/60 more poles. Very expensive
>and inefficent. Most electricity is used in big motors and
>lighting and electrochemical processing so thats what the system
>is designed for. Aircraft don't worry about electrical efficancy
>and don't have a wide ranging power grid.
I recently discussed this with a manufacturer of power station
generators.
The chief problem there is the compromise between the RPM of the steam
turbine (which needs to be as high as possible, for thermodynamic
reasons) and the need to generate frequency at *only* 50/60 Hz.
To get 50Hz, you make a two-pole generator (not possible to have fewer
poles than 2) and run it at 3000 RPM. For 60Hz, you run it at 3600 RPM
which is better.
One cannot use a gearbox because of mechanical problems and losses.
Generating much higher frequencies is easy, e.g. a 20-pole generator
running at 3000 RPM would give you 500Hz.
The problems would be elsewhere, with higher hysteresis losses etc.
However, I would think that since the magnetics would be much smaller,
one could afford to use higher grade materials.
But this is hypothetical, since one can never change.
Peter.
Bob
Try reading "Tesla: Man out of Time" by Margaret Cheney. Funny how so
many people can discuss what is essentially the "Tesla Polyphase System"
without crediting the inventor of same and of alternating current and a-c
motors and generators!!! The gall!
BOB
AV3J
In the newsgroup, alt. engineering. electrical, the question of how 60 Hz
was decided upon has been discussed quite a bit the last couple of weeks
after this questions was posted:
>Hi there...
>I am trying desparately to figure out why we use 60Hz electric power. I
know why >its >around 60, i.e. a nice compromise between the skin effect
and transformer size, etc., >but someone chose 60 (and not 64, 50, 72,
etc.) and I would like to know who and >why. I don't believe its because
electric motors run at 3600 RPM, because you could >run a motor at 4000
RPM and just gear it differently. If it were me, I think I would have
>chosen 64Hz because it has a nice square root, cube root, etc., for clean
>computations.
>Was it Westinghouse? Edison (I doubt it)? Nikkola Tesla? and why?
>Please E-mail copies of all responses, I don't read the newsgroup
regularly...
>Thanks!
>-M.E. Ingoldsby
Those interested might wish to read for additional views.
J.Jones
Thomas A Maier
I don't know about the skin effect at 400Hz, I guess I never thought
about that.
It was my understanding that the major reason for the 400 Hz in aircraft
was just to reduce the weight of the iron required in transformers,
motors and alternators.
Dave Keith
In article <4sd0dg$m...@sjx-ixn2.ix.netcom.com>, mano...@aol.com says...
Yes, take Bobs advice. "Man Out Of Time" is an excellent book and while
it won't satisy any desires to settle technical arguments about skin effect,
it will inform you about the politics surrounding the electrification of
USA and the battles between Edison and Tesla/Westinghouse. Very interesting.
dave
Thomas A Maier
I actually did that as a kid. I connected a signal generator to an
antenna via a carbon mike from a telephone handset. It probably
resulted in .001% modulation but my buddy down the street could pick it
up.
Tom, K3WFN
Douglas W. Jones,201H MLH,3193350740,3193382879
From article <4sd0lb$k...@news02.deltanet.com>,
by jlun...@delta1.deltanet.com (John Lundgren):
>
> I don't understand why so many people have remarked that the conversion
> would be better with MOS devices. I've seen SCRs the size of coffee cups
> that handle hundreds of volts or more and 1200 amps or more.
These are whole wafer devices, and are sometimes referred to as
"hockey puck" format SCR's. For some applications, they stack them
up to greater than coffee cup dimensions.
> Karl Quies (ka...@io.org) wrote:
>
> 400Hz is fine in a plane but try to send several hundred mega watts
> over a distance of 500 or 1000 miles the inductive losses would be
> too high. Even at 60 Herts the combined inductive and resistive
> transmission losses approch 10 to !5%.
About 25 years ago, the H2indenberg Society (an early group devoted to
pushing the notion of the Hydrogen fuel economy) noted that, with the
electrolyzer technology of the 1960's and with conventional combustion
power plants, long distance power transmission, even using high voltage
DC, was less effective than electrolysis, a pipeline, and a power plant
at the far end, for distances of over 500 miles.
Furthermore, that 500 mile pipeline completely isolates the source-end
power plant from the customer's peaking demands. So, at the head end
of the pipe, you can electrolyze water with off-peak power, and at the
consumer's end, you can augment your primary boiler-steam-turbine plant
with hydrogen-gas-turbine peaking generators whenever needed.
A nice idea, but nobody's done much in the way of followup.
Doug Jones
jo...@cs.uiowa.edu
Stephen Schiller
William E. Sabin wrote:
>
> Andy Shiekh wrote:
> >
> > In article <31E903...@crpl.cedar-rapids.lib.ia.us>, "William E. Sabin"
> > <sab...@crpl.cedar-rapids.lib.ia.us> wrote:
> >
> >times the resistance at 60 Hz due to skin effect (square root of
> >frequency).
>
> >
> > If the line is thinner than either skin depth,
> > then the calculation does not hold.
>
> the ratio is not exactly according to the square root, as I said. I stand
> corrected on that. Instead, a very complicated formula involving complex
> Bessel functions is involved (see W.C. Johnson "Transmission Lines and
> Networks" McGraw-Hill, 1950). Although my 2.58 number is not exactly
> right, nevertheless skin effect would be an important factor, and for a
> high power line with large conductors my 2.58 number might even be too
> small. There is also an internal *inductance* effect inside the wire that
> affects the transmission line properties. Radiation loss would also be a
> factor.
>
> Bill W0IYH
To make Bill's argument more concrete:
The skin depth at 60Hz is about 1cm (for copper -- would be slightly
larger for aluminum). The skin depth at 400Hz is about 4mm. I could
easily see high power lines being 1cm or more thick. The reason it
is not usually necessary to consider the skin effect until you get
up to the 100MHz range is that even though has a significant effect
at lower frequencies, copper is such a good conductor that the
resistance of wires is still not affected much.
- Stephen Schiller
William E. Sabin
z807...@dial.pipex.com wrote:
>
> >The resistance of a power transmission line wire at 400 Hz is 2.58 times
> >the resistance at 60 Hz due to skin effect (square root of frequency).
>
>
> Skin effect applies only at the surface of a conductor, and is
> significant only at the 100's of MHz area and above. At 400Hz it is
> totally and utterly insignificant.
It is not nonsense, and you should review "skin effect"
Harry H Conover
Griff Hopkins (75561...@CompuServe.COM) wrote:
: Can anyone enlighten me on the history of 60Hz as the (U.S.)
: standard line frequency. I seem to remember being taught that
: 60Hz came about as a result of electric clocks (i.e.- the clocks
: needed 60 cycles). While this makes sense (to ignorant me), it
: certainly doesn't explain the use of 50Hz standards used by other
: countries!?!?
Well, no. You could design an electric clock to operate at
almost any frequency. It becomes simply a question of gear ratios.
: It would appear that 60Hz isn't the most efficient frequency at
: which to transfer power. Aviation electronics has been using
: 400Hz for as long as I remember. At 400Hz, transformers and power
: supply filters are significantly smaller. Also, EMF (low freq.
: health) problems would seem to be greatly dimenished.
Actually, much of aviation electronics uses 800-Hz power (along, of
course, 400-Hz.) I've not sure of the exact trade-off decision made
here, but I would assume it to be in the direction of optimizing
(reducing) weight. 400 and 800-Hz transformer require considerably
less core material, and are correspondingly lighter, than would be
say 60-Hz designs. (As a kid, I remember trying to kludge together
something supply a war surplus, airborne APS-3 radar system with
115V 800-Hz power, but having only limited success.)
Efficiency is altogether another matter.
Transmission line loss increases with frequency (without consulting
a text I don't recall if it inclreases linearly with frequency, or
possibly at a power of the frequency.) At any rate, it has been
long established that maximum transmission line efficiency happens
at 0-Hz or DC. Anything above 0-Hz results in radiation (and other)
line losses that decrease line efficiency.
Transformer losses tend to increase with increasing frequency
(both hysteresis and eddy current losse), so this is another reason
why transmission system design prefers the lowest possible frequency.
I'm not sure of why specifically 60-Hz was selected, but suspect it was
the result of a trade-off of transmission line efficiency vs. transformer
(size, weight, loss, and power factor) design considerations.
Harry C.
:
John Lundgren
James Brooks (jbr...@interlog.com) wrote:
: Griff Hopkins wrote:
: >
: > Can anyone enlighten me on the history of 60Hz as the (U.S.)
: > standard line frequency. I seem to remember being taught that
: > 60Hz came about as a result of electric clocks (i.e.- the clocks
: > needed 60 cycles). While this makes sense (to ignorant me), it
: > certainly doesn't explain the use of 50Hz standards used by other
: > countries!?!?
: > which to transfer power. Aviation electronics has been using
: > 400Hz for as long as I remember. At 400Hz, transformers and power
: > supply filters are significantly smaller. Also, EMF (low freq.
: > health) problems would seem to be greatly dimenished.
: > I would appreciate any enlightenment on the history, use, and
: > possible future trends for A.C. Power transfer. Thank you for
: > your time.
: >
: > Griff Hopkins
: > Director of Engineering/
: > Primus Technology Group
: An interesting side-note
: If you ask someone in North America where 60Hz is the norm, to hum, they
: will hum at 60Hz or the 2nd or 3rd harmonic of 60.
: If you ask someone in Europe where 50Hz is the norm, to hum, they will
: hum at 50Hz or the 2nd or 3rd harmonic of 50.
: Yet another interesting use of PSYCHO-ACOUSTICS
Most people do not have perfect or relative pitch so I don't believe you
could say this in general. It might apply to those who do, tho.
: Patrick Rea
: Crisis Digital Productions
: jbr...@interlog.com
--
#===================================================================#
| John Lundgren - Elec Tech - Info Tech Svcs. | jlundgre@ |
| Rancho Santiago Community College District | deltanet.com |
| 17th St at Bristol \ Santa Ana, CA 92706 | http://www.rancho|
| My opinions are my own, and not my employer's. | .cc.ca.us |
| Most FAQs are available through Thomas Fine's WWW FAQ archive: |
|http://www.cis.ohio-state.edu:80/hypertext/faq/usenet/FAQ-List.html|
| "Babe Ruth struck out 1,330 times... keep on swinging." |
| says the lid on the jar of Laredo & Lefty's Picante Sauce |
#======P=G=P==k=e=y==a=v=a=i=l=a=b=l=e==u=p=o=n==r=e=q=u=e=s=t======#
William E. Sabin
On long, high current transmission lines, skin effect is very important,
even at 60 Hz. It's my understanding that a *hollow* conductor with a
nonconducting core is sometimes used in power transmission, partly also
to help reduce corona effects. Does anyone know something about that?
Bill
William E. Sabin
>
> The resistance of a power transmission line wire at 400 Hz is 2.58
>times the resistance at 60 Hz due to skin effect (square root of
>frequency).
> How do you figure this?
Chris Woodrow
Douglas W. Jones,201H MLH,3193350740,3193382879 wrote:
>
> From article <31EA7A...@crpl.cedar-rapids.lib.ia.us>,
> by "William E. Sabin" <sab...@crpl.cedar-rapids.lib.ia.us>:
> >
> > On long, high current transmission lines, skin effect is very important,
> > even at 60 Hz. It's my understanding that a *hollow* conductor with a
> > nonconducting core is sometimes used in power transmission, partly also
> > to help reduce corona effects. Does anyone know something about that?
>
> Many high-tension lines have bundles of 3 or 4 conductors, spaced about
> a foot apart and held apart by "spiders" to make each "wire". A single
> insulator suspends the bundle from each tower.
This is mainly to reduce inductance, not skin effect.
>
> Another classic reaction to the skin effect problem is to use copper
> clad steel wire. The low resistance metal is used only for the skin,
> while the high tensile strength metal is used for the body, thus allowing
> a longer inter-tower spacing. Do they do this with aluminum too?
The most common is ACSR (Aluminum conductor steel reinforced). With steel
stranding on the inside and aluminum stranding on the outside. The main
purpose of the steel is to provide strength for longer spans.
>
> But, another problem with high frequency long-distance transmission is
> radiative loss. At 60 cycles this is a problem; they solve it by
> "twisting" the transmission line (we use the same trick with twisted pair
> wires, on a smaller scale). Twists in high-tension lines are not done
> continuously; instead, every few miles, there's a special tower or tower
> pair that rotates the wires. For a 3-wire line where all 3 are normally
> carried horizontally (left, center, right), the right line might dive
> down to the bottom position on the "twist" tower, then come up on the
> left while the center wire shifts to the right and the right wire shifts
> to the center.
>
I don't think tranposition reduces inductance much, it just makes it even
across all three phases so that the voltages are in balance.
> The spacing between these twist points depends on the wavelength. The
> higher the frequency, the more frequently you need to twist the line in
> order to prevent radiation. Each twist costs money -- special towers and
> a break in the easy "straight line" wire stringing process.
>
> Doug Jones
> jo...@cs.uiowa.edu
Is this going in the Guinness Book of Records as the worlds longest thread?
If so, I wanted to be included.
Chris Woodrow
John Lundgren
Karl Quies (ka...@io.org) wrote:
: >
: > Griff Hopkins wrote:
: > >
: > > Can anyone enlighten me on the history of 60Hz as the (U.S.)
: > > standard line frequency. I seem to remember being taught that
: > > 60Hz came about as a result of electric clocks (i.e.- the clocks
: > > needed 60 cycles). While this makes sense (to ignorant me), it
: > > certainly doesn't explain the use of 50Hz standards used by other
: > > countries!?!?
: > >
: > > It would appear that 60Hz isn't the most efficient frequency at
: > > which to transfer power. Aviation electronics has been using
: > > 400Hz for as long as I remember. At 400Hz, transformers and power
: > > supply filters are significantly smaller. Also, EMF (low freq.
: > > health) problems would seem to be greatly dimenished.
: > >
: > > Director of Engineering/
: > > Primus Technology Group
: >
: over a distance of 500 or 1000 miles the inductive losses would be
: too high. Even at 60 Herts the combined inductive and resistive
: transmission losses approch 10 to !5%.
Remember that an inductor does not have any losses (ideally).
: Canada prior to 1950 was 25 Hertz. Great for long distances but all
: the Equipment was too bulky.
: After the conversion we switched to 60 Hertz (rather then 50HZ).
: The main reason beeing able to tie into the existing North American
: power grid.
Actually it probably meant that the Canadians could suck some of that
juice from the Niagara falls without converting.
: As a point of interest ASEA Electric in Sweden pioneered 500KV DC
: transmission lines. That was 10-15 years ago. The inverting Equipment
: at either end was the costly part. Might be cheaper now with P-Mos
: Technology.
I don't understand why so many people have remarked that the conversion
would be better with MOS devices. I've seen SCRs the size of coffee cups
that handle hundreds of volts or more and 1200 amps or more. I haven't
heard of that kind of power using MOS devices. There really doesn't
seem to be a need for them when SCRs will do the job. (Or TRIACs)
: Karl
William E. Sabin
Douglas W. Jones,201H MLH,3193350740,3193382879 wrote:
>
> More often, they solve the skin effect problem with a group of conductors.
> Many high-tension lines have bundles of 3 or 4 conductors, spaced about
> a foot apart and held apart by "spiders" to make each "wire". A single
> insulator suspends the bundle from each tower.
>
> clad steel wire. The low resistance metal is used only for the skin,
> while the high tensile strength metal is used for the body, thus allowing
> a longer inter-tower spacing. Do they do this with aluminum too?
>
> radiative loss. At 60 cycles this is a problem; they solve it by
> "twisting" the transmission line (we use the same trick with twisted pair
> wires, on a smaller scale). Twists in high-tension lines are not done
> continuously; instead, every few miles, there's a special tower or tower
> pair that rotates the wires. For a 3-wire line where all 3 are normally
> carried horizontally (left, center, right), the right line might dive
> down to the bottom position on the "twist" tower, then come up on the
> left while the center wire shifts to the right and the right wire shifts
> to the center.
>
> higher the frequency, the more frequently you need to twist the line in
> order to prevent radiation. Each twist costs money -- special towers and
> a break in the easy "straight line" wire stringing process.
>
> Doug Jones
> jo...@cs.uiowa.edu
Very interesting info. We hams use copper-clad steel wire for HF
antennas and it works quite well. At 1.8 MHz the skin depth is about
0.002 inches.
Bill W0IYH
William E. Sabin
Chris Woodrow wrote:
>
> This is mainly to reduce inductance, not skin effect.
>
The transposing is done to reduce radiation by virtue of field
cancellation.
Bill
Douglas W. Jones,201H MLH,3193350740,3193382879
From article <31EA7A...@crpl.cedar-rapids.lib.ia.us>,
by "William E. Sabin" <sab...@crpl.cedar-rapids.lib.ia.us>:
>
> On long, high current transmission lines, skin effect is very important,
> even at 60 Hz. It's my understanding that a *hollow* conductor with a
> nonconducting core is sometimes used in power transmission, partly also
> to help reduce corona effects. Does anyone know something about that?
More often, they solve the skin effect problem with a group of conductors.
Bruce Bostwick
> there was a brief flurry of activity using alternators to produce RF power
> directly for broadcast AM radio. I forget how they modulated it, possibly
> by running the audio signal through the alternator's field windings.
> That would mean that your entire circuit for an AM broadcast transmitter
> would consist of a battery, carbon button microphone and alternator field
> winding in series, with the output of the alternator wired directly to the
> antenna.
I believe this was for shipboard radio transmitters, and the alternator didn't
generate the RF. The RF was generated by an arcane LC network powered by the
alternator, whose audio-frequency AC provided a more or less clean tone for the
transmitter. It only worked for code, of course (this was in the *early* days,
folks!) although the transmitters were capable of many kilowatts. The antenna
was a long hard-drawn copper (?) wire running from the bow to the stern and
across the tops of the masts, and the wireless room was a Faraday cage. It was a
scary place to be, as I understand it, and was the origin of the radio operator's
nickname "Sparky" -- the code key was a lively bug indeed. ;-)
They did actually have 'phone transmitters back then, but they used *RELAYS*,
believe it or not, to modulate the RF. These were cantankerous and unreliable
instruments to say the least .. the triode was a welcome innovation. I've also
heard that some of the early audion detectors used a Bunsen burner flame instead
of a vacuum ...
--
<BGB> http://ccwf.cc.utexas.edu/~lihan/ mailto:li...@ccwf.cc.utexas.edu
Douglas W. Jones,201H MLH,3193350740,3193382879
From article <31e97361...@news.dial.pipex.com>,
by ft...@dial.pipex.com (Peter):
> To get 50Hz, you make a two-pole generator (not possible to have fewer
> poles than 2) and run it at 3000 RPM. For 60Hz, you run it at 3600 RPM
> which is better.
> Generating much higher frequencies is easy, e.g. a 20-pole generator
> running at 3000 RPM would give you 500Hz.
It's worth noting that, before the advent of successful RF vacuum tubes,
there was a brief flurry of activity using alternators to produce RF power
directly for broadcast AM radio. I forget how they modulated it, possibly
by running the audio signal through the alternator's field windings.
That would mean that your entire circuit for an AM broadcast transmitter
would consist of a battery, carbon button microphone and alternator field
winding in series, with the output of the alternator wired directly to the
antenna.
Doug Jones
jo...@cs.uiowa.edu
Earl Kiosterud
In article <31E951...@interlog.com>,
James Brooks <jbr...@interlog.com> wrote:
>Griff Hopkins wrote:
>>
>> Can anyone enlighten me on the history of 60Hz as the (U.S.)
>> standard line frequency.
>> Griff Hopkins
>> Director of Engineering/
>> Primus Technology Group
>
>
>If you ask someone in North America where 60Hz is the norm, to hum, they
>will hum at 60Hz or the 2nd or 3rd harmonic of 60.
>
>If you ask someone in Europe where 50Hz is the norm, to hum, they will
>hum at 50Hz or the 2nd or 3rd harmonic of 50.
>Yet another interesting use of PSYCHO-ACOUSTICS
>jbr...@interlog.com
Most devices that emit an audible hum (motors, etc) do so at twice the 60 Hz.
frequency. So we don't really hear a second harmonic; 120 Hz. is the
fundamental frequency being radiated. This is because each half-cycle of the
60 Hz. wave produces one complete cycle of vibration. Removing the magnet
from a speaker would cause the same thing to happen (to the extent the the
speaker still worked at all!).
FWIW.
Earl K. Virginia Beach, VA ea...@livenet.net
Charles L. Perrin
jo...@pyrite.cs.uiowa.edu (Douglas W. Jones,201H
MLH,3193350740,3193382879) wrote:
>It's worth noting that, before the advent of successful RF vacuum tubes,
>there was a brief flurry of activity using alternators to produce RF power
>directly for broadcast AM radio. I forget how they modulated it, possibly
>by running the audio signal through the alternator's field windings.
>That would mean that your entire circuit for an AM broadcast transmitter
>would consist of a battery, carbon button microphone and alternator field
>winding in series, with the output of the alternator wired directly to the
>antenna.
I remember reading about one experiment where they put the carbon
button mike in series between the alternator and the antenna. (They
had a special one designed for water cooling.)
--------------------------------------------------------------
Charlie's Sneaker Pages: http://sneakers.pair.com/
Best Value in Airplanes: http://www.boeing.com/
--------------------------------------------------------------
Sir Spamalot
On Sun, 14 Jul 1996 07:25:29 -0700, "William E. Sabin"
<sab...@crpl.cedar-rapids.lib.ia.us> wrote:
--->Charles L. Perrin wrote:
--->>
--->
--->> It's a tradeoff between capacitive/inductive transmission
losses
--->> (which are higher at higher frequencies) and the sizes of
the
--->> transformers/filters.
--->>
--->> Also, if you get much below 50Hz, light bulbs tend to turn
into strobe
--->> lights.
--->>
--->>
--->
--->The resistance of a power transmission line wire at 400 Hz is
2.58 times
--->the resistance at 60 Hz due to skin effect (square root of
frequency).
--->
--->Bill W0IYH
Then, why not 10Hz????
Ralph Wade Phillips
Hi there!
In article <31e97209...@news.dial.pipex.com>,
z807...@dial.pipex.com wrote:
> >The resistance of a power transmission line wire at 400 Hz is 2.58 times
> >the resistance at 60 Hz due to skin effect (square root of frequency).
>
> Nonsense.
>
> Skin effect applies only at the surface of a conductor, and is
> significant only at the 100's of MHz area and above. At 400Hz it is
> totally and utterly insignificant.
(cough cough) At megawattage levels, it's MINOR, but !NOT!
insignificant.
Kind of like checking SWR's - on a CB set (5w input, 4w output), a
1.2 or 1.3 SWR is peachy-keen (you won't see but maybe a .01db output
improvement going to 1.1 from a 1.3 SWR). !BUT! - When it's a 10Megawatt
RADAR pulse, that 1.2SWR will reflect back 200KW. !THAT!'s far from
insignificant ...
RwP
--
Ralph Wade Phillips, CET #LA-82
ral...@gcstation.net
William E. Sabin
Stephen Schiller wrote:
>
> To make Bill's argument more concrete:
> The skin depth at 60Hz is about 1cm (for copper -- would be slightly
> larger for aluminum). The skin depth at 400Hz is about 4mm. I could
> easily see high power lines being 1cm or more thick. The reason it
> is not usually necessary to consider the skin effect until you get
> up to the 100MHz range is that even though has a significant effect
> at lower frequencies, copper is such a good conductor that the
> resistance of wires is still not affected much.
>
Not true. The *resistance of the wire*, even a large wire, increases as
the square root of frequency. This effect is especially noticed in RF
coax cables at all HF frequencies. It is also noticed at 60 Hz. It is
definitely not true that we don't think of skin effect below 100 MHz.
There is a kind of stranded wire, called Litz wire, that was designed to
reduce skin effect in the 1 kHz to 3 MHz range.
Bill W0IYH
Chris Woodrow
Chris Woodrow
Brendan Kirby wrote:
> not inductance. It also increases current capacity.
> --
>
> Brendan Kirby
> Oak Ridge National Lab
>
> B...@ORNL.GOV
It is done for both reasons. I quote from "Elements of Power Systems Analysis" ..
"... Reduced reactance is the other equally important advantage of bundling."
Chris Woodrow
c...@ornl.gov
Mike658
Griff Hopkins wrote:
>
> Can anyone enlighten me on the history of 60Hz as the (U.S.)
> 60Hz came about as a result of electric clocks (i.e.- the clocks
> needed 60 cycles). While this makes sense (to ignorant me), it
> certainly doesn't explain the use of 50Hz standards used by other
> countries!?!?
>
> It would appear that 60Hz isn't the most efficient frequency at
> which to transfer power. Aviation electronics has been using
> 400Hz for as long as I remember. At 400Hz, transformers and power
> supply filters are significantly smaller. Also, EMF (low freq.
> health) problems would seem to be greatly dimenished.
>
> possible future trends for A.C. Power transfer. Thank you for
> your time.
>
> Director of Engineering/
> Primus Technology Group
After reading this entire thread and doing a little research of my own, I
think the best explanation for the 60hz decision was the one about
originally using 50hz and then having to crank it up to get a little more
power.
While they do exits, skin losses and radiative losses are not
substantial at power line frequencies.
Aircraft power probably uses 400 hz as a result of the high source
(turbine) frequencies. It is probably a compromise designed to reduce
losses involved in coming all the way down to 60 hz.
--
Michael Gaithersburg. Maryland
(mik...@ibm.net)
(micha...@worldnet.att.net)
dave pierson
In article <4s97l3$r6s$1...@mhadg.production.compuserve.com>, Griff Hopkins
<75561...@CompuServe.COM> writes...
>Can anyone enlighten me on the history of 60Hz as the (U.S.)
>standard line frequency.
The history was pretty well covered by the IEEE about 15 years ago when
someone decided to celebrate 100 years of electric power. Check
"Spectrum" from around then.
For REALLY DEEP discussion, olde copies IEEE (and AIEE, predecessor
organization) "Transactions". Like Vol I, etc...
>I seem to remember being taught that 60Hz came about as a result of electric
>clocks (i.e.- the clocks needed 60 cycles).
The clocks need a constant freq. they could care less WHAT.
60 Hz (by all acounts) was picked by Nikola Tsla, then consulting for
Westinghouse. All manners of freqs had been tried, as low as 15 or
so and as high as 180. Driving factors were:
fast enough not to flicker lights.
slow enough for low eddy current losses to be low.
(The last changes, over time, as steels get trickier.)
US standardized on 60 Hz for 'lighting and other' and 25 Hz for
'motor load' (for specialized large motors. Where size is no
object, a relatively LOW freq was more efficient, given the
steels.)
(Reportedly, Tesla simply liked the progression: 60 minutes in an hour.
60 seconds in a minute, 60 cycles in a second...)
>While this makes sense (to ignorant me), it certainly doesn't explain the use
>of 50Hz standards used by other countries!?!?
In a technical sense it doesn't make any diif, so long as it is fast
enough not to flicker th lights.
>It would appear that 60Hz isn't the most efficient frequency at
>which to transfer power.
It would appear it is. (plus or minus 20 %)
>Aviation electronics has been using 400Hz for as long as I remember.
See IEEE transactions just pre WWII and during for history.
>At 400Hz, transformers and power supply filters are significantly smaller.
And More Expensive (more expensive steels....) In a/c work, WEIGHT and
SIZE efficiency are more important than COST efficiency. Think of a
world where all the power transformers 'hummmmed' at 400 Hz....
>Also, EMF (low freq. health) problems would seem to be greatly dimenished.
If There Are Any Such Risks.
and
IF they are unique to 50/60 Hz
(Hint: I have been watch ELF health debate for 2 decades. I remain
unconvinced of risk...)
thanks
dave pierson |the facts, as accurately as i can manage,
Digital Equipment Corporation |the opinions, my own.
334 South St |this space left blank
Shrewsbury, Mass 01545 |pie...@cimcad.enet.dec.com
"He has read everything, and, to his credit, written nothing." A J Raffles
Brendan Kirby
I'll get this right in a day or two.
Of course the line reactance goes down with increased equivalent
conductor diameter, as you said. So the only disadvantage to bundling is
complexity/cost.
Sorry about that.
Brendan Kirby <b...@ornl.gov> wrote:
>Hi Chris,
>
>Checking the venerable old Westinghouse T&D book I was surprised to find
>that the Xa term (inductance from the equivalent conductor diameter) is
>more significant than I had recalled. So while corona forces you to split
>the phase conductor into a bundle above about 230KV inductance as well as
>complexity lead you to prefer to use a single conductor when you can.
>
>Thanks!
>
dho...@psl.wisc.edu
In article <4sgick$1...@nntpd.lkg.dec.com>, pie...@ggone.enet.dec.com (dave pierson) writes:
>In article <4s97l3$r6s$1...@mhadg.production.compuserve.com>, Griff Hopkins
><75561...@CompuServe.COM> writes...
>
>>I seem to remember being taught that 60Hz came about as a result of electric
>>clocks (i.e.- the clocks needed 60 cycles).
> The clocks need a constant freq. they could care less WHAT.
> 60 Hz (by all acounts) was picked by Nikola Tsla, then consulting for
> Westinghouse. All manners of freqs had been tried, as low as 15 or
While I'm sure 60 Hz was chosen long before synchronous clocks became
popular, synchronous clocks were a big motivator in getting the power
companies to maintain well-regulated (average) frequency. Henry Warren
(Telechron) had to convince the power companies that they could make
money selling a few watts of electricity to each clock owner; then
he could sell his regulating clocks (which showed the difference between
an accurate pendulum clock time and a synchronous clock time, so they
could regulate the power frequency) to the power companies; then he
could sell his synchronous clocks to households. Before this the
power companies did not regulate their frequency to the point where
it could be used to keep good time.
>>While this makes sense (to ignorant me), it certainly doesn't explain the use
>>of 50Hz standards used by other countries!?!?
[..]
I think 50 Hz was reasonably popular in the U.S. also. I remember
reading about Los Angeles switching over from 50 Hz to 60 Hz when they
were about to be connected to a hydro power plant in (I think) the
early thirties. The city arranged for a central site where everyone
could bring their (portable) clocks to have them modified for 60 Hz
if feasible, or replaced if modification weren't feasible. The city
also sent people around the city to modify clocks that were too big
to move. They ended up with a big pile of 50 Hz clocks which were
dumped in the ocean.
e
I wonder whether the power companies have a better idea of why they do the
things they do concerning power distribution than those involved in this
"history" thread. Funny that for something apparently well understood (I
say this as someone still learning E&M basics) there can be so many
differing ideas and necessary clarifications; I guess that is why I like
science.
Travis...
Karl Quies
>
> Remember that an inductor does not have any losses (ideally).
>
and all that useless current circulating out of Phase through the
'ideal' inductor creates resistive losses in the 1000 miles of wire
used.
> : Canada prior to 1950 was 25 Hertz. Great for long distances but
all
> : the Equipment was too bulky.
>
> : After the conversion we switched to 60 Hertz (rather then 50HZ).
> : The main reason beeing able to tie into the existing North
> American
> : power grid.
>
> Actually it probably meant that the Canadians could suck some of that
> juice from the Niagara falls without converting.
>
Good Yankee Attitude!!!
To my knowledge Canada has been a net exporter of power to the USA
for quite a while.
By the way. Who wants to 'suck' all the Water that they can get
out of British Columbia to irrigate the California Valley ?
>
> I don't understand why so many people have remarked that the
conversion
> would be better with MOS devices. I've seen SCRs the size of coffee
cups
> that handle hundreds of volts or more and 1200 amps or more. I
haven't
> heard of that kind of power using MOS devices. There really doesn't
> seem to be a need for them when SCRs will do the job. (Or TRIACs)
>
I guess it's because Power Mosfets or IGBTs have a lower On resistance
while conducting. And reqire less plumbing to cool the stack.
Karl
Douglas W. Jones,201H MLH,3193350740,3193382879
From article <31EAAE...@ccwf.cc.utexas.edu>,
by Bruce Bostwick <li...@ccwf.cc.utexas.edu>:
> Douglas W. Jones,201H MLH,3193350740,3193382879 wrote:
>> It's worth noting that, before the advent of successful RF vacuum tubes,
>> there was a brief flurry of activity using alternators to produce RF power
>
> I believe this was for shipboard radio transmitters, ...
It may have been done on shipboard using arcane LC networks, but my source
is a 1912 Telephone Handbook, in the chapter on Radiotelephony, and the
reference is quite distinctly to voice broadcast using directly generated
RF power. The carbon button was, indeed, in series with the antenna.
Building a generator to produce RF would involve huge numbers of poles;
the general geometry of the poles would probably be quite similar to that
in very low speed synchronous motors or stepper motors, except that you'd
spin the darned thing at high speed.
I'm half-tempted to chuck a small permanent magnet stepper motor in a
dremel tool and see what I can get. Dremel tools easily attain 10,000 RPM,
and common stepper motors have 100 poles, so that ought to give me 16.66
KC! Not quite RF, but within an order of magnitude!
Doug Jones
jo...@cs.uiowa.edu
Brendan Kirby
Chris Woodrow
Brendan Kirby wrote:
>
> Hi Chris,
>
>... inductance as well as complexity lead you to prefer to use a single conductor when you can.
>
> Thanks!
>
>
Complexity yes, inductance no. The average inductance per phase is
Lx = 2 x 10^-7 x ln(Dm/Ds) where Ds is the self GMD (effective diameter
of each bundle.). Thus as the effective diameter of each bundle increases,
the inductance decreases.
Chris Woodrow
c...@ornl.gov
Brendan Kirby
Hi Chris,
Checking the venerable old Westinghouse T&D book I was surprised to find
that the Xa term (inductance from the equivalent conductor diameter) is
more significant than I had recalled. So while corona forces you to split
the phase conductor into a bundle above about 230KV inductance as well as
complexity lead you to prefer to use a single conductor when you can.
Thanks!
Chris Woodrow <c...@ornl.gov> wrote:
>> Brendan Kirby
>> Oak Ridge National Lab
>>
>> B...@ORNL.GOV
>
>It is done for both reasons. I quote from "Elements of Power Systems Analysis" ..
>"... Reduced reactance is the other equally important advantage of bundling."
>
>Chris Woodrow
>c...@ornl.gov
--
Chris Matthaei
>I'm half-tempted to chuck a small permanent magnet stepper motor in a
>dremel tool and see what I can get.
A broken stepper motor? :)
>Dremel tools easily attain 10,000 RPM,
>and common stepper motors have 100 poles, so that ought to give me 16.66
>KC! Not quite RF, but within an order of magnitude!
Wow. You just made it clear how difficult this method must have been. They
must have used 1000 pole alternators or something. I remember seeing a display
of one of these transmitters at a museum in Europe. I think it was in
Switzerland. It transmitted at around 100 KHz. I remember being amazed that
this had ever actually been done.
Chris
Chris Matthaei
prof...@cybercomm.net (Sir Spamalot) writes:
>>Charles L. Perrin wrote:
>>> Also, if you get much below 50Hz, light bulbs tend to turn into strobe
>>> lights.
...deleted...
>Then, why not 10Hz????
The answer is in the post that you followed up to! See above.
Chris
dave pierson
>The 60Hz used in America originated, I believe, with the Westinghouse Company
>and the Niagara Falls project in the 1890s.
60 was picked by Tesla, consulting for Westinghouse.
Niagara falls included substantial 25 Hz, for 'motor loads', notably
rotaries for DC for trollies and electric refining (aluminum,
carborundum).
>If I recall correctly, a previous thread in one of these
>newsgroups mentioned that Japan has or had two separate systems, one running
>on 50Hz and the other on 60Hz!
Has...
Jason Bruce
Lindsay D. Bruce j...@tx3.com
Bonneville Power has a 520,000 volt transmission system and we bundle our
overhead conductors, spaced apart by "spiders" or spreaders for several
reasons. one is to reduce corona. Another is to reduce the EMF impact at
ground level. Another is to increase ampacity due to the previous "skin
effect" mentioned(three conductors has more surface area than one large
conductor). It is also easier to standardize conductors to only a few
different sizes and string two or three or however many are needed.
> "William E. Sabin" <sab...@crpl.cedar-rapids.lib.ia.us> wrote in article
<31EABF...@crpl.cedar-rapids.lib.ia.us>...
> Douglas W. Jones,201H MLH,3193350740,3193382879 wrote:
> >
dave pierson
> Canada prior to 1950 was 25 Hertz.
> As a point of interest ASEA Electric in Sweden pioneered 500KV DC
> transmission lines. That was 10-15 years ago.
HVDC dates back to the 1900s, with some truly baroque engineering.
It revived, courtesy of mercury arc technolocgy, at a guess, from 1950
on, prinicapally in Scandavaian countries (Some of the electrons i
de-energize to send this arrive from 'ydro Quebec via tha +/- 500KVDC
link. Terminal/inverter is about 15 mi up the road...)
Marvin L. Jones
William E. Sabin (sab...@crpl.cedar-rapids.lib.ia.us) wrote:
: Chris Woodrow wrote:
: >
: > This is mainly to reduce inductance, not skin effect.
: The transposing is done to reduce radiation by virtue of field
: cancellation.
And, I believe, to reduce induced voltages from nearby lightning
strikes.
--
Marvin L Jones | in Denver: az...@freenet.uchsc.edu
Jonesy | in Gunnison: jo...@rmii.com
WB0GNO | on CompuServe: 72103,443
| via snail-mail: 81230-1371
Stephen Schiller
Well, I guess I should have made may message clearer. I agree
with you completely. What I was explain is that even though
you and I think about the skin effect, many people don't
and yet they succesfully build circuts that carry frequencies
up to, say, 1MHz. The key word in my message is "usually", as in
"it is not usually necessary to consider the skin effect".
And the reason, as I mentioned, is that it doesn't matter
much for many circuts (i.e. low power, with short wiring) if
the resistance of PC traces between components are .0001 ohms
or .1 ohms. Even a 1 ohm trace is not noticed in many circuts
where impedances are on the order of 1Kohm.
John Phillips
ea...@livenet.net (Earl Kiosterud) wrote:
>In article <31E951...@interlog.com>,
> James Brooks <jbr...@interlog.com> wrote:
>>Griff Hopkins wrote:
>>>
>>> Can anyone enlighten me on the history of 60Hz as the (U.S.)
>>> standard line frequency.
> ...
>>> Griff Hopkins
>>> Director of Engineering/
>>> Primus Technology Group
>>
>>An interesting side-note
>>
>>If you ask someone in North America where 60Hz is the norm, to hum, they
>>will hum at 60Hz or the 2nd or 3rd harmonic of 60.
>>
>>If you ask someone in Europe where 50Hz is the norm, to hum, they will
>>hum at 50Hz or the 2nd or 3rd harmonic of 50.
>>Yet another interesting use of PSYCHO-ACOUSTICS
>>Patrick Rea
>>jbr...@interlog.com
>Most devices that emit an audible hum (motors, etc) do so at twice the 60 Hz.
>frequency. So we don't really hear a second harmonic; 120 Hz. is the
>fundamental frequency being radiated. This is because each half-cycle of the
>60 Hz. wave produces one complete cycle of vibration. Removing the magnet
>from a speaker would cause the same thing to happen (to the extent the the
>speaker still worked at all!).
>FWIW.
>Earl K. Virginia Beach, VA ea...@livenet.net
Sorry, large three phase power system devices such as transformers
and reactors hum at 120 Hz due to the magnitizing current.
Regards,
John Phillips
Superintendent of Power
Niagara Power Project
New York Power Authority
work e-mail phil...@ip3gate.usa.com
John Brooks
In article <4sh9kf$q...@cc.iu.net>, jim <jma...@iu.net> writes
>jo...@pyrite.cs.uiowa.edu (Douglas W. Jones,201H
>>Building a generator to produce RF would involve huge numbers of poles;
> low ... down in the 150khz region. This would make it far
> easier to build an RF alternator. Also, some people used
> to start with DC and use a large, light, rotor with
> contacts lining the edge. It was easier to spin-up this
> disk than to try and combine both generated power and
> high freqs into one machine.
whaddya mean 'maritime' ...'still are'
good old BBC Radio 4 still goes out over UK at 198KHz.
Also carries radio teleswitch broadcast for utility use (which neatly
get's us back onto (a different) topic :=) )
>
>
<snip some further experimental ideas which sound very noisy (in the
radio spectrum)>
Hey Jim, I hope you've got tolerant (or no) neighbours!
--
John Brooks
Walter Gray
In article <4sgcr5$m...@flood.weeg.uiowa.edu>, jo...@pyrite.cs.uiowa.edu (Douglas W. Jones,201H MLH,3193350740,3193382879) writes:
>From article <31EAAE...@ccwf.cc.utexas.edu>,
>by Bruce Bostwick <li...@ccwf.cc.utexas.edu>:
>>> there was a brief flurry of activity using alternators to produce RF power
>>> directly for broadcast AM radio. ...
>>
>> I believe this was for shipboard radio transmitters, ...
>
>It may have been done on shipboard using arcane LC networks, but my source
>is a 1912 Telephone Handbook, in the chapter on Radiotelephony, and the
>reference is quite distinctly to voice broadcast using directly generated
>RF power. The carbon button was, indeed, in series with the antenna.
>
>in very low speed synchronous motors or stepper motors, except that you'd
>spin the darned thing at high speed.
>
>and common stepper motors have 100 poles, so that ought to give me 16.66
>KC! Not quite RF, but within an order of magnitude!
>
I saw one of these RF alternators in a museum years ago. It's just like
any alternator except there are *hundreds* of poles. I think only the
Germans went in for them in a big way. They enjoy a bit of high precision
engineering.
Walter
------
Walter Gray
In article <4satpq$1...@news01.deltanet.com>, jlun...@delta1.deltanet.com (John Lundgren) writes:
>Griff Hopkins (75561...@CompuServe.COM) wrote:
>: Can anyone enlighten me on the history of 60Hz as the (U.S.)
>: countries!?!?
>
>: which to transfer power. Aviation electronics has been using
>: 400Hz for as long as I remember. At 400Hz, transformers and power
>: supply filters are significantly smaller. Also, EMF (low freq.
>
>wasn't the problem.
>
>But it is significantly harder to get a big generator to spin 7 times
>faster to get 400 Hz. It would probably fly apart. Remember that these
>are giant generators inside dams and in steam plants, and they are not
>concerned about weight.
>
>And the BIG problem is that it is significantly *harder* to filter out
>400 Hz from audio amps or whatever. That's right in the middle of the
>audio passband.
>
>As for low frequency health problems, they are _already_ diminished.
>
>After working on RADARS in the army, I would never want to go back to
>listening to that constant irritating WHINE of 400 Hz blowers.
I used to work with a radar that used a lot of 1660 Hz servos. Try that
anytime you want a *real* headache.
Walter
------
Walter Gray
In article <4sdjia$u...@flood.weeg.uiowa.edu>, jo...@pyrite.cs.uiowa.edu (Douglas W. Jones,201H MLH,3193350740,3193382879) writes:
>From article <31e97361...@news.dial.pipex.com>,
>by ft...@dial.pipex.com (Peter):
>
>> To get 50Hz, you make a two-pole generator (not possible to have fewer
>> poles than 2) and run it at 3000 RPM. For 60Hz, you run it at 3600 RPM
>> which is better.
>
>> Generating much higher frequencies is easy, e.g. a 20-pole generator
>> running at 3000 RPM would give you 500Hz.
>
>It's worth noting that, before the advent of successful RF vacuum tubes,
>there was a brief flurry of activity using alternators to produce RF power
>by running the audio signal through the alternator's field windings.
>That would mean that your entire circuit for an AM broadcast transmitter
>would consist of a battery, carbon button microphone and alternator field
>winding in series, with the output of the alternator wired directly to the
>antenna.
Could be wrong but I thought alternators (at about 40 kHz) were only
used for Morse code, eg Telefunken before WW1.
Walter
------
Mr. Brooke Clarke
Griff Hopkins wrote:
>
> Can anyone enlighten me on the history of 60Hz as the (U.S.)
It is my understanding that when Tesla invented the A.C. power system he choose
60 cycles per second (now called Hertz) in order to minimize the cost of motors
and generators. This is a compromise based on the relative cost of copper (for wire)
and steel (for laminations). Tesla's agreement with Geroge Westinghouse was that
Tesla would be paid $1.00 per horsepower. Later at Geroges verbal request Tesla
released Westinghouse from it's contract!
Have Fun,
Brooke
dave pierson
My reading indicates that the hollow (and, later, bundled) conductors are
entirely for corona purposes. A lot of work went into corona reduction as the
voltages climbed. Bundled is clearly for corona, as the skin effect would
apply to each of the elements of the bundle...
Transpositions (usual name for 'twisting') makes a better balance (which
reduces 'radiation'). also coupling to phone lines and balance for protective
relaying...
Robert Moore
Mike658 wrote:
> Aircraft power probably uses 400 hz as a result of the high source
> (turbine) frequencies. It is probably a compromise designed to reduce
> losses involved in coming all the way down to 60 hz.
Nope!
It's simply a matter of weight and size.
Same reason we use 24v. DC.
Bob Moore
Airline Transport Pilot B-707 B727
Flight Engineer-- Turbine
dave pierson
In article <31EAAE...@ccwf.cc.utexas.edu>, Bruce Bostwick
<li...@ccwf.cc.utexas.edu> writes...
>I believe this was for shipboard radio transmitters,
Land based, actually. They ran HUGE.
(I have some vintage, original GE paperwork on them....)
>and the alternator didn't generate the RF.
They did. Ther were a coupel of different schemes, reflector and
direct. Direct was just that, very trick technciques generated rf (at
LF) direct.
>The RF was generated by an arcane LC network powered by the alternator,
This might be a description of the reflection technique. A fundamental,
say at 10,000 Hz (i could look up numbers) ws generated. This was
run into a an INTENTIONALLY saturated magnetic core, hence, harmonics.
THIS was LC filtered and fed BACK as excitation to the alternator,
which loyally multipled it up. A couple of stages of this led to
100s of KHz. Look for names like Fessende and Alexanderson.
>It only worked for code, of course (this was in the *early* days,>folks!)
Fessenden was transmitting voice.
It was CW. Some modulated direct, using multiple carbon buttons, water
cooled, as noted earlier. Some modulated the intial DC field, using the
alternator as mechanical amplifier.
>They did actually have 'phone transmitters back then, but they used *RELAYS*,
One needs a certain amount of care, here, since the word 'relay'
existed, and described the function of amplification for land line CODE,
the same word was used to describe an AMPLIFIER, built around an
electromagnetically controlled carbon buttom. [Little known fact
(these days... 8)>>) a carbon button element IS an amplifier. More
DC/AC energy variation out is available than mechanical
(acoustic/pneumatic) energy applied.) Telco built an initial set
of long line amps based on this.
>believe it or not, to modulate the RF.
I suspect that these were straight carbon button, as above.
>These were cantankerous and unreliable instruments to say the least ..
indeed.
>I've also heard that some of the early audion detectors used a Bunsen burner
>flame instead of a vacuum ...
deForest never really understood his audion. He believed that SOME
gas was necessary for operation. GE, for one, developed 'the real
McCoy', with high vaccuum (as did a whole host of others.
There are pages of various detectors in vintage Wireless books
(yep, got those too) and the flame detector sounds familiar.
William E. Sabin
Dave Turner wrote:
>
> I grew up in Boulder City, Nevada (6 miles from Hoover Dam).
> My father worked for The City of Los Angeles, Department of Water and
> Power which contracted for most of the power produced by Hoover Dam.
>
> The powerlines between Hoover Dam and Los Angeles were hollow copper.
> I was told by several of the engineers that they were hollow because
> of the skin effect. The saving in copper and weight were substantial.
>
> Each cable was about 1.5 inches in diameter; the outer "shell" was
> less than 1/8 inch thick. The core was air.
>
> The main towers used three such cables (one per phase) with two ground
> wires above. There is (was) a copper counterpoise buried beneath the
> transmission lines. (People used to dig up the counterpoise in order
> to sell the copper.)
>
> The construction of the cable was interesting.
>
> In order to be flexible, the shell was made from a number of flat strips
> of copper; each strip was about 1/2 inch wide. One edge had a small
> tongue and the other had a small groove. (It looked like a small
> tongue and groove board.) The flat strips were connected together
> using the tongues and grooves joined together to make a circular cable.
> The strips were not straight along the length of the cable
> but spiraled along the length with a twist of about one turn every
> couple of feet.
>
> We used to find lots of it underneath the powerlines near Boulder City.
>
> My parents still in BC. I vaguely remember my father saying that the copper
> has been replaced by aluminum, but I can't verify that.
>
Very interesting. Thanks.
Bill
John Phillips
Chris Woodrow <c...@ornl.gov> wrote:
>Douglas W. Jones,201H MLH,3193350740,3193382879 wrote:
>>
>> From article <31EA7A...@crpl.cedar-rapids.lib.ia.us>,
>> by "William E. Sabin" <sab...@crpl.cedar-rapids.lib.ia.us>:
>> >
>> > On long, high current transmission lines, skin effect is very important,
>> > even at 60 Hz. It's my understanding that a *hollow* conductor with a
>> > nonconducting core is sometimes used in power transmission, partly also
>> > to help reduce corona effects. Does anyone know something about that?
>>
>> More often, they solve the skin effect problem with a group of conductors.
>> Many high-tension lines have bundles of 3 or 4 conductors, spaced about
>> a foot apart and held apart by "spiders" to make each "wire". A single
>> insulator suspends the bundle from each tower.
>This is mainly to reduce inductance, not skin effect.
While this may be an effect, the main reason for bundlling is to
reduce corona.
>>
>> Another classic reaction to the skin effect problem is to use copper
>> clad steel wire. The low resistance metal is used only for the skin,
>> while the high tensile strength metal is used for the body, thus allowing
>> a longer inter-tower spacing. Do they do this with aluminum too?
>The most common is ACSR (Aluminum conductor steel reinforced). With steel
>stranding on the inside and aluminum stranding on the outside. The main
>purpose of the steel is to provide strength for longer spans.
>>
>> But, another problem with high frequency long-distance transmission is
>> radiative loss. At 60 cycles this is a problem; they solve it by
>> "twisting" the transmission line (we use the same trick with twisted pair
>> wires, on a smaller scale). Twists in high-tension lines are not done
>> continuously; instead, every few miles, there's a special tower or tower
>> pair that rotates the wires. For a 3-wire line where all 3 are normally
>> carried horizontally (left, center, right), the right line might dive
>> down to the bottom position on the "twist" tower, then come up on the
>> left while the center wire shifts to the right and the right wire shifts
>> to the center.
>>
>I don't think tranposition reduces inductance much, it just makes it even
>across all three phases so that the voltages are in balance.
Yes, it makes each phase impedance the same and is usually
accomplished at 1/3 increments of the line. It also is accomplished to
match phases,
>> The spacing between these twist points depends on the wavelength. The
>> higher the frequency, the more frequently you need to twist the line in
>> order to prevent radiation. Each twist costs money -- special towers and
>> a break in the easy "straight line" wire stringing process.
>>
>> Doug Jones
>> jo...@cs.uiowa.edu
>Is this going in the Guinness Book of Records as the worlds longest thread?
>If so, I wanted to be included.
>Chris Woodrow
John Phillips
jlun...@delta1.deltanet.com (John Lundgren) wrote:
>Griff Hopkins (75561...@CompuServe.COM) wrote:
>: Can anyone enlighten me on the history of 60Hz as the (U.S.)
>: standard line frequency. I seem to remember being taught that
>: 60Hz came about as a result of electric clocks (i.e.- the clocks
>: needed 60 cycles). While this makes sense (to ignorant me), it
>: certainly doesn't explain the use of 50Hz standards used by other
>: countries!?!?
>: It would appear that 60Hz isn't the most efficient frequency at
>: which to transfer power. Aviation electronics has been using
>: 400Hz for as long as I remember. At 400Hz, transformers and power
>: supply filters are significantly smaller. Also, EMF (low freq.
>: health) problems would seem to be greatly dimenished.
>Actually the transformers, etc, are significantly lighter. The size
>wasn't the problem.
>But it is significantly harder to get a big generator to spin 7 times
>faster to get 400 Hz. It would probably fly apart. Remember that these
>are giant generators inside dams and in steam plants, and they are not
>concerned about weight.
No, you increase the number of rotor poles.
>And the BIG problem is that it is significantly *harder* to filter out
>400 Hz from audio amps or whatever. That's right in the middle of the
>audio passband.
>As for low frequency health problems, they are _already_ diminished.
>After working on RADARS in the army, I would never want to go back to
>listening to that constant irritating WHINE of 400 Hz blowers.
>: I would appreciate any enlightenment on the history, use, and
>: possible future trends for A.C. Power transfer. Thank you for
>: your time.
>: Griff Hopkins
>: Director of Engineering/
>: Primus Technology Group
>--
>#======P=G=P==k=e=y==a=v=a=i=l=a=b=l=e==u=p=o=n==r=e=q=u=e=s=t======#
>| John Lundgren - Elec Tech - Info Tech Svcs. | jlundgre@ |
>| Rancho Santiago Community College District | deltanet.com |
>| 17th St at Bristol \ Santa Ana, CA 92706 | http://www.rancho|
>| My opinions are my own, and not my employer's. | .cc.ca.us |
>| Most FAQs are available through Thomas Fine's WWW FAQ archive: |
>|http://www.cis.ohio-state.edu:80/hypertext/faq/usenet/FAQ-List.html|
>| "You can flame your brains out -- it won't take long." |
>#===T=u=z=l=a==C=o=m=p=a=n=y=.=.===t=h=r=e=e='=s==L=e==C=r=o=w=d=!==#
jim
jo...@pyrite.cs.uiowa.edu (Douglas W. Jones,201H
>Building a generator to produce RF would involve huge numbers of poles;
>the general geometry of the poles would probably be quite similar to that
>in very low speed synchronous motors or stepper motors, except that you'd
>spin the darned thing at high speed.
>I'm half-tempted to chuck a small permanent magnet stepper motor in a
>dremel tool and see what I can get. Dremel tools easily attain 10,000 RPM,
>and common stepper motors have 100 poles, so that ought to give me 16.66
>KC! Not quite RF, but within an order of magnitude!
Of note - maritime frequencies were (some still are) very
low ... down in the 150khz region. This would make it far
easier to build an RF alternator. Also, some people used
to start with DC and use a large, light, rotor with
contacts lining the edge. It was easier to spin-up this
disk than to try and combine both generated power and
high freqs into one machine.
Try making a rotor out of the thin fiberglas printed circuit
board material - you can etch in the conductors. Make it
about 2.5 " in diameter and then carefully turn the edge
down in a lathe to achieve as perfect a uniformity as
possible. Dremel tools commonly reach 15,000+ rpm these
days and the disk has to be well balanced or it will
self destruct. Then all you need are some brushes and
a large capacitor. Touch one brush near the edge of
the disk and put the other on the chuck of the Dremel
tools' chuck. Feed it DC. The output should go through
the big cap - making a rough plus/minus sine wave.
Now, if you had a 2" disk with contacts spaced at 1/10"
intervals rotating at 15,000 rpm ... that's about
a 6.28" circumference giving us about 63 contact points
around that circumference times 15k = 945 KHz ... smack
in the middle of the AM broadcast band. By plating the
contacts and adding anti-spark caps and you could
probably sustain a 25 watt throughput just using this
little disk. Now imagine a carbon-fibre/epoxy disk a
couple of feet in diameter spinning in a vaccuum at
maybe 50,000 rpm. Easy to hit several MHz and hundreds
of watts - esp if you crank up the voltage as high as
possible. Then you can be creative by using multiple
non-linearly-spaced brushes.
You can also use photo-cells and a slotted disk - try
a polyester based photo film such as Tech-Pan and
just image the light/dark pattern onto it. You can
spin it up to really high speeds. The old-style
cesium-metal photocells should offer a fairly
high response frequency.
--jim
James Brooks
John Phillips wrote:
> >>If you ask someone in North America where 60Hz is the norm, to hum, they
> >>will hum at 60Hz or the 2nd or 3rd harmonic of 60.
> >>
> >>If you ask someone in Europe where 50Hz is the norm, to hum, they will
> >>hum at 50Hz or the 2nd or 3rd harmonic of 50.
> >>Yet another interesting use of PSYCHO-ACOUSTICS
> >>Patrick Rea
> >>jbr...@interlog.com
>
> >Most devices that emit an audible hum (motors, etc) do so at twice the 60 Hz.
> >frequency. So we don't really hear a second harmonic; 120 Hz. is the
> >fundamental frequency being radiated. This is because each half-cycle of the
> >60 Hz. wave produces one complete cycle of vibration. Removing the magnet
> >from a speaker would cause the same thing to happen (to the extent the the
> >speaker still worked at all!).
>
> >FWIW.
>
> >Earl K. Virginia Beach, VA ea...@livenet.net
>
> Sorry, large three phase power system devices such as transformers
> and reactors hum at 120 Hz due to the magnitizing current.
I stand corrected. But you must agree taht it is true.
Patrick Rea
Crisis Digital Productions
jbr...@interlog.com
Pin 2 hot
I think you're confusing RPM (revolutions per minute) with
RPS (revolutions per second). It is not going to be as easy
as this...check your math. 15,000rpM = 250rpS.
William E. Sabin
Stephen Schiller wrote:
> Well, I guess I should have made may message clearer. I agree
> with you completely. What I was explain is that even though
> you and I think about the skin effect, many people don't
> and yet they succesfully build circuts that carry frequencies
> up to, say, 1MHz. The key word in my message is "usually", as in
> "it is not usually necessary to consider the skin effect".
> And the reason, as I mentioned, is that it doesn't matter
> much for many circuts (i.e. low power, with short wiring) if
> the resistance of PC traces between components are .0001 ohms
> or .1 ohms. Even a 1 ohm trace is not noticed in many circuts
> where impedances are on the order of 1Kohm.
Yes, that is right. Where low frequency skin effect is important is in
coils and transformers of one kind or another. Also, in this thread we
have learned that power company folks think about skin effect on long
lines and also about the phenomenon that is *responsible* for skin
effect, the wire's "internal inductance".
Bill W0IYH
Chris Matthaei
jma...@iu.net (jim) writes:
...snip...
> Now, if you had a 2" disk with contacts spaced at 1/10"
> intervals rotating at 15,000 rpm ... that's about
> a 6.28" circumference giving us about 63 contact points
> around that circumference times 15k = 945 KHz ... smack
> in the middle of the AM broadcast band. By plating the
Nope. 15000 RPM = 250 RPS. You'd only get 15.75 KHz out of this setup. You
need ALOT of contacts to get a useful (but still low) frequency. That's why
nobody uses this method any more. :)
Chris
Dave Turner
In article <31EA7A...@crpl.cedar-rapids.lib.ia.us> "William E. Sabin" <sab...@crpl.cedar-rapids.lib.ia.us> writes:
>
>On long, high current transmission lines, skin effect is very important,
>even at 60 Hz. It's my understanding that a *hollow* conductor with a
>nonconducting core is sometimes used in power transmission, partly also
>to help reduce corona effects. Does anyone know something about that?
>
I grew up in Boulder City, Nevada (6 miles from Hoover Dam).
A couple of miles south of BC is one of the Pacific InterTie stations
where the AC is converted to DC.
All of my reference books on Hoover Dam are in storage so I can't be
more exact.
--
Dave Turner (510) 823-2001 dmt...@pacbell.com
James Brooks
John Lundgren wrote:
> : An interesting side-note
>
> : If you ask someone in North America where 60Hz is the norm, to hum, they
> : will hum at 60Hz or the 2nd or 3rd harmonic of 60.
>
> : If you ask someone in Europe where 50Hz is the norm, to hum, they will
> : hum at 50Hz or the 2nd or 3rd harmonic of 50.
>
> : Yet another interesting use of PSYCHO-ACOUSTICS
>
> could say this in general. It might apply to those who do, tho.
>
> : Patrick Rea
> : Crisis Digital Productions
> : jbr...@interlog.com
It isn't so much a matter of perfect pitch. The tones are so engrined
into our being (from childbirth) that we do it unconsiously. Everything
around us radiates tones. Be it your "noisy" incandescent bulb or the fan
cooling you on a summer's night. Even the power lines running through
the walls of your house emit these tones. The only real exceptions are
the fluorescent and neon lamps.
If you listen closely you can hear it. Better yet, take a very accurate
audio measurement system (Ivie at the very least) and measure the AF
spectrum.
Jud Williams
In <31EBC0...@ibm.net> Mike658 <mik...@ibm.net> writes:
>Griff Hopkins wrote:
>>
>> Can anyone enlighten me on the history of 60Hz as the (U.S.)
>> standard line frequency. I seem to remember being taught that
>> 60Hz came about as a result of electric clocks (i.e.- the clocks
>> needed 60 cycles). While this makes sense (to ignorant me), it
>> certainly doesn't explain the use of 50Hz standards used by other
>> countries!?!?
>>
>> It would appear that 60Hz isn't the most efficient frequency at
>> which to transfer power. Aviation electronics has been using
>> 400Hz for as long as I remember. At 400Hz, transformers and power
>> supply filters are significantly smaller. Also, EMF (low freq.
>> health) problems would seem to be greatly dimenished.
>>
>> possible future trends for A.C. Power transfer. Thank you for
>> your time.
>>
>> Griff Hopkins
>> Director of Engineering/
>> Primus Technology Group
>
own, I
>think the best explanation for the 60hz decision was the one about
>originally using 50hz and then having to crank it up to get a little
more
>power.
>
>While they do exits, skin losses and radiative losses are not
>substantial at power line frequencies.
>
>Aircraft power probably uses 400 hz as a result of the high source
>(turbine) frequencies. It is probably a compromise designed to reduce
>losses involved in coming all the way down to 60 hz.
>
>
>Michael Gaithersburg. Maryland
>(mik...@ibm.net)
>(micha...@worldnet.att.net)
I would guess that aircraft use 400Hz because the components are much
lighter and the plane would not be burdened with excessive weight.
Regards,
Jud Wiliams
Philip Caskey, PE
(snip)
> --->>
> --->> Also, if you get much below 50Hz, light bulbs tend to turn
> into strobe
> --->> lights.
> --->>
> --->>
> --->
> --->The resistance of a power transmission line wire at 400 Hz is
> 2.58 times
> --->the resistance at 60 Hz due to skin effect (square root of
> frequency).
> --->
> --->Bill W0IYH
>
> Then, why not 10Hz????
>
>
Like the man said, below 50Hz lights flicker noticably.
--
Philip Caskey, PE
mor...@bright.net
Any opinions expressed above are my own and no other's;
however, should you choose to agree with them, you are indeed
a wise and sophisticated individual.
jim
fu...@MCS.COM (Chris Matthaei) wrote:
>jma...@iu.net (jim) writes:
>...snip...
Oops ! Off by a factor of 60 ! Oh well ...
Yes, one would need a lot of contacts and there are
obviously limitations on how fast one can spin a
disk of x-size made of material 'y'. Hmmm ... now
if you used multiple disks staggered slightly out
of phase from each other, you might be able to
generate a higher composite frequency ... ? There
may be a few mechanical tricks availible.
On the other hand, in the VERY early radio days, they
used VERY low frequencies - being all the hardware
could cope with. Marconi built some HUGE antennas -
and they weren't even full-wave.
--jim
John Graley
In article <VA.0000001...@karlq.io.org>, Karl Quies
<ka...@io.org> writes
>>
>> Remember that an inductor does not have any losses (ideally).
>>
> Correct. But it changes the powerfactor of the system.
> and all that useless current circulating out of Phase through the
> 'ideal' inductor creates resistive losses in the 1000 miles of wire
> used.
You can aleviate this problem using reactive compensators spaced along
the line.
--
John Graley, jo...@hugebass.demon.co.uk
2 Belvedere Villas, Lansdown Road, Home: (+44) (01225) 466530
Bath, Somerset, England BA1 5HS Work: (+44) (01225) 444888
Bill Putney
Mr. Brooke Clarke wrote:
> > Griff Hopkins wrote:
> >
> > Can anyone enlighten me on the history of 60Hz as the (U.S.)
>
> It is my understanding that when Tesla invented the A.C. power system he choose
> 60 cycles per second (now called Hertz) in order to minimize the cost of motors
> and generators. This is a compromise based on the relative cost of copper (for wire)
> and steel (for laminations). Tesla's agreement with Geroge Westinghouse was that
> Tesla would be paid $1.00 per horsepower. Later at Geroges verbal request Tesla
> released Westinghouse from it's contract!
>
> Have Fun,
> Brooke
While it is true that the first commercial AC power generating stations were built by
Tesla/Westinghouse, the first few of these generating stations installed at Niagara
Falls produced 20 Hz power. This was probabily (but I don't know it for sure) to reduce
the speed of the very large rotaing parts for a high power generator. Until fairly
recently an aluminum reduction plant was still using the 20 Hz power from one of the old
stations.
- Bill
--
=====================================================================
# Bill Putney - Ph: [415-33]6-5122 | Sun Microsystems, Inc #
# Email: bill....@eng.sun.com | 2550 Garcia Ave. MS: PAL1-224 #
# WB6RFW - 443.400 Mhz, 100 Hz | Mountain View, CA 94043-1100 #
=====================================================================
Thomas Prufer
jo...@pyrite.cs.uiowa.edu (Douglas W. Jones,201H
MLH,3193350740,3193382879) wrote:
(...)
>So, the frequency we use is a compromize. 60 Hz is common in the
>Americas, 50 Hz in Europe, and railroad electrification has used frequencies
>as low as 18 Hz (20 Hz was once common). Railroads find motor efficiency
>to be of primary concern -- the eddy current losses at 60 Hz were once
>seen as too much, and adding to the engine weight with a big transformer
>only reduces the amount of ballast they need to add in order to avoid
>slipping.
(...)
And the railroad still uses 16 2/3 Hz in Germany, at least.
Tom
marc_k
Bill Putney (bill....@eng.sun.com) wrote:
: - Bill
In NYC, parts of the subway system still use 25 cy power for the station
lighting(and yes, the flicker is *very* noticable).
Bob Sullivan
In article <Pine.OSF.3.91.96071...@ucs.orst.edu>,
e <pee...@ucs.orst.edu> wrote:
->
->I wonder whether the power companies have a better idea of why they do the
->things they do concerning power distribution than those involved in this
->"history" thread. Funny that for something apparently well understood (I
->say this as someone still learning E&M basics) there can be so many
->differing ideas and necessary clarifications; I guess that is why I like
->science.
->
->Travis...
I can see you have never spent any time on the sci.* newsgroups, if you think the
The History of 60Hz A.C.? thread is full of "differing ideas and necessary
clarifications."
Go to sci.physics and make any definite statement about General Relativity or
quantum reality and wait for the vultures to descend. It will make you wonder
why it is that the power companies have a much better understanding of the whys
and wherefores of powerline frequencies than the scientists have of mainstream
science.
John Lundgren
Thomas Prufer (10136...@compuserve.com) wrote:
: jo...@pyrite.cs.uiowa.edu (Douglas W. Jones,201H
: Tom
When I was stationed in Germany in the army, I had to get used to the
railroad. We were in a barracks across the street from a railroad yard.
The yard was filled with tracks each having a high tension wire above it
for power. The trains would spark and at night the flashes could be seen
on the ceiling when the lights were out. But when a long train was
leaving, the train usually had to have a steam engine to assist since
the power needed was too much for the electrical lines. So they had to
have some steam engines around. The diesel engines weren't as popular, I
guess because they cost a lot more and the fuel was a lot more expensive.
I never knew what the RR was being run on. Our 'generator' at the
missile site was working on about 1.3 GHz, better known as a RADAR. It
used power from the 50 Hz commercial supply, but we kept a couple 100 KW
diesel generators running as backup.
--
#===================================================================#
| John Lundgren - Elec Tech - Info Tech Svcs. | jlundgre@ |
| Rancho Santiago Community College District | deltanet.com |
| 17th St at Bristol \ Santa Ana, CA 92706 | http://www.rancho|
| My opinions are my own, and not my employer's. | .cc.ca.us |
| Most FAQs are available through Thomas Fine's WWW FAQ archive: |
|http://www.cis.ohio-state.edu:80/hypertext/faq/usenet/FAQ-List.html|
| "Babe Ruth struck out 1,330 times... keep on swinging." |
| says the lid on the jar of Laredo & Lefty's Picante Salsa |
#======P=G=P==k=e=y==a=v=a=i=l=a=b=l=e==u=p=o=n==r=e=q=u=e=s=t======#
Jud Williams
Alanfoley
This is a great thread. When Tesla and Westinghouse made their deal Edison
was in concerted opposition to them (Tesla actually conceived AC whilst
musing on a Faust verse in Vienna). The electric motors of that day were
big central plant motors for central power plants in factories and trains
etc., this had a profound effect on the choice of frequencies. It wasn't
until the 1920's that small electric motors, analogous to todays PC's,
replaced the central plant motors, analogous to the mainframe computers of
the sixties and seventies.
Source: "The Engines of Our Ingenuity" Episode #503, http://www.uh.edu
Engines is a radio show authored and read by Dr. John Lienhard at the
University of Houston, TX. He has many episodes which cover issues in the
development of electricity, one is the source of the above. Episode #179,
The Electric Chair is posted at
http://users.aol.com/powerclear/engines.html on the Texas Electricity
Homepage for browsers, but I encourage you all to listen to the radio
show.
alan...@aol.com
RateCheckers Utility Consultants
Houston, Tx
John Graley
In article <4sj8p5$m...@Mercury.mcs.com>, Chris Matthaei <fu...@MCS.COM>
writes
>jma...@iu.net (jim) writes:
>
>...snip...
>
>> Now, if you had a 2" disk with contacts spaced at 1/10"
>> intervals rotating at 15,000 rpm ... that's about
>> a 6.28" circumference giving us about 63 contact points
>> around that circumference times 15k = 945 KHz ... smack
>> in the middle of the AM broadcast band. By plating the
>
>Nope. 15000 RPM = 250 RPS. You'd only get 15.75 KHz out of this setup. You
>need ALOT of contacts to get a useful (but still low) frequency. That's why
>nobody uses this method any more. :)
Wouldn't this system produce a square (or rectangular) wave? If so, it
could be filtered for a harmonic using capacitors and inductors, which
are easy to make...
>Chris
>
Cheers, John
Steve Work
Jud Williams (ju...@ix.netcom.com) wrote:
: What is a reactive compensator?
A big capacitor. Attached to powerlines to improve the power factor,
since loads are generally inductive.
Ed Pearlstein
bsul...@sky.net (Bob Sullivan) writes, in part:
>Go to sci.physics and make any definite statement about General Relativity or
>quantum reality and wait for the vultures to descend. It will make you wonder
>why it is that the power companies have a much better understanding of the whys
>and wherefores of powerline frequencies than the scientists have of mainstream
>science.
The reason why is that the mainstream fields that scientists study are
those fields which are not well understood. That's what scientific research
is all about! When something becomes well-understood, such as the basics of
electricity, its further development passes from the scientists to the
engineers.
Ron Schmitt
My two cents on this never ending thread:
The wavelength of 60Hz is 5e6 meters or about 3100 miles. So I would
figure that for any power transmission lines running a couple of hundred
miles or more, radiation would have to be considered. I also figure that
the power from large power plants is transmitted to regions that are
hundreds of miles away. Any comments?
--
Ron Schmitt
rsch...@nortel.ca
Nortel / Northern Telecom
* Opinions expressed are my own and not Nortel's. *
Steven F Kraus
I was under the impression that 60 Hz was chosen primarily to be
different from Europe and thus lessen foreign competition for equipment.
Of U.S. railroads using high voltage AC electrification as opposed to DC,
virtually all of it was done with 25 Hz (usually at 11 kV) except for that
installed after perhaps 1960, as many of them used locomotives with brush
type traction motors so a lower frequency was desirable. Even so, a number
of them used engines containing giant motor-generators so the more desirable
DC traction motors could be used while still getting the efficiency of HV
distribution. 25 Hz was generated either in RR-owned power plants or with
rotary converters from utility power.
Many of the U.S. electrifications were terminal districts (due to smoke
ordinances) and tunnels and these were generally dismantled after the
coming of diesels. The Milwaukee Road's 3000VDC system (that's
considered high voltage for DC) shut down in the early seventies. The
Pennsylvania & New Haven railroad's Northeast Corridor is the remaining
major electrification in the U.S. (and is being extended to Boston) and
is now owned by Amtrak and certain commuter agencies. It was 25 Hz.
There was a plan to convert it to 60 Hz and some segments were done. But
I think the plan now is to leave the 25 Hz segments as is
though with static (electronic) frequency convertors.
As has been mentioned, some of the European electrification is at 16 2/3 Hz.
It sounds like an odd number but it isn't really: It's 1000 RPM on a
2-pole generator, 500 RPM with 4 poles, 250 RPM with 8 poles.
Dean Chesterman
Nope, Radiation is not a problem, but standing wave effects are.
A transmission line at 240 kV that is about a 100 miles long could
see 300 kV at the other open end. It makes it tough to energize
equipment.
Other issues are stability with the charging current, and line
capacitance.
One neat effect was a long 144 kV line energized at 25 kV. There
was a load of 6 to 8 Megawatts on the end. The line ran with a
leading power factor due to line charging until the load exceeded
11 Megawatts then it reached unity. It played hell with a motor
starter as a big drive tried to start. The var meter on that line
was a scary thing to watch!
--
Dean Chesterman
===================================
Engineering Resources, Transmission
Phone 420 - 8078; Fax 420 - 8017
E-Mail de...@er.apl.cul.ca
" if it was easy,
it would have been done already "
===================================
Harry H Conover
Ron Schmitt <rsch...@nortel.ca> wrote:
: >My two cents on this never ending thread:
: >
: >The wavelength of 60Hz is 5e6 meters or about 3100 miles. So I would
: >figure that for any power transmission lines running a couple of hundred
: >miles or more, radiation would have to be considered. I also figure that
: >the power from large power plants is transmitted to regions that are
: >hundreds of miles away. Any comments?
I've heard these lines are paired and reversed at regular intervals.
It's supposed to be an equivalent to the use of twisted pair in telecom
to reduce radiation and coupling.
Harry C.
Woody Brison
My $.02 on this:
Experimenters with AC found that slower frequencies
caused street lights to flicker... effect gone at
or a little below 60 Hz. Same experiments in Europe
arrived at 50 Hz as the optimum. Difference was that
the Americans had a different idea of what was a
well-lit street.
John Phillips
Dean Chesterman <de...@er.apl.cul.ca> wrote:
>Ron Schmitt <rsch...@nortel.ca> wrote:
>>My two cents on this never ending thread:
>>
>>The wavelength of 60Hz is 5e6 meters or about 3100 miles. So I would
>>figure that for any power transmission lines running a couple of hundred
>>miles or more, radiation would have to be considered. I also figure that
>>the power from large power plants is transmitted to regions that are
>>hundreds of miles away. Any comments?
>>
>>--
>>
>>Ron Schmitt
>>rsch...@nortel.ca
>>Nortel / Northern Telecom
>>
>>* Opinions expressed are my own and not Nortel's. *
>Nope, Radiation is not a problem, but standing wave effects are.
>A transmission line at 240 kV that is about a 100 miles long could
>see 300 kV at the other open end. It makes it tough to energize
>equipment.
>Other issues are stability with the charging current, and line
>capacitance.
>One neat effect was a long 144 kV line energized at 25 kV. There
>was a load of 6 to 8 Megawatts on the end. The line ran with a
>leading power factor due to line charging until the load exceeded
>11 Megawatts then it reached unity. It played hell with a motor
>starter as a big drive tried to start. The var meter on that line
>was a scary thing to watch!
That's why we use reactors (switched inductive load) in substations.
>--
>Dean Chesterman
>===================================
>Engineering Resources, Transmission
>Phone 420 - 8078; Fax 420 - 8017
>E-Mail de...@er.apl.cul.ca
>" if it was easy,
>it would have been done already "
>===================================
Regards,
John Phillips
Superintendent of Power
Niagara Power Project
New York Power Authority
work e-mail phil...@ip3gate.usa.com