Small grid-tie inverters?
Maury Markowitz
I want to start with a simple two-panel install to test them head-to-
head. Since there are only two panels, even the series voltage will be
quite low. All of the inverters I've seen want high input voltages
(and it appears higher voltages are more efficient?).
So can anyone recommend an inverter useful for a single 18 VDC panel?
Is there such a thing?
Maury
bea...@gmail.com
What do you want to test? That panels make electricity? They do. That
an inverter will turn ELV into HV? They do.
You are in the process of playing with Solar Power.
Get real. Learn to correctly size and design a system to meet your
loads. Then you can start with the hardware.
z
4737-a84d-e...@27g2000hsf.googlegroups.com:
I kind of doubt it.
For tying to the grid you'll need to talk to your power company. They'll
probably have a list of approved inverters and they'll have to do some
wiring for you. I don't think they'll want to bother with such a small
system. Just charge a battery and do your testing that way ?? Then any
cheap inverter can run from a common 12 volt deep cell or whatnot
Roland Mösl
news:a271501a-6cac-4737...@27g2000hsf.googlegroups.com...
Dorfmüller is specialised in small inverters
http://live.pege.org/2005-intersolar/inverter.htm
--
Roland Mösl
http://car.pege.org cars and traffic
http://live.pege.org building and live
http://www.pege.org
Mauried
Smallest Ive seen is around 700 Watts, but still needs at least 140 V
input, and they arnt cheap, around $1100 for the 700 watt version.
There is simply no market for very small Grid Tie Inverters.
Eeyore
Maury Markowitz wrote:
> I'm in the process of starting my first PV install
Dare one ask why ?
Graham
Eeyore
Mauried wrote:
> There is simply no market for very small Grid Tie Inverters.
Because they are no practical use to man nor beast.
Graham
BobG
Florida guys like me got real tired of getting up every two hours to
put another gallon of gas in the generator back during the '04
hurricanes. I have a small pv system with some panels, a
SolarConverters MPPT charge controller, a couple of T105s and an
inverter that will run the fridge and the tv, etc. There it sits
waiting for the next hurricane. A 250W system that would keep this rig
'exercised' while I'm at work would pay for itself in a couple of
years. I've been ruminating on how to make one... I think driving the
12v secondary of a 250 watt transformer with a varaiable ampl and freq
pwmmed sine wave might work. Cant quite dial in on how to stay in sync
though... ideas?
Mauried
wrote:
You cant make a grid Tie Inverter, at least not one that any electric
supply utility will approve, and without approval, you cant connect it
to the mains.
A lot of the costs in grid Tie Inverters is the accreditation and
safety checks needed before power utilites will allow their use.
A Grid Tie Inverter wont help at all during power blackouts.
Maury Markowitz
> What do you want to test? That panels make electricity? They do. That
> an inverter will turn ELV into HV? They do.
No. I'm a physicist and I want to test off-axis power generation using
aSi vs. conventional polySi.
> Get real.
Pfft. Thanks for the great advice, it's really useful. Not.
*PLONK*
Maury
Maury Markowitz
wrote:
> Because they are no practical use to man nor beast.
That doesn't seem to be the case. In fact, after broadening my search
I was able to find a wide variety of such systems, unfortunately they
are all european 240/50Hz. They are also designed to plug directly
into a mains socket, so installing the panels consists of nothing more
than plugging the panels into the inverter, the inverter into any
nearby socket, done.
If only that was true here...
Maury
BobG
> You cant make a grid Tie Inverter, at least not one that any electric
> supply utility will approve, and without approval, you cant connect it
> to the mains.
> A lot of the costs in grid Tie Inverters is the accreditation and
> safety checks needed before power utilites will allow their use.
> A Grid Tie Inverter wont help at all during power blackouts.
Oh Poo. Its 250 watts fer gods sake. Its just a little trickle. No one
will know its there. No need to ask for approval. Its easy to tell
when the rest of the world turns off... the output current limits on
the next cycle. Its the 'normal' case thats sort of hard to
understand.
Eeyore
Maury Markowitz wrote:
> Eeyore wrote:
>
> > Because they are no practical use to man nor beast.
>
> That doesn't seem to be the case. In fact, after broadening my search
> I was able to find a wide variety of such systems, unfortunately they
> are all european 240/50Hz. They are also designed to plug directly
> into a mains socket, so installing the panels consists of nothing more
> than plugging the panels into the inverter, the inverter into any
> nearby socket, done.
But low-power ? That's what I meant about 'no practical use'. Larger ones,
say 500W and up I can see the point
Graham
Eeyore
Maury Markowitz wrote:
> They are also designed to plug directly
> into a mains socket, so installing the panels consists of nothing more
> than plugging the panels into the inverter, the inverter into any
> nearby socket, done.
Right, in which case they auto 'drop-out' in case of grid failure. It's
simple and effective but gives you no back up.
Graham
z
news:c1514436-2230-4fcc...@t54g2000hsg.googlegroups.com:
> On Jun 20, 8:36 am, maur...@tpg.com.au (Mauried) wrote:
>> You cant make a grid Tie Inverter, at least not one that any electric
>> supply utility will approve, and without approval, you cant connect
>> it to the mains.
>> A lot of the costs in grid Tie Inverters is the accreditation and
>> safety checks needed before power utilites will allow their use.
>> A Grid Tie Inverter wont help at all during power blackouts.
> ===========================================Oh Poo. Its 250 watts fer
> gods sake. Its just a little trickle. No one will know its there. No
> need to ask for approval. Its easy to tell when the rest of the world
> turns off... the output current limits on the next cycle. Its the
> 'normal' case thats sort of hard to understand.
>
Yeah no one will know its there until the utility company needs to do work
on a line and shuts it off -- and your 250 watts is still flowing making
the line hot when they work on it.
Then you've got some pissed off utility guys.
BobG
> Yeah no one will know its there until the utility company needs to do work
> on a line and shuts it off -- and your 250 watts is still flowing making
> the line hot when they work on it.
>
> Then you've got some pissed off utility guys.
Wait a minute... line shuts off, that condition is abundantly obvious
1/60th of a second after it occurs.... open circuit... no current
flowing. The other condition, trying to run the whole neighborhood is
also easy to detect... not enough juice for the next cycle. So I see
no problem with these two situations. Wouldnt want to PO any power
company employees. How bout some brainstorming on synch and connect
algos instead of 'naaaah... you cant do that... even if you're smart
enough, theres someone up the chain that will say no if you ask...'?
That's the Intellectual Property that the inverter mfgrs seem to be
keeping close to their vests.
Eeyore
z wrote:>
> Yeah no one will know its there until the utility company needs to do work
> on a line and shuts it off -- and your 250 watts is still flowing making
> the line hot when they work on it.
>
> Then you've got some pissed off utility guys.
That would be a a non-compliant grid-tie inverter.
Gragam
We Can Do It
"Eeyore" <rabbitsfriend...@hotmail.com> wrote in
message news:485C0359...@hotmail.com...
And at least in GA USA you are required to register any NUG
( non utility generators) with the power company or you are
breaking the law. You want to do this here since the power
company will change out your metering and make it bi
directional ( at your expense ) and provide and register a
disconnect they can controll ( at your expense) and have you
sign liability waivers. The up side is that in the event you
actually put power back on the grid they pay your about double
what they charge you to take it off the grid.
peace
dawg
>
>
BobG
> And at least in GA USA you are required to register any NUG
> ( non utility generators) with the power company or you are
> breaking the law. You want to do this here since the power
> company will change out your metering and make it bi
> directional ( at your expense ) and provide and register a
> disconnect they can controll ( at your expense) and have you
> sign liability waivers. The up side is that in the event you
> actually put power back on the grid they pay your about double
> what they charge you to take it off the grid.
I use 30kwhr a day. If I pump 2kwhr back in while the sun is shining,
how's the power company going to know?
Eeyore
We Can Do It wrote:
> The up side is that in the event you
> actually put power back on the grid they pay your about double
> what they charge you to take it off the grid.
Yeah.
Phoney economics. It'll never last when the numbers get big unless you
want to pay 30c / kWh.
Graham
Martin Riddle
"BobG" <bobga...@aol.com> wrote in message news:148433da-623c-47a1...@s50g2000hsb.googlegroups.com...
Syncing easy, PLL.
For line dropouts, you can warble the frequency, as the phase of the two systems change you'll see the power increase.
If its an island effect, you will not see the power increase(since the other inverter is syncing to yours) and you shutdown.
Cheers
Richard P.
http://www.buyerisland.net/greenpower.htm
"Maury Markowitz" wrote in message
Anthony Matonak
...
> I use 30kwhr a day. If I pump 2kwhr back in while the sun is shining,
> how's the power company going to know?
They don't have to know for certain. If they suspect, they can
switch out your old style meter that spins both ways with something
else. They have versions that don't spin backwards or electronic
versions that bill you for the amount of power flowing through them,
regardless of which direction it's flowing.
Anthony
BobG
<anthony...@nothing.like.socal.rr.com> wrote:
> They don't have to know for certain. If they suspect, they can
> switch out your old style meter that spins both ways with something
> else. They have versions that don't spin backwards or electronic
> versions that bill you for the amount of power flowing through them,
> regardless of which direction it's flowing.
Progress Energy in Florida has some sort of wireless electronic meter
that can be read from out in the truck on the street. Guess they
couldn't find enough meter readers that could jump fences, wrassle
with pit bulls and read dial meters where every other dial turned a
different direction.
Roderick
I agree that the device you list is illegal practically anywhere in
the US. But then again, so is the DIY way that some people wire an
extra circuit into their garage or attic. I'm not condoning this sort
of thing, but it would probably work.
Will it turn the meter backwards? Assuming the device actually does
work, it should. Most meters are bidirectional, whether designed that
way or not. The old clock-type meters generally don't have a one-way
ratchet on them because the issue of someone driving power back into
the lines was nonexistent until recently. The only time a one-way
meter would be installed was if they caught someone driving power in,
or a homeowner asked about it. In states that net-meter, the digital
meter goes both ways, of course. I suspect you'll be disappointed by
the amount of power the device puts out. To actually see the meter
turn backwards, you may need to get rid of all the phantom loads in
your house by flipping off the circuit breakers for everything except
your device. The various clocks and power bricks around the house can
add up to hundreds of watts - more than your inverter can put out.
Every once in a while, the idea of micro-inverters seems to surface
again, in the form of a tiny inverter embedded in each panel, or for
every few panels. The idea is that if one or more panels is shaded,
the only power lost is for that panel, and not the whole string. It
sounds like a great idea, but I have to ask, why would someone install
panels where they knew there would be shade at some time during the
day?
Vaughn Simon
"Richard P." <n...@home.eh> wrote in message
news:r__6k.15614$kx.12206@pd7urf3no...
> Maury, there is this item that may answer your question:
> http://www.buyerisland.net/greenpower.htm
Bingo! Give that man the prize.
Vaughn
Neon John
>Oh Poo. Its 250 watts fer
>> gods sake. Its just a little trickle. No one will know its there. No
>> need to ask for approval. Its easy to tell when the rest of the world
>> turns off... the output current limits on the next cycle. Its the
>> 'normal' case thats sort of hard to understand.
>>
>
>Yeah no one will know its there until the utility company needs to do work
>on a line and shuts it off -- and your 250 watts is still flowing making
>the line hot when they work on it.
>
>Then you've got some pissed off utility guys.
You're kidding, right? 250 watts wouldn't even supply the magnetizing power
for the first pole pig, much less charge a few hundred feet of primary's
capacitance. It probably wouldn't even supply the phantom loads in the house
itself.
BobG, I'd go looking at semiconductor application notes and then maybe try to
scrounge up a grid-tie inverter schematic.
It actually shouldn't be difficult - just phase-lock the local 60 hz
oscillator to the grid frequency and then make sure you turn on the right
polarity :-) Let the inverter voltage rise above the line until the inverter
is fully loaded.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
I'm so cool, I'm afraid to catch cold.
Neon John
Come on, guys, THINK. Just a little bit. OK?
If he's using 20kWh a day and his itty bitty solar inverter is making 2kWh a
day, that means that his meter registers 18 kWh a day instead of 20. It
doesn't turn backwards. It simply turns forward a bit slower. Duh!!!
The only time it could possibly turn backwards is if the total draw of his
entire house is <= 250 watts. Chance of a fart in a whirlwind if he's using
20 kWh a day!
BobG, you know, the easiest thing to do with those 250 watts might be to power
an extra heating element in your water heater. It MIGHT make up for standby
losses.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
It isn't Global Warming.... It's Jerry Falwell arriving in hell.
Neon John
>Progress Energy in Florida has some sort of wireless electronic meter
>that can be read from out in the truck on the street. Guess they
>couldn't find enough meter readers that could jump fences, wrassle
>with pit bulls and read dial meters where every other dial turned a
>different direction.
Gee, y'all are behind the times! Our little hillbilly rural co-op has
installed electronic modules that read the wheel rotation of good old reliable
electromechanical meters and phones home about twice a day over the power
line. Google for the "turtle system".
The only minor deficiency is that backward wheel movement counts as forward
power since the photo eye isn't direction-sensitive. Not really a problem
here cuz I doubt that anyone is co-genning. If someone ever does, they simply
install a separate meter that will ONLY turn backwards and subtract the two
readings.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Beware the lollipop of mediocrity. Lick once and you suck forever.
Bruce Harvey
that you don't black out your whole area. You seem to forget that your end
might only be 250W but at the other end of that line is a base load
generator or 2 (Or a lot more) putting out Gigawatts of power. Those
generators are all synchronized together for a reason. your 250 watts is
probably gust enough to bring down the whole grid. Wake up to yourself and
learn a bit more about electricity. I don't know much but I know that you
are only going to cause trouble if you put unsynchronized power into the
grid. Anyway if you do try you might find yourself eligible for a Darwin
award at least.
spaco
Anyone who puts in panels without tracking across the sky has this
problem to some extent.
Right now the sun is shining brightly in western Wisconsin and I am
generating only 5% of what will be coming in at noon. I estimate that
I loose about 37% of the sun in a day due to excessive angles that, I
suppose, could be eliminated with panels at various angles, if they
weren't so expensive. And that's in March. I must be loosing even more
now in June.
Pete Stanaitis
---------------------
Maury Markowitz
> Will it turn the meter backwards?
Not an issue.
There are two separate goals here. One is to directly compare two very
different technologies in order to see if the claims of the aSi crowd
are what they say. The second is to _begin_ the process of starting a
grid-tie system, as Ontario now offer an extremely lucrative .42/kWh
price for PV fed into the grid. I'm not sure how long this offer will
last, so I want to get started as soon as possible. Once I've
convinced myself of the statistics, one way or the other, I'll finish
the buildout by covering my garage roof. Using either technology I
should end up with about 2 to 3 kWh peak.
As it seems there are no appropriate solutions in this space, I'm
currently thinking of just attaching the panels to a string of 100 w
incandescent light bulbs with a Kill-o-watt meter. I am a little upset
that the energy created in this process will go entirely to waste,
especially because it's during the "light soak" time when they're
producing more than average energy.
Maury
Maury Markowitz
> BobG, you know, the easiest thing to do with those 250 watts might be to power
> an extra heating element in your water heater. It MIGHT make up for standby
> losses.
Ahhhh, now there's an idea. Of course it still requires an inverter of
some sort... but I think I have just the thing to be honest, a 12 vDC
box intended to allow running of power tools off of car batteries.
Yes, I think I have a plan here...
Maury
Uncle Ben
> I'm in the process of starting my first PV install, and to start with
> I want to start with a simple two-panel install to test them head-to-
> head. Since there are only two panels, even the series voltage will be
> quite low. All of the inverters I've seen want high input voltages
> (and it appears higher voltages are more efficient?).
>
> So can anyone recommend an inverter useful for a single 18 VDC panel?
> Is there such a thing?
>
> Maury
Maury, you surely are aware of the small inverters available widely in
computer stores that produce 120 VAC from 12 VDC. They are used for
charging your laptop battery and other things from you car. The price
is proportional to the power-handling ability down to as low as $50.
Maybe one would be useful to you for testing purposes.
Ben
daestrom
I can't tell if you're being sarcastic or not (no smiley??)
Hooking a 250 watt inverter to *the grid* in phase, out-of-phase or any
which phase will do nothing to the grid. Most it would do is trip the
circuit breaker in the basement.
daestrom
BobG
> "BobG" <bobgard...@aol.com> wrote in message
>
> news:c1514436-2230-4fcc...@t54g2000hsg.googlegroups.com...
> On Jun 20, 8:36 am, maur...@tpg.com.au (Mauried) wrote:> You cant make a grid Tie Inverter, at least not one that any electric
> > supply utility will approve, and without approval, you cant connect it
> > to the mains.
> > A lot of the costs in grid Tie Inverters is the accreditation and
> > safety checks needed before power utilites will allow their use.
> > A Grid Tie Inverter wont help at all during power blackouts.
>
> ============================================
> Oh Poo. Its 250 watts fer gods sake. Its just a little trickle. No one
> will know its there. No need to ask for approval. Its easy to tell
> when the rest of the world turns off... the output current limits on
> the next cycle. Its the 'normal' case thats sort of hard to
> understand.
written by Bob G
========================================
written by BH
> That's why they have laws to stop people like you connecting to the grid so
> that you don't black out your whole area. You seem to forget that your end
> might only be 250W but at the other end of that line is a base load
> generator or 2 (Or a lot more) putting out Gigawatts of power. Those
> generators are all synchronized together for a reason. your 250 watts is
> probably gust enough to bring down the whole grid. Wake up to yourself and
> learn a bit more about electricity. I don't know much but I know that you
> are only going to cause trouble if you put unsynchronized power into the
> grid. Anyway if you do try you might find yourself eligible for a Darwin
> award at least.
===================================================
I see you using the word 'unsynchronized' in your reply to my message.
I have taken the liberty of separating my words from yours. God forbid
someone would think I issued those comments. Of course, none of my
messages contain that word, so I think you are confused.
Bruce Harvey
Possibly my bad. I maybe misunderstood. I was under the impression from what
I was reading here that the inverter would be connected to a GPO (regular
power outlet) without synchronizing it with the grid. If this is not the
case then I apologize. As mentioned in other posts in this thread the use of
a grid tied inverter is regulated by the law and the utility companies. The
reasons for this are many but mainly for the safety of utility workers and
for the reliability and quality of the grid output. Connecting anything to
the grid here in Australia is regulated by law and all equipment must be
approved for safety reasons. I gather it is a similar setup in the US and
most other countries as well.
The Darwin Award comment was meant to reinforce the danger of doing such a
thing as connecting unsynchronized power to the grid.
Duane C. Johnson
The basic methodology is not to hard to do.
There are several strategies that may be used but I
think one of the best is like this.
1. Use a PLL oscillator with the frequency set to
60.5 to 61 Hz.
2. Have the oscillator reset back to synchronization
each time the line voltage passes through zero
120 times per second.
3. When the "island" is disconnected from the grid
the inverter will immediately try to go to a
frequency higher than 60Hz.
4. A. Trip the breakers when the measured frequency
is out of specification.
B. Trip the breakers when the measured voltage
is out of specification, either high or low.
C. Trip the breakers when the measured current
is out of specification.
I don't remember the timing specifications of
UL 1741, and others, but I recall that it must trip
after about 2 seconds when the inverter is out of
tolerance.
OK, now the cool totally improper method.
Kids don't do this without adult supervision.
You don't need to be synchronous with the grid in
any way to send power back to the grid.
I did some experiments to learn about grid tie
techniques. I used a high end Yokogawa AC power
meter and a high power current source. I also
had a conventional mechanical KWHr meter. ( disk
type.)
This was connected to the grid and supplied with
an AC power source. The source was a 100kW
Pacific Power electronic amplifier designed to
power our computer for compliance tests.
This amplifier is essentially a huge power
amplifier capable of out AC, DC, and any other
wave shape including square waves at up to about
280 volts.
I injected current into the grid through the
power meter. I could vary the frequency and
wave shape up to about 800Hz and directed the
power meter and KWHr to measure the power and
direction of flow.
I injected the current and showed that power
always flowed to the grid. No mater what the
phase, frequency, voltage or wave shape was.
Further, the mechanical power meter performed
correctly and successfully measured the power and
directly. At least up until higher frequencies
above 500Hz
Duane
--
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Don Kelly
"Bruce Harvey" <bl.h...@bigpond.com> wrote in message
news:KhW7k.13989$IK1....@news-server.bigpond.net.au...
>
> "BobG" <bobga...@aol.com> wrote in message
> news:a5d9f7c4-1173-4181...@f63g2000hsf.googlegroups.com...
Daestrom is correct- a 250W inverter will do nothing to the grid- it won't
even notice it. However the inverter will notice it- and there is definite
chance of letting the magic smoke out of the inverter (or, preferrably,
tripping the breaker). Bob G might find that turning a "stand alone"
inverter into garbage is expensive although the utility won't notice such a
small unit.
If a GW system is so close to the stability point that a 250W inverter
out of phase can bring it down, then don't switch on (or off) the tea kettle
until you have your candles on hand. (typically the system is not operated
anywhere near either the steady state or the transient stability limit by at
least a factor of 2 ).
Proper "grid tie" inverters are automatically synchronized to the grid
(protecting the inverter -not the grid). In some the local oscillator is
the grid and in others, the grid voltage is sensed and the phase of the
local oscillator adjusted automatically to match.
Safety concerns are there but they are not related to
synchronization/blackouts. Most are related to energization of lines that
are expected to be "dead" and proper practice is to ground these lines (on
both sides of the work area) before working on them- not just assuming that
there is no back feed. That might just take care of (overload) an illicit
small converter.
While I suspect that a 250W inverter plugged into an outlet will not be
able to handle the magnetizing current of the local utility transformer, the
regulations in Canada and the US, as in OZ err on the safe side as they
should. This means that there should be no connection to the grid that is
not approved- at any level- which is what you have said.
--
Don Kelly dh...@shawcross.ca
remove the X to answer
>
Neon John
You can get low voltage heating elements for water heaters. They're commonly
used as energy dump loads for micro-hydro plants. No idea of the cost.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Some people are like a Slinky .. not really good for anything
but you still smile
when you shove them down the stairs.
We Can Do It
On Jun 20, 4:02 pm, "We Can Do It" <Ca...@motivation.com>
wrote:
> And at least in GA USA you are required to register any NUG
> ( non utility generators) with the power company or you are
> breaking the law. You want to do this here since the power
> company will change out your metering and make it bi
> directional ( at your expense ) and provide and register a
> disconnect they can controll ( at your expense) and have you
> sign liability waivers. The up side is that in the event you
> actually put power back on the grid they pay your about
> double
> what they charge you to take it off the grid.
================================
how's the power company going to know?
A) If you engineer and build your small grid tie system and
initiate the final connection by GA code, then in accordance
with GA law the power company puts a meter on your house that
tells them how many KWH you provided to the grid. GA power
then charges you to read that meter and by law GA Power pays
you 17.4 cents/KWH for the power you put back into the grid. I
am not saying you will get your investment back, just that it
works this way if you follow the letter of the law and GA
Power pays more for the "green energy" than they charge you
for standard grid energy.
peace
dawg
BobG
> the power company puts a meter on your house that
> tells them how many KWH you provided to the grid.
So if my usage per day goes from 30 to 28kwhrs, I'm not providing any
power to the grid, therefore they dont know nuthin.
Daniel Who Wants to Know
"Don Kelly" <dh...@shaw.ca> wrote in message
news:wJZ7k.23263$kx.13092@pd7urf3no...
> ----------------------------
The simple non electronic (albeit less efficient) way to feed power back
would be to have a good DC motor coupled to a standard induction motor.
Most people don't realize that induction motors instantly turn into
generators if you use an external source to attempt to turn the shaft faster
than the synchronous speed and assuming you don't have any capacitors
connected in parallel will simply stop generating and allow the shaft to
spin free when the grid power goes down.
Vaughn Simon
"Daniel Who Wants to Know" <danielt...@merrychristmasi.com> wrote in
message news:u9j8k.170469$TT4.88773@attbi_s22...
>
> The simple non electronic (albeit less efficient) way to feed power back would
> be to have a good DC motor coupled to a standard induction motor. Most people
That is exactly how it was done on nuclear submarines back in my Navy days.
But that is old technology and we have better ways of doing it now.
Vaughn
Solar Flare
"Vaughn Simon" <vaughnsimo...@att.FAKE.net> wrote in message
news:mLo8k.140730$SV4....@bgtnsc04-news.ops.worldnet.att.net...
daestrom
Ugh... no it wasn't. The MG sets on nuc submarines were *synchronous*
motors on the AC side, not *induction* motors. These could reverse power
flow just as easily but provided much better voltage and frequency
regulation when running isolated from the turbine-generator to power the
vital busses.
daestrom
Vaughn Simon
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:g3ua7...@news3.newsguy.com...
>
> Ugh... no it wasn't. The MG sets on nuc submarines were *synchronous* motors
> on the AC side, not *induction* motors. These could reverse power flow just
> as easily but provided much better voltage and frequency regulation when
> running isolated from the turbine-generator to power the vital busses.
I was talking more about the general principle, but you are more precisely
correct, the AC side was a synchronous motor. In fact, back then I had no idea
that an induction motor could serve as an AC generator.
Most folks automatically figure that the motor would have to reverse
direction to switch the direction of power flow, but that is not the case. In
fact, they would happily go instantaneously from float to supplying full power
to the power buss with barely a grunt. They were the perfect UPS (for the
technology of the times).
We also used another bit of old technology that you can still find in UPSs,
the resonant (Sola) transformer. We used a SOLA transformer (with it associated
capacitor) to store just enough energy to carry us for a Hz or two while a
mechanical relay switched power busses.
Vaughn
daestrom
Yep. Also regulated the output to NI's and PPI's despite voltage dips on
the vital bus. Mag-amps hated voltage variations.
daestrom
(remember, "When taking reactor protection from 'coincident' to 'single'
protection, *always* go through 'starboard test', *never* through 'port
test'." If you know what that means, you *are* an old salty dog submariner
:-)
daestrom
Or was it always go through 'port test'?? Now I can't remember.
Don Kelly
"Daniel Who Wants to Know" <danielt...@merrychristmasi.com> wrote in
message news:u9j8k.170469$TT4.88773@attbi_s22...
>
Sure, that is an old technology. It works quite elegantly and simply but at
low levels it is large, clumsy and inefficient compared to a properly
designed (and connected) grid tie inverter.
Induction generators were (and may still be ) used in Scotland on small
hydro projects.Start the motor (remotely)at no load, open the gates and as
the water takes the speed over synchronous -you have power. I know of one
place where induction motors are used to pump from a reservoir into a canal
feeding a hydro plant (better efficiency of the plant at a constant head)
and when the reservoir was high, running the motors as generators rather
than just spilling into the canal. Note that this utility also used
compressed air to dewater a turbine when the unit was running as a
synchronous capacitor -saving some energy. It was cost effective in both
cases.
Note that the machine needs sufficient reactive support from the system to
provide its excitation.
Cydrome Leader
> On Fri, 20 Jun 2008 11:17:43 -0500, z <z...@yada.yada.com> wrote:
>
>>Oh Poo. Its 250 watts fer
>>> gods sake. Its just a little trickle. No one will know its there. No
>>> need to ask for approval. Its easy to tell when the rest of the world
>>> turns off... the output current limits on the next cycle. Its the
>>> 'normal' case thats sort of hard to understand.
>>>
>>
>>Yeah no one will know its there until the utility company needs to do work
>>on a line and shuts it off -- and your 250 watts is still flowing making
>>the line hot when they work on it.
>>
>>Then you've got some pissed off utility guys.
>
> You're kidding, right? 250 watts wouldn't even supply the magnetizing power
> for the first pole pig, much less charge a few hundred feet of primary's
> capacitance. It probably wouldn't even supply the phantom loads in the house
> itself.
this sounds pretty accurate. The inrush current to even power on a small
distribution transformer is extremely high and would make any small
inverter just shut down thinking it was shorted out.
z
news:g43db0$mkm$1...@reader2.panix.com:
you guys are probably right.
I just remember several times during my wildland firefighting days seeing
down lines and hearing over the radio 'yeah they're not hot' and hoping
some asshole hadn't plugged in a generator somewhere down the line as we
began hitting the area with water.
Neon John
>>> You're kidding, right? 250 watts wouldn't even supply the
>>> magnetizing power for the first pole pig, much less charge a few
>>> hundred feet of primary's capacitance. It probably wouldn't even
>>> supply the phantom loads in the house itself.
>>
>> this sounds pretty accurate. The inrush current to even power on a
>> small distribution transformer is extremely high and would make any
>> small inverter just shut down thinking it was shorted out.
>>
>
>you guys are probably right.
>
>I just remember several times during my wildland firefighting days seeing
>down lines and hearing over the radio 'yeah they're not hot' and hoping
>some asshole hadn't plugged in a generator somewhere down the line as we
>began hitting the area with water.
I'm a retired utility engineer and before that a lineman. IOW, a little
experience in this area.
A couple of comments.
ANY wire that you can't clearly see both ends of is considered hot until
rendered safe with grounds. As a lineman, I'd never touch even a downed guy
wire without my hot gloves on. If someone was telling you that a line was OK
because it wasn't hot, that person had a death wish for you. Even if the line
were dead at the moment, it could go hot at any second, either automatically
or because someone made a switching mistake.
Other comment: Water isn't conductive enough to present a shock hazard from a
fire hose or something similar even if the line is hot. It was a routine
practice to use fire hoses down live 500kV insulators at the power house
switch yard to remove crud buildup. I couldn't believe it the first time I
saw it but I learned that it is a routine procedure.
Now if you were using one of those back pack water bladders that the hotshots
use, different story. You don't want to "pee" on the power line!
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
No one can be right all of the time but I'm getting close.
Bruce in alaska
Cydrome Leader <pres...@MUNGEpanix.com> wrote:
> this sounds pretty accurate. The inrush current to even power on a small
> distribution transformer is extremely high and would make any small
> inverter just shut down thinking it was shorted out.
Just a Note here, When we are considering Islanding and Backfeeding,
one thing to consider IS, that if some Yahoo does "accidently" Plug
his 2Kw Genset into a house with the Main Breaker Still on during
an outage, it isn't the 2Kw of power that is going to travel back up
the Distribution System, but the Voltage Spike that that 2k Genset
is going to cause, untill either it's internal Breaker Trips, or the
Magic Smoke pours out of the Genend. It will be the spike that
zaps the folks up the line. Yes, ALL Linemen, know what Grounding Staps
are for, and use them, as well as Hot Sticks, Hv Gloves, and all the
other protective gear associated with Power Transmission Systems,
BUT, the NEC REQUIRES Transfer Switches and Anti-Islanding Devices
for a reason, and it IS really, Safety Related.
--
Bruce in alaska
add <path> after <fast> to reply
Neon John
Well, there's safety and there is blind dumbshit idiocy that ignores common
sense masquerading as safety. Much of the NEC is in that category.
Before a 2kW generator can do anything to that lineman down the road who is
careless enough to be handling a conductor without his gloves and without
grounds, it first has to power up the house, any other houses connected to the
pig, the magnetizing current of the pig, the capacitance loading of the
primary, the magnetizing current of any other pig on the "island, any other
houses on any other pig, etc, excess...
Ain't gonna happen. What the generator sees is essentially a dead short. With
most small generator designs, the field de-excites and the generator does
nothing. The only time that islanding is even a remotely credible hazard is
if someone is at the end of a long primary line in a rural setting and the
primary line is downed near the pig feeding the facility. A large farm might
fit that description. A large farm is likely to also have a PTO-driven or
stationary 20kW or larger generator. Even if he did manage to backfeed and
energize the primary, when the first lineman on the scene does what every
lineman is trained to do automatically, secure grounds, the generator is
dead-shorted.
That's really not what this thread is about since we were discussing a 250
WATT inverter and not a 2kW one. There has been so much yammering that I
decided to do an experiment. I went down to my shop and rolled out a 20kVA,
14.4kV pole pig (doesn't every shop have one or two?) I don't have a 250 watt
inverter but I do have several 350 watt ones.
The experiment consists of hooking the inverter to a pair of 100 amp-hour 12
volt deep cycle batteries in parallel to make sure there is enough inrush
available on the 12 volt side. A 120 volt Jesus cord runs directly from the
inverter to the neutral and one hot leg of the pig's secondary. The primary
is unconnected except for a short jumper leading over to an electrostatic
kilovoltmeter. An electrostatic meter has infinite impedance and presents no
load.
I did 10 shots. That is, with everything wired up, I flipped the inverter
switch to "on". Ten out of ten times the inverter tripped instantly. The
voltmeter didn't move a bit. I guess that I could have hooked a scope and HV
probe to the primary but it wouldn't have told me much more. Obviously the
inverter's protective circuitry trips it off long before it can complete even
a single cycle.
I tried the same experiment with a 1.5kW inverter that I had handy. Same
result except that I could see just a blip on the electrostatic voltmeter.
Maybe a half-cycle of output completed before this inverter shut down.
This pole pig is extremely efficient. I once measured the standby losses. I
don't recall the exact number but it was something tiny, on the order of 10
watts or so. HOWEVER! It needs several kVA of magnetizing "wattless" power.
That's the demand the inverter sees and can't supply.
This experiment on a pole pig with NOTHING attached to it shows just how silly
it is to be discussing back-feeding from a 250 watt inverter.
I know from other experience that it is very difficult, almost impossible, to
energize this pig even from a 7kVA generator by closing the breaker once the
generator is up to speed. That makes it kinda difficult to feed a large
Jacob's ladder from the generator. The only way that I can make it work is to
close the breaker before starting the generator. Then, most of the time, they
come up together.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
I like you ... you remind me of me when I was young and stupid.
Duane C. Johnson
> On Sat, 28 Jun 2008 20:12:42 GMT, Bruce in Alaska <fa...@btpost.net> wrote:
>
>
>>In article <g43db0$mkm$1...@reader2.panix.com>,
>>Cydrome Leader <pres...@MUNGEpanix.com> wrote:
>>
>>
>>>this sounds pretty accurate. The inrush current to even power on a small
>>>distribution transformer is extremely high and would make any small
>>>inverter just shut down thinking it was shorted out.
>>
>>Just a Note here, When we are considering Islanding and Backfeeding,
>>one thing to consider IS, that if some Yahoo does "accidentally" Plug
>>his 2Kw Genset into a house with the Main Breaker Still on during
>>an outage, it isn't the 2Kw of power that is going to travel back up
>>the Distribution System, but the Voltage Spike that that 2k Genset
>>is going to cause, until either it's internal Breaker Trips, or the
>>Magic Smoke pours out of the Genend. It will be the spike that
>>zaps the folks up the line. Yes, ALL Linemen, know what Grounding Straps
Hi John;
I like your ingenuity in performing this experiment.
Thanks!
But, (there is always but).
I was thinking that your test into what amounts to be
a dead short might not be the case that UL-1741 is
testing for.
The grid tie inverter should be assumed to be driving
the pig in an already energized condition. I would
guess that the inverter could keep up with the small
losses once running.
Is there a way you could try to do your energizing test
again. Except this time try to get the transformer
humming before you directly connect the inverter.
You might do this by initially placing a resister in
series to get it going. To do the test with your
350W inverter I would try a 100W incandescent lamp
for the resister.
It would be nice to see if the transformer currents
could be maintained after energization.
Thanks!
Vaughn Simon
"Duane C. Johnson" <red...@redrok.com> wrote in message
news:4866c64e$0$18422$39ce...@news.twtelecom.net...
>I would try a 100W incandescent lamp
> for the resister.
3-100W lamps would be better, but I wonder how valid the test would be unless
you are using a sine wave inverter.
This is turning into an interesting thread! I also thank John for performing
the experiment.
Vaughn
Don Young
expert opinion, backfeeding the power lines is impossible with a small
inverter or generator and even if it were it poses no hazard to anyone
important. Anyone who has been electrocuted by this was so dumb that he
deserved what happened and it was not the fault of anyone else. If your
power is off because your service drop is lying on the ground in a storm,
everyone knows not to touch it. The NEC requirements are nonsense and should
be totally disregarded in this case."?
There has been a lot of discussion and rationalization on this subject over
many years but I still haven't heard why anyone should (as opposed to could)
energize their home electrical system without a functional transfer system.
Don Young
stu
"Don Young" <no...@nonesuch.com> wrote in message
news:EJqdnYHR6utBcPvV...@posted.worldwebinternetservicesprovideinc...
In this case the subject line says it all "Small grid-tie inverters". A
"functional transfer system" would make it "Small non-grid-tie inverters"
Nice test NJ, I want a shed like yours.
z
news:486701b6$0$30466$afc3...@news.optusnet.com.au:
Yeah its amazing how much I learn from these newsgroups from time to
time.
cheers
Neon John
<oral diarrhea snipped>
>There has been a lot of discussion and rationalization on this subject over
>many years but I still haven't heard why anyone should (as opposed to could)
>energize their home electrical system without a functional transfer system.
Even this sentence makes no sense or maybe you're functionally illiterate.
No one neither could nor should try to power up his house without a transfer
switch for all the reasons discussed in this thread. Top of the list of
reasons is, he can't.
If what you're trying to say is that you haven't heard why someone should use
his generator without buying a fancy transfer switch with all the stamps and
approvals and even the blessings from the right hand of God, well, here's a
reason.
Two, actually. I don't need one and I don't want one. I was born with enough
good old fashioned common sense to be able to flip off one breaker labeled
"main" and flip on another breaker labeled "generator". So far I've done that
tens, maybe hundreds if times without getting it wrong. Not even once,
amazing as it may seem of a task about as complicated as sticking the right
leg in the right hole in your pants in the morning.
At least with me doing the switching, I know that it's done right. Not
necessarily so if I rely on that fancy enclosed transfer switch. On more than
once occasion I've seen an enclosed disconnect switch fail. The little fiber
finger that operates the blade on the knife switch breaks and that switch
stays engaged. The handle says "OFF" but the electrons say "ON"!
On one occasion that left one phase of a 480 volt, 3 phase feed to a control
panel energized. Had I not been the highly trained and careful individual
that I am, I might have been killed. Just like a careless lineman.
True, the odds of that kind of failure happening are rare but then again, the
odds of me screwing up my two-motion manual generator transfer operation are
even rarer.
You seem to be a fellow who need a lot of authority in his life. I
understand. Managing one's affairs is something that few people do well. For
you, they have those fine and expensive transfer switches. For the rest of
us, we'll get along fine without 'em.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
If stupidity hurt then they'd be putting morphine in the water supply.
Cydrome Leader
I've noticed that generator and datecenter UPS transfer switches seem far
more complicated than they should be. It gets even more fun when you have
both of those and internal or soft bypass switches inside the UPS itself.
Vaughn Simon
"Cydrome Leader" <pres...@MUNGEpanix.com> wrote in message
news:g49pt6$q$1...@reader2.panix.com...
> I've noticed that generator and datecenter UPS transfer switches seem far
> more complicated than they should be. It gets even more fun when you have
> both of those and internal or soft bypass switches inside the UPS itself.
UPS is an overused technology. Millions of $ are wasted buying them, and
megawatt-hours of power is wasted on the power losses of unnecessary UPS
installations. Any UPS system represents a potential point of failure. I have
seen more data closets fail because of UPS failure than any other single item.
And yes, I have seen transfer switches fail too... One notable example was in
the middle of a hurricane. In that particular incident, we would have been far
better off without it, since it left a public safety radio system for a medium
size city dead until a suitably qualified human could brave the storm and
manually unjam the switch.
It is simple math. The more equipment you have, the more equipment failures you
can expect (MTBF).
Vaughn
Cydrome Leader
>
> "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
> news:g3ua7...@news3.newsguy.com...
>>
>> Ugh... no it wasn't. The MG sets on nuc submarines were *synchronous* motors
>> on the AC side, not *induction* motors. These could reverse power flow just
>> as easily but provided much better voltage and frequency regulation when
>> running isolated from the turbine-generator to power the vital busses.
>
> I was talking more about the general principle, but you are more precisely
> correct, the AC side was a synchronous motor. In fact, back then I had no idea
> that an induction motor could serve as an AC generator.
>
> Most folks automatically figure that the motor would have to reverse
> direction to switch the direction of power flow, but that is not the case. In
> fact, they would happily go instantaneously from float to supplying full power
> to the power buss with barely a grunt. They were the perfect UPS (for the
> technology of the times).
They still make flywheel UPSes. The market for these seems to be factories
or places with lighting that cannot restart instantly after power loss.
The flywheel spins for X seconds or whatever it takes to switch to your
generator. High speed transfer switches for switching between different
utility feeds seems to be a big deal for the same reason.
> We also used another bit of old technology that you can still find in UPSs,
> the resonant (Sola) transformer. We used a SOLA transformer (with it associated
> capacitor) to store just enough energy to carry us for a Hz or two while a
> mechanical relay switched power busses.
I've not seen any modern ferroresonant UPSes, probably because of their
efficiency, but for plain and good quality power conditioning,
ferroresonant transformers cannot be beat. No solid state power converter
comes with 20 or 25 year warranties.
Vaughn Simon
"Cydrome Leader" <pres...@MUNGEpanix.com> wrote in message
> I've not seen any modern ferroresonant UPSes, probably because of their
> efficiency, but for plain and good quality power conditioning,
> ferroresonant transformers cannot be beat. No solid state power converter
> comes with 20 or 25 year warranties.
They still make them, but you are buying ancient technology. Against my
better judgment, I replaced one with a brand new unit just last week. Best
Power is now Powerware. Ferroresonant transformers seem to have very high core
losses. I have a Sola regulator here in my study that would make a good foot
warmer. Judging from the temperature rise, it must vampire 20 or 30 watts 24/7.
Fortunately, I stopped using it years ago, and now I wonder why I didn't throw
it out years ago.
Vaughn
Solar Flare
Water is a good conductor of electricity unless it is absolutely pure.
The method used is pulsed water so there is no continuous path betwwen the
500kV line and the nozzle being held by the technician. They aren't "fire
hoses"
"Neon John" <n...@never.com> wrote in message
news:dagc645s4okbmliji...@4ax.com...
z
news:SMydneW3mK1NFPTV...@golden.net:
> Better rethink that washing down 500kV insulators again.
>
> Water is a good conductor of electricity unless it is absolutely pure.
>
> The method used is pulsed water so there is no continuous path betwwen
> the 500kV line and the nozzle being held by the technician. They
> aren't "fire hoses"
I've often wondered about 'wet water' -- its an additive we used in the
tanks. It kept the water from evaporating quite as fast and it would
stick and hold to plants better. Don't know if it made a huge difference
-- I think it was almost like a dishwashing liquid but no bubbles.
Wonder if current would travel through that better.
Always made me paranoid fighting fires around power lines. Some of those
large tower ones would glow red at night and begin stretching. Thats
when you had to boogie cos if they broke you'd get some nasty backlash
Cydrome Leader
I just ran a test similar to the other fellow here.
by ramping up from 0 to 100, 110 and 120 volts with an autotransformer I
measured the VA, current and watts needed to excite modern 10kVA
distribution transformer by back feeding the secondary.
Transfomer was 10kVA, aluminum wound, 3.6% impedance.
current, watt and VA readings were taken off a killawatt meter connected
to the autotransformer. As cheap as these things are, they're pretty
close.
volts fed excitiation VA Watts
to transformer current
=============================================
100 0.27 27 27
110 0.33 36 31
120 0.89 94 41
I never noticed this, but the power factor starts to drop like crazy as
the input approaches 120V. The numbers are a bit off, probably because my
line voltage fluctuates enough to make a difference between the time it
takes to hit buttons on the killawatt.
This is about as small as they come these days in distribution
transfomers. Even if you could magically soft start a transformer like
this, with a 250VA source, you aren't going to be able to do anything, and
that assumes nothing else at all is connected but a transformer a few feet
away.
Bruce Harvey
"Solar Flare" <solar...@hotmale.invalid> wrote in message
news:SMydneW3mK1NFPTV...@golden.net...
> Better rethink that washing down 500kV insulators again.
>
> Water is a good conductor of electricity unless it is absolutely pure.
>
> The method used is pulsed water so there is no continuous path betwwen the
> 500kV line and the nozzle being held by the technician. They aren't "fire
> hoses"
I visited my brother in Canada a few years ago and he said the method that
they use in some areas in North America is to adapt a fire fighting
helicopter with a high pressure washer pump and then hose down the
insulators and lines with water to remove crud build up and ice during
blizzards and ice storms. Apparently as long as they stay above the height
of the power lines there is no risk of grounding the electricity via the
helicopter.
I am told it works very effectively with a relatively small amount of water.
Don Kelly
"Bruce Harvey" <bl.h...@bigpond.com> wrote in message
news:00iak.16187$IK1....@news-server.bigpond.net.au...
>
> "Solar Flare" <solar...@hotmale.invalid> wrote in message
> news:SMydneW3mK1NFPTV...@golden.net...
>> Better rethink that washing down 500kV insulators again.
>>
>> Water is a good conductor of electricity unless it is absolutely pure.
>>
>> The method used is pulsed water so there is no continuous path betwwen
>> the 500kV line and the nozzle being held by the technician. They aren't
>> "fire hoses"
>
> I visited my brother in Canada a few years ago and he said the method that
> they use in some areas in North America is to adapt a fire fighting
> helicopter with a high pressure washer pump and then hose down the
> insulators and lines with water to remove crud build up and ice during
> blizzards and ice storms. Apparently as long as they stay above the height
> of the power lines there is no risk of grounding the electricity via the
> helicopter.
> I am told it works very effectively with a relatively small amount of
> water.
Live line washing and conductance is related to water droplet size. It is
not a new procedure.
--
Don Kelly dh...@shawcross.ca
remove the X to answer
>
>>
>>
>>
Neon John
>"Solar Flare" <solar...@hotmale.invalid> wrote in
>news:SMydneW3mK1NFPTV...@golden.net:
>
>> Better rethink that washing down 500kV insulators again.
>>
>> Water is a good conductor of electricity unless it is absolutely pure.
>>
>> The method used is pulsed water so there is no continuous path betwwen
>> the 500kV line and the nozzle being held by the technician. They
>> aren't "fire hoses"
boy, you sure could have fooled me when I was standing out there helping hold
one! The hose ran right over to a cabinet with the big letters "FIRE" on the
side of it.
Solar fart strikes again...
>
>I've often wondered about 'wet water' -- its an additive we used in the
>tanks. It kept the water from evaporating quite as fast and it would
>stick and hold to plants better. Don't know if it made a huge difference
>-- I think it was almost like a dishwashing liquid but no bubbles.
>
>Wonder if current would travel through that better.
Probably not enough difference to matter. The fire system at a typical plant
takes its feed from "service water". That is, strained (to remove the big
chunks) river water.
>
>Always made me paranoid fighting fires around power lines. Some of those
>large tower ones would glow red at night and begin stretching. Thats
>when you had to boogie cos if they broke you'd get some nasty backlash
Good plan. I'd have been right behind you!
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
You have a magnetic personality... That must be why all your mental floppies are blank.
We Can Do It
"Cydrome Leader" <pres...@MUNGEpanix.com> wrote in message
>
> by ramping up from 0 to 100, 110 and 120 volts with an
> autotransformer I
> measured the VA, current and watts needed to excite modern
> 10kVA
> distribution transformer by back feeding the secondary.
>
> Transfomer was 10kVA, aluminum wound, 3.6% impedance.
>
> current, watt and VA readings were taken off a killawatt
> meter connected
> to the autotransformer. As cheap as these things are,
> they're pretty
> close.
>
> volts fed excitiation VA Watts
> to transformer current
> =============================================
> 100 0.27 27 27
> 110 0.33 36 31
> 120 0.89 94 41
What exactly are these numbers?
With 100 volts backfed into the 120 Volt side one phase to
ground are you saying the Killawatt measured
.27 VA
27 amps
27 watts????????????????????
Was there 10,000 volts on the power line side with the
conductors open.
What happens if the lineman touches the house side of the poll
pig while you are backfeeding it.
peace
dawg
Cydrome Leader
>
> "Cydrome Leader" <pres...@MUNGEpanix.com> wrote in message
> news:g4c85v$d52$> I just ran a test similar to the other
> fellow here.
>>
>> by ramping up from 0 to 100, 110 and 120 volts with an
>> autotransformer I
>> measured the VA, current and watts needed to excite modern
>> 10kVA
>> distribution transformer by back feeding the secondary.
>>
>> Transfomer was 10kVA, aluminum wound, 3.6% impedance.
>>
>> current, watt and VA readings were taken off a killawatt
>> meter connected
>> to the autotransformer. As cheap as these things are,
>> they're pretty
>> close.
>>
>> volts fed excitiation VA Watts
>> to transformer current
>> =============================================
>> 100 0.27 27 27
>> 110 0.33 36 31
>> 120 0.89 94 41
>
> What exactly are these numbers?
It's a text table of numbers. If you set your newsreader to correctly use
monospaced fonts, it will be easier to read.
left column is voltage being backfed into the transformer
column 2 is excitation current of the transformer running no load
column 3 is how many VA are being used
column 4 is how many watts the transformer uses idling.
Voltage one the primary of this transformer with secondary at 120 is about
14.4kV, with no load attached.
The point of all this is, a wimpy distrubution transormer can use about
100VA doing nothing. that number will jump once you have anything
connected to it. a 250VA inverter (if it's even accurately rated) isn't
going to be able to run that thing.
> What happens if the lineman touches the house side of the poll
> pig while you are backfeeding it.
nothing.
BobG
> The point of all this is, a wimpy distrubution transormer can use about
> 100VA doing nothing. that number will jump once you have anything
> connected to it. a 250VA inverter (if it's even accurately rated) isn't
> going to be able to run that thing.
Well crap. Assuming my little PV system isnt going to make the
neighborhood greener by sharing my 250 watts, will it slow my meter
down on its way up the pole to the transformer?
daestrom
If you're using 250 watts or more, then *yes*. Your unit will supply 250
watts of that load and the grid will supply 250 watts less than it would
otherwise. That means over a four hour period, you'll use 1 kWh less of
grid supplied power than you would have otherwise (your meter will register
1 kWh less too).
Every little bit helps ;-)
Just don't expect to save the neighborhood during a power outage :-)
daestrom
Don Kelly
"Cydrome Leader" <pres...@MUNGEpanix.com> wrote in message
The data is questionable as to whether there is meaningful accuracy of the
meter at low currents and low power factors as would be the case for
exciting this transformer (unity pf at 100V??? and 94VA at 120V,0.89A,
but the conclusion that the inverter isn't going to do much is correct.
However, having excited the transformer, there will be potential on the high
side and sufficient reserve capacity of the inverter to deliver a
noticeable (not nothing), but not normally lethal, shock to anyone in
contact with the high side. Of course if the linesman follows proper
procedure, he wouldn't get a shock but the inverter could be toast.
Cydrome Leader
The PF at 100 volts is strange, and why I even bothered to post it here. I
wonder if it has to do with the possibly high capacitance of the primary
winding and some automatic power factor correction because of this.
Considering a 14.4kV 200kVAR power factor correction cap is only about
2.6uF or something close to that, it doesn't seem that unlikely that x nF
of parasitic capacitance in the primary winding/tank/insulators can
correct a couple dozen (if even) VA.
Neon John
>-------------
>The data is questionable as to whether there is meaningful accuracy of the
>meter at low currents and low power factors as would be the case for
>exciting this transformer (unity pf at 100V??? and 94VA at 120V,0.89A,
Not really. AT that low excitation level, hysteresis in the core or plain old
dissipation in the high voltage dielectric could account for the high pf. I'd
lean toward dielectric dissipation.
>but the conclusion that the inverter isn't going to do much is correct.
>However, having excited the transformer, there will be potential on the high
>side and sufficient reserve capacity of the inverter to deliver a
>noticeable (not nothing), but not normally lethal, shock to anyone in
>contact with the high side. Of course if the linesman follows proper
>procedure, he wouldn't get a shock but the inverter could be toast.
Nah, the inverter will simply shut down, like it does when presented with any
other short. But you touch on another are where the safety idiots are running
on blind ignorance.
First a little math.
250 watts at 14,400 volts (a common distribution voltage) is 0.017 amps or 17
ma. That's assuming that the pig is 100% efficient and that the inverter can
actually power up the pig, two things that we know are not true. But let's
pretend.
Consider 17ma. Automotive ignition systems produce more current than that.
Oil burner ignition transformers are typically 20 ma. Neon sign transformers
are commonly 30, 60 or 120 ma at up to 15,000 volts. Literally thousands of
people a day get zapped from all of these sources and have little to show for
it other than a sheepish grin and maybe wet underwear. As a neonist, I've had
my share of "illuminating" experiences at the hands of neon transformers. I'd
rather not experience that ever again but OTOH, I'm not going to cower in the
corner in fear of a few ma of high voltage current.
<we shall now pause for a moment for the safety panty wetters to quote how
much current through the heart it takes to kill, yada yada yada. Then we take
another moment to observe that the current has to get to the heart before it
can do anything. There's a reason why defibrillators dump 400 joules or more
of energy and literally amps of current into the paddles and it ain't to help
send big capacitor manufacturers' kids through college.>
This whole thread was born of ignorance and perpetuated by the petty
authoritarians who don't actually have any technical learning but who want to
tell others what to do anyway. Such a waste of time.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Unable to locate Coffee -- Operator Halted!
nicks...@ece.villanova.edu
>OK, now the cool totally improper method.
>Kids don't do this without adult supervision.
>You don't need to be synchronous with the grid in
>any way to send power back to the grid.
>
>I did some experiments to learn about grid tie
>techniques. I used a high end Yokogawa AC power
>meter and a high power current source. I also
>had a conventional mechanical KWHr meter. ( disk
>type.)
>
>This was connected to the grid and supplied with
>an AC power source. The source was a 100kW
>Pacific Power electronic amplifier designed to
>power our computer for compliance tests.
>
>This amplifier is essentially a huge power
>amplifier capable of out AC, DC, and any other
>wave shape including square waves at up to about
>280 volts.
>
>I injected current into the grid through the
>power meter. I could vary the frequency and
>wave shape up to about 800Hz and directed the
>power meter and KWHr to measure the power and
>direction of flow.
>
>I injected the current and showed that power
>always flowed to the grid. No mater what the
>phase, frequency, voltage or wave shape was.
>
>Further, the mechanical power meter performed
>correctly and successfully measured the power and
>directly. At least up until higher frequencies
>above 500Hz
Sounds great :-) What's the least-expensive way to do this?
Nick
Solar Flare
dreaming that one.
"Don Kelly" <dh...@shaw.ca> wrote in message
news:5siak.41823$kx.14983@pd7urf3no...
daestrom
> It isn't a new procedure and they don't use a fire hose. Somebody was
> dreaming that one.
>
I think Neon John started that, but I have to agree with him. Watched them
do it in the San Francisco bay area where sea salt is a problem. But I
can't remember if they killed power to the line first, or did it 'live'.
That was a *few* years back.
daestrom
Solar Flare
They do it live for the voltages up to 27kV, I have watched, here.
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:g5125...@news2.newsguy.com...
rdaig...@gmail.com
wrote:
> "Richard P." <n...@home.eh> wrote in message
>
> news:r__6k.15614$kx.12206@pd7urf3no...
>
> > Maury, there is this item that may answer your question:
> >http://www.buyerisland.net/greenpower.htm
>
> Bingo! Give that man the prize.
>
> Vaughn
Or check out the SWEA inverter. It is completely what you are after.
It is compliant in many countries and growing all the time. I am the
Aussie/NZ distributor. www.laddertech.com.au, there is a link to Swea
there.
Vaughn Simon
<rdaig...@gmail.com> wrote in message
news:9c48ce7b-bc74-47d2...@d19g2000prm.googlegroups.com...
> Or check out the SWEA inverter. It is completely what you are after.
> It is compliant in many countries and growing all the time. I am the
> Aussie/NZ distributor. www.laddertech.com.au, there is a link to Swea
> there.
Thanks for bringing that to our attention! That said, I don't think that it
does exactly what the OP was looking for since he wanted something that would
run from a single 18 volt panel. The SWEA seems to require higher voltage than
that. (assuming that I found the correct product...did I?)
It is nice that someone is making this stuff. I am honestly tempted to give
it a go myself just for the helluvit, but I would never be able to confess to my
wife what the system really cost vs. how trivial the payback would be. I would
especially never be able to explain to her why the system would contribute
nothing to our energy needs following a hurricane.
Vaughn
rdaig...@gmail.com
<vaughnsimonHATESS...@att.FAKE.net> wrote:
> <rdaigna...@gmail.com> wrote in message
Hi Vaughn, I wish I could design up devices like this.
This will accept single 18 volts input. The unit is settable for most
situations upto 55 volts input. Works, well and is very simple to
use.
It is best not to discuss paybacks. Does anyone calculate the payback
on their LCD widescreen or dishwasher?
This is a great thread.
Ralph