Do AC power tools have DC motors?
Da Man
not have speed control, as a TRIAC is basically a SCR that works both ways.
"DaveC" <an...@example.net> wrote in message
news:01HW.B7790DA50...@news.dnai.com...
> Milwaukee, Hitachi, etc. Sawzall, power drills, etc. that are AC powered
and
> have variable speed control via trigger control, do these rectify the AC
and
> use DC motors? Or do they use SCR to control speed?
>
> Always wondered, never discovered.
> --
> Note that my return address is corrupted in an attempt to reduce spam. If
you
> choose to e-mail me, please correct my address as described below.
>
> Thanks,
> Dave
> ---
> Dave Carpenter
> Sound Logic
> voic...@NOdnai.com
>
> Remove "NO" to reply via e-mail
>
Mike Page
news:01HW.B7790DA50...@news.dnai.com...
> Milwaukee, Hitachi, etc. Sawzall, power drills, etc. that are AC powered
and
> have variable speed control via trigger control, do these rectify the AC
and
> use DC motors? Or do they use SCR to control speed?
>
> Always wondered, never discovered.
> --
> Note that my return address is corrupted in an attempt to reduce spam. If
you
> choose to e-mail me, please correct my address as described below.
>
> Thanks,
> Dave
> ---
> Dave Carpenter
> Sound Logic
> voic...@NOdnai.com
>
> Remove "NO" to reply via e-mail
I would imagine they are DC, using SCR then rectifier to deliver a variable
DC voltage. Hence the brushes and sparks (and smell). Induction motor speed
control requires more electronics. Some time there will be a crossover,
because induction motors are cheaper.
Best Regards,
Mike.
***********************************************************************
Mike Page BEng (hons) AMIEE mi...@buckman-hardy.co.uk
Senior Design Engineer http://www.buckman-hardy.co.uk
Buckman Hardy Associates Tel +44 1304 365918 Fax +44 1304 369737
***********************************************************************
John Woodgate
inimitably wrote:
>Milwaukee, Hitachi, etc. Sawzall, power drills, etc. that are AC powered and
>have variable speed control via trigger control, do these rectify the AC and
>use DC motors? Or do they use SCR to control speed?
They do (at least those made for Europe prior to this year) effectively
rectify the AC, but only below maximum speed, because they use
asymmetrical phase-control of speed with a thyristor/SCR, not a triac.
The motors are AC commutator motors, which you won't find described in
most textbooks, but are made and used in many millions.
I know, because I've looked at the current waveform, after someone
questioned whether they meet EN61000-3-2. They may do, because
asymmetrical control is allowed for motor speed control of Class II
portable equipment (clause 6.1 c) and text following, of
EN61000-3-2:2000). But whether they meet the applicable Class B limits
is another matter.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
This message and its contents are not confidential, privileged or protected
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The contents may be disclosed to, or used by, anyone and stored or copied in
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yesterday at the latest.
Mark Kinsler
>have variable speed control via trigger control, do these rectify the AC and
>use DC motors? Or do they use SCR to control speed?
>
Like the man said, they're universal motors. They're wound-rotor,
brush-type motors, typically with the field and armature connected in
series. Such a motor will run well on either AC or DC because the
magnetic field in the stator and the magnetic field from the rotor
will be reversed simultaneously with AC. The series connection of the
rotor and stator provides high starting torque. Induction motors
aren't used because it's difficult to provide sufficient starting
torque, especially in a motor of small physical size.
The triac controls the motor's speed by reducing the input voltage to
zero for a variable portion of each half-cycle, but the current
through the motor is bi-directional. Any rectification scheme would
drastically reduce the motor's power. I believe that most power
tools would run on DC, but I've never tried it.
M Kinsler
512 E Mulberry St Lancaster Ohio USA 740.687.6368
http://www.frognet.net/~kinsler
liberal
"Mark Kinsler" <kin...@frognet.net> wrote in message
news:3b55b3f0...@news.earthlink.net...
Uh, look at all the battery drill motors and the multitude of battery
operated hand tools guys!
Mark Daniels
<nos...@kscable.com> writes
>
>"Mark Kinsler" <kin...@frognet.net> wrote in message
>news:3b55b3f0...@news.earthlink.net...
>> >Milwaukee, Hitachi, etc. Sawzall, power drills, etc. that are AC powered
>and
>> >have variable speed control via trigger control, do these rectify the AC
>and
>> >use DC motors? Or do they use SCR to control speed?
>> >
>> >Always wondered, never discovered.
>>
>> Like the man said, they're universal motors. They're wound-rotor,
>> brush-type motors, typically with the field and armature connected in
>> series. Such a motor will run well on either AC or DC because the
>> magnetic field in the stator and the magnetic field from the rotor
>> will be reversed simultaneously with AC. The series connection of the
>> rotor and stator provides high starting torque. Induction motors
>> aren't used because it's difficult to provide sufficient starting
>> torque, especially in a motor of small physical size.
Why do you need much starting torque in a power tool? Look at the way in
which most are used: the motor generally runs up to speed before any
appreciable load is put on it. Besides, starting torque for a three
phase motor connected DOL can easily be 2.5 times full load torque. I
appreciate you may have been referring to single phase motors.
I know that Bosch (amongst others) produces three phase drills and
breakers that run from a 400 Hz generator. I also believe that a higher
frequency, higher speed induction motor is being developed specifically
for use in small, portable power tools, now that it is possible to build
inexpensive inverter drives. Not that I said anyone was producing these
drives for a low price at present ;)
>>
>> The triac controls the motor's speed by reducing the input voltage to
>> zero for a variable portion of each half-cycle, but the current
>> through the motor is bi-directional. Any rectification scheme would
>> drastically reduce the motor's power. I believe that most power
>> tools would run on DC, but I've never tried it.
>>
>> M Kinsler
>> 512 E Mulberry St Lancaster Ohio USA 740.687.6368
>> http://www.frognet.net/~kinsler
>
>
>Uh, look at all the battery drill motors and the multitude of battery
>operated hand tools guys!
This doesn't help much, because most of these use permanent magnet
motors. Mark is quite correct and I have actually tried running a power
tool with a universal motor on d.c.
>
>
--
Mark Daniels
Mark Kinsler
>>Uh, look at all the battery drill motors and the multitude of battery
>>operated hand tools guys!
>
>This doesn't help much, because most of these use permanent magnet
>motors. Mark is quite correct and I have actually tried running a power
>tool with a universal motor on d.c.
I don't have an battery-powered drills, etc., but when I've tried them
I noticed that they seem to be fed with either a high-frequency AC or
pulse train. They give out a high-pitched whine when the trigger is
at half-throttle. I suppose that this is an artifact of the speed
control, and I suspect that most of the battery-operated tools used
these days are somewhat more complicated than my beloved seven-dollar
Wal-mart rechargeable screwdriver.
Don Kelly
--
Don Kelly
dh...@homebody.com
remove the corpse to answer
"DaveC" <an...@example.net> wrote in message
news:01HW.B77B98FC0...@news.dnai.com...
> How does this AC-powered tool motor revese? There's a forward/reverse
switch
> in the handle, and the best I can see, it reverses the winding relative to
> the brushes (armature). This reverses the relative magnetic fields and
> reverses direction? Is that all there is to it?
Paul Perry
stripping heat gun which failed for no apparent reason after only 6
hours of use.
I see an open-circuit 1N5398 diode going from mains to the tiny motor.
Is it usual for a diode like this to fail open-circuit?
-paul perry Melbourne Australia
John Gilmer
> On Thu, 19 Jul 2001 7:15:31 -0700, AC/DCdude17 wrote
> (in message <3B56EB82...@gNOSPAMay.com>):
>
> >> Not with a number of uses like drilling/jammed bits, or as a
screwdriver
> >> etc.
> >
> > Portable tools are subjected to such use more than AC tools are. AC
> > drills are good drills, but many consumer AC drills don't have the
> > torque to be used as a screwdriver.
>
> In the construction industry, battery-powered tools, with the exception of
> the venerable drill/driver (ie, DeWalt, Makita, etc.), are seen as
laughable.
> Power, durability, longevity are completely absent. We're talking about
> *real* AC power tools (ie, Milwaukee, etc.), not consumer-grade Home Depot
> stuff.
Heck, any ac powered 3/8" or large electric drill can just about twist the
head off of most deck screws. The electric screw drivers are a JOKE.
But any ac powered drill with the proper bit will do a fine job driving
screws.
John Gilmer
> On Thu, 19 Jul 2001 9:18:03 -0700, John Gilmer wrote
> (in message <3b57095d$0$22...@dingus.crosslink.net>):
>
> > The electric screw drivers are a JOKE.
>
etc.).
> Even driving small screws into wood will stall it. But many electricians
use
> them to speed removing cover plate screws and other time-consuming jobs
that
> can wear out your wrist. For light-duty, repetitive tasks, they're a
godsend.
Even for that function the pro electrician I know uses a battery powered
3/8" drill. Just about all have them have an adjustable clutch that will
limit the torque you put on the screw.
Since you need a drill for drillng holes anyway there just isn't much use
for the electric screwdriver. I had one for awhile and when it broke I
never replaced it. If I got one as a gift I would re-wrap it and give it
to someone else.
Rod Speed
AC/DCdude17 <bi_t...@gNOSPAMay.com> wrote in
message <3B56EB82...@gNOSPAMay.com>
> Rod Speed rod_...@yahoo.com wrote
>> Mark Daniels <j...@third-millennium.demon.co.uk> wrote
>>>>>> Milwaukee, Hitachi, etc. Sawzall, power drills, etc.
>>>>>> that are AC powered and have variable speed control
>>>>>> via trigger control, do these rectify the AC and use
>>>>>> DC motors? Or do they use SCR to control speed?
>>>>>> Always wondered, never discovered.
>>>>> Like the man said, they're universal motors. They're wound-rotor,
>>>>> brush-type motors, typically with the field and armature connected
>>>>> in series. Such a motor will run well on either AC or DC because
>>>>> the magnetic field in the stator and the magnetic field from the rotor
>>>>> will be reversed simultaneously with AC. The series connection
>>>>> of the rotor and stator provides high starting torque. Induction
>>>>> motors aren't used because it's difficult to provide sufficient
>>>>> starting torque, especially in a motor of small physical size.
>>> Why do you need much starting torque in a power tool?
>>> Look at the way in which most are used: the motor generally
>>> runs up to speed before any appreciable load is put on it.
>> Not with a number of uses like drilling/jammed bits, or as a screwdriver etc.
> Portable tools are subjected to such use more than AC tools are.
Nope, not with drilling and jammed bits they arent.
> AC drills are good drills, but many consumer AC drills
> don't have the torque to be used as a screwdriver.
Plenty of the bigger drills do.
repatch
> switch or outlet. Those *slotted* screws (whenever is the manufacturing
world
> going to dump those and go with philips!?!) are difficult to hold a driver
> bit in without slipping off, unless it's a small, light, palm-sized
driver.
I agree with you on slotted screws, but I'll go a step further: when
will manufacturers switch to Robertson? (square). This type of screw is
easily the best available. Once you go Robertson you just can't go back.
TTYL
Spehro Pefhany
> I agree with you on slotted screws, but I'll go a step further: when
> will manufacturers switch to Robertson? (square). This type of screw is
> easily the best available. Once you go Robertson you just can't go back.
> TTYL
I have a fondness for the Robertson screws.. the driver tips are usually
of very high quality.
But if you've looked at toys recently, they have a pseudo-Robertson, I
think called a delta screw that uses a triangular bit. It's probably as
good, all other things being equal.
Best regards,
--
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Spehro Pefhany --"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Contributions invited->The AVR-gcc FAQ is at: http://www.BlueCollarLinux.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
John Woodgate
outside Canada. I can't buy Robertson bits from any easily-accessible
source in UK, even if I wanted some.
Phil Allison
Paul Perry <pfp...@melbpc.org.au> wrote in message
news:defd51b9.01071...@posting.google.com...
> Curiously enough, I'm just looking at a Black&Decker KX1600 paint
> stripping heat gun which failed for no apparent reason after only 6
> hours of use.
> I see an open-circuit 1N5398 diode going from mains to the tiny motor.
> Is it usual for a diode like this to fail open-circuit?
>
Yes, for those that don't fail short-circuit.
Regards, Phil
Dean Huster
speed, all they need to do is reverse the field winding connections
and the motor reverses direction. In a cordless (battery operated)
tool, they have to reverse the wires to the rotor since the field is a
permanent magnet.
Dean
Jerry Greenberg
--
There are some specialized machine tools that use DC motors. The
power is converted to DC from the AC source in order to be used.
These usualy are equipment that would use very precise servo driven
system for their application.
It realy depends on the designer's approach. It is possible however
to make very precise AC driven servos, but the approach is different.
Jerry Greenberg
http://www.zoom-one.com
--
Greg Teets
reverse the wires?? how do they do that?
On 21 Jul 2001 07:39:42 -0700, dhu...@pb.k12.mo.us (Dean Huster)
wrote:
Vic
"Greg Teets" <gte...@rr.cinci.com> wrote in message
news:3b59f90b.241726324@news-server...
> i'm kind of new ...
>
> reverse the wires?? how do they do that?
use a switch.
Mark Daniels
<an...@example.net> writes
>On Fri, 20 Jul 2001 9:18:54 -0700, repatch wrote
>(in message <2LY57.13192$ca3.1...@news20.bellglobal.com>):
>
>>> switch or outlet. Those *slotted* screws (whenever is the manufacturing
>> world
>>> going to dump those and go with philips!?!) are difficult to hold a driver
>>> bit in without slipping off, unless it's a small, light, palm-sized
>> driver.
>>
>> I agree with you on slotted screws, but I'll go a step further: when
>> will manufacturers switch to Robertson? (square). This type of screw is
>> easily the best available. Once you go Robertson you just can't go back.
>> TTYL
>
>to have your torque (clutch) set *just right*. I've snapped off too many of
>those dudes, whereas a Philips (now known as Posidrive) have just slipped
>out.
Sorry, but a Philips is NOT known as a posidrive. These are two
different animals. The posidrive looks a bit like a philips, but has
four extra (smaller) drive points in the design, rotated 45 deg from the
main cross.
>
>"Auto clutch" screws, I call them.
--
Mark Daniels
Don Kelly
chewed up and a quarter inch to go. Give me a Robertson over a Phillips (or
a straight slot) any day.
--
Don Kelly
dh...@homebody.com
remove the corpse to answer
"Mark Daniels" <j...@third-millennium.demon.co.uk> wrote in message
news:PMlkaDAy...@third-millennium.demon.co.uk...
Neil
> I agree that they are very good, but they seem to be almost unknown
> outside Canada. I can't buy Robertson bits from any easily-accessible
> source in UK, even if I wanted some.
> --
How about Screwfix (0500 414141) (screwfix.com) ?
Their D5297-63 is a £9.50 set of bits including "4 x triwing, 4 x square" which
may be what you mean.
They may be able to tell you of supplier of qualtiy (not cheap) ones ...
hth
Neil
ScottBob
banged in:
>They use a TRIAC, and are universal motors. They will run on DC, but will
>not have speed control, as a TRIAC is basically a SCR that works both ways.
I used to work in the tool department at Home Depot and I was fielded
this question a lot. Many welders bought drills, jigsaws and
side-grinders with the intention of plugging them into their engine
driven electric arc welders, which usually have a utility outlet on
them which output 120 volts D.C. for handheld power tools and
incandescent drop-cord lighting. More expensive arc welders can output
AC, but there are a great many older arc welders still in use that
were built before the advent of semiconductor speed controls in power
tools.
I always told those who asked me to look at the label to see if it
says for AC or DC use on it, if it says "AC only" it has a
semiconductor speed control that won't work with DC.
David Emrich
"ScottBob" <re...@here.only> wrote in message
news:0jbqltge8duuhh882...@4ax.com...
> On Tue, 17 Jul 2001 02:33:55 -0300, "Da Man" <levy...@hotmail.com>
> banged in:
>
> >They use a TRIAC, and are universal motors. They will run on DC, but will
> >not have speed control, as a TRIAC is basically a SCR that works both
ways.
>
[snip]
> I always told those who asked me to look at the label to see if it
> says for AC or DC use on it, if it says "AC only" it has a
> semiconductor speed control that won't work with DC.
There appear to be three classes of "problem" here:
1. A truly AC only motor (eg, induction type) will likely fry itself if
powered on DC since it relies on the current being out of phase with the
voltage to limit the power dissipation in the windings. Feed it with DC and
all you've got is the wire resistance dissipating all that electricity
coming in as heat.
2. A motor that's universal (ie, doesn't care about AC or DC as far as the
motor itself) but has a triac on it will work "sort of" on DC except that
it'll run to full speed once you press the trigger even a little bit, and it
won't stop unless you pull the plug. Not recommended on safety grounds, but
at least it shouldn't fry itself.
3. A bare universal motor (no triac speed control) with a regular on-off
switch will work happily on AC or DC (within nameplate ratings of course).
Phil Allison
David Emrich <dem...@ihgtech.com.au> wrote in message
news:9jjeg6$rdm$1...@yeppa.connect.com.au...
> 1. A truly AC only motor (eg, induction type) will likely fry itself if
> powered on DC since it relies on the current being out of phase with the
> voltage to limit the power dissipation in the windings.
An induction motor will not rotate if fed DC, just lock up and burn.
I have recently checked a couple of domestic fans and found the phase angle
is very small, no more than 20 degrees. At medium speed the angle was almost
zero. However, the DC resistance is several times lower than the AC current
draw would suggest.
I have read that synchronous motors can be designed to have almost any phase
angle, even look capacitive so they can be used for power factor correction.
Regards, Phil
Don Kelly
"David Emrich" <dem...@ihgtech.com.au> wrote in message
news:9jjeg6$rdm$1...@yeppa.connect.com.au...
>
> There appear to be three classes of "problem" here:
>
> 1. A truly AC only motor (eg, induction type) will likely fry itself if
> powered on DC since it relies on the current being out of phase with the
> voltage to limit the power dissipation in the windings. Feed it with DC
and
> all you've got is the wire resistance dissipating all that electricity
> coming in as heat.
------------
1) is true in that the motor will fry itself. However, the induction motor
does not depend on the current being out of phase with the voltage either
to limit power dissipation or in its operation. The main power dissipation
is an I^2*R loss which depends on current magnitude not phase or voltage.
Consider the induction motor as a transformer (with a moving secondary -
primary doesnt "know" that secondary is moving) - which doesn't work on DC
-------------------
>
> 2. A motor that's universal (ie, doesn't care about AC or DC as far as the
> motor itself) but has a triac on it will work "sort of" on DC except that
> it'll run to full speed once you press the trigger even a little bit, and
it
> won't stop unless you pull the plug. Not recommended on safety grounds,
but
> at least it shouldn't fry itself.
>
> 3. A bare universal motor (no triac speed control) with a regular on-off
> switch will work happily on AC or DC (within nameplate ratings of course).
-------------------------------
Other comments (2,3) are fine but note that a "bare" universal motor will
actually work a bit better on DC than on AC.
Don Kelly
that they can be inductive(underexcited) or capacitive (overexcited). Power
factor compensation with synchronous machines is a common practice.
"Phil Allison" <bi...@bigpond.com> wrote in message
news:Wsc77.13109$a04....@newsfeeds.bigpond.com...
William Gleason
only D.C. is at the end of the welding electrode. Logic says: Why convert A.C.
to D.C if you don't have to...? rectifiers are expensive and the 15 / 20 Amp.
ones are very expensive. D.C. generator welders, different animal...
Terry S
William Gleason wrote:
>
> I have repaired welders for years and if the welder plugs into the wall, the
> only D.C. is at the end of the welding electrode. Logic says: Why convert A.C.
> to D.C if you don't have to...? rectifiers are expensive and the 15 / 20 Amp.
> ones are very expensive. D.C. generator welders, different animal...
>
The wording was
> > Many welders bought drills, jigsaws and
> > side-grinders with the intention of plugging them into their ................. "engine
> > driven" .................... electric arc welders, which usually have a utility outlet on
> > them which output 120 volts D.C.
Not AC operated ones I gather! Reminds me that we sold some
ex-telepphone company DC generators (48 volt 200 amp etc. that were
bought by a welding company!
BTW what is the normal voltage and frequency 'down under'?
Is it 50 or 60 hertz? Probably 50 eh?
Domestic voltage is? Probably 230 volts. Live wire and neutral plus
ground into domestic premises????
Be interested to know! TIA.
Terry Esastern Canada.
Rod Speed
Terry S <tsan...@nf.sympatico.ca> wrote in message news:3B794DAD...@nf.sympatico.ca...
> BTW what is the normal voltage and frequency 'down under'?
The freq is 50Hz.
The voltage is much more variable. Nominally 240V in much
of the country but not all, some parts were as much as 260V.
And that detail has changed in recent times with an attempt to make
it more uniform countrywide, mainly by dropping the highest nominals.
> Is it 50 or 60 hertz? Probably 50 eh?
Yep.
> Domestic voltage is? Probably 230 volts.
Nope, its not normally that low, particularly the nominal.
> Live wire and neutral plus ground into domestic premises????
Nope, grounded at each domestic premises.
Technically the MENS system. Multiple earthed neutral.
Modern houses are usually single phase, some with off
peak mains appliances are 2 phase, 3 phase only where
that can be justified by the need for 3 phase equipment.
Older houses are often 3 phase. Older in the sense of say 50 years or more.
Don Kelly
it is often called a universal motor. Why use it- fairly cheap and simple
and lighter, with a possible higher speed than an induction motor(fastest is
3000rpm at 50Hz). Originally resistor control was used (and these would
work quite well with DC) but triac control is more efficient. Now many use
a permanent magnet DC shunt motor which has the advantage of more constant
speed under load. These will use SCR's or diodes. The cost of the
electronics involved is relatively small for these applications- the
manufacturer is buying them by the thousands. The choice between such a
motor and an inductionmotor in larger sizes depends on the application-
speed, portability, weight, etc.
--
Don Kelly
dh...@homebody.com
remove the corpse to answer
"William Gleason" <william...@kodak.com> wrote in message
news:3B794557...@kodak.com...
John Beardmore
<william...@kodak.com> writes
>I have repaired welders for years and if the welder plugs into the wall, the
>only D.C. is at the end of the welding electrode. Logic says: Why convert A.C.
>to D.C if you don't have to...? rectifiers are expensive and the 15 / 20 Amp.
>ones are very expensive.
Because you can do better welds in steel with DC.
Aluminium on the other hand requires AC.
Cheers, J/.
--
John Beardmore
John
DC to weld with. Some processes require DC (Mig, for instance) and in
others there are distinct advantages to DC for some work and in AC for
other- Stick and Tig both have applications where either AC or DC will
be preferred. You go farther, and you'll get into processes that use
both at the same time- DC for the main arc and AC to preheat the
additional filler wire.
Re; Motors in power tools and DC- Most all modern power tools use a
universal type motor, which will operate on DC or AC to 60 or so
cycles. The switch is another thing- the triac switches will fail in a
remarkably short time when used on DC, once they go on they stay on,
no zero point to allow them to go off, so there's no speed control, as
in a VSR drill and even switches in cheap circular saws are triac
controlled and the DC will kill them too. Been there a couple of
times. Used to be, if it was a universal motor it wouldn't matter if
the label said anything about DC or not- it was OK. Not that way
anymore, pays to be sure beforehand.
John
Terry S
Wow up to 260 volts!
I didn't word that 'wire into domestic premises' question very well but
OK. The ground (earth) sounds very much what we call 'Multi grounded
neutral' can't recall what the UK equivalent is called.
Typically here, three wires come into the house from the distribution
transformer. They are, as it were
Plus 115 volts live.
Zero neutral
Minus 115 volts live.
So there is 230 volts between the two outer 'legs', to which we connect
heavier items such as water heaters using two pole circuit breakers.
This comes from a centre tapped 230 volt secondary of the electric
utilities 'distribution' transformer which in most case is pole mounted.
In normal installations here the zero neutral wire is grounded at the
transformer and grounded again at the house by means of ground rod and
connection to grounded water pipes. Most of our distribution is aerial
and the neutrals of both the secondary and primary systems are connected
to everything else in site that is grounded. This includes many pole guy
wires, telephone and cable television support cable sheaths etc. The
primary distribution voltages are typically about 13-14 Kv.
We bought an electric cooking stove that had been in Australia; and
found inside a centre tapped auto transformer which appears to be
capable of around 500 watts. from the way it was wired we figured that
it's purpose was to provide a 115 volt centre tap for the items on the
stove that used 115, such as the oven light, top light etc. the timer
clock would have been slow on 50 hertz but the 60 hertz clock circuit
was connected!
Thanks for the posting and the info.
Terry Eastern Canada.
Rod Speed
Terry S <tsan...@nf.sympatico.ca> wrote in message news:3B7D6B9C...@nf.sympatico.ca...
>>> BTW what is the normal voltage and frequency 'down under'?
>> The freq is 50Hz.
>> The voltage is much more variable. Nominally 240V in much
>> of the country but not all, some parts were as much as 260V.
>> And that detail has changed in recent times with an attempt to make
>> it more uniform countrywide, mainly by dropping the highest nominals.
>>> Is it 50 or 60 hertz? Probably 50 eh?
>> Yep.
>>> Domestic voltage is? Probably 230 volts.
>> Nope, its not normally that low, particularly the nominal.
>>> Live wire and neutral plus ground into domestic premises????
>> Nope, grounded at each domestic premises.
>> Technically the MENS system. Multiple earthed neutral.
>> Modern houses are usually single phase, some with off
>> peak mains appliances are 2 phase, 3 phase only where
>> that can be justified by the need for 3 phase equipment.
>> Older houses are often 3 phase. Older in the sense of say 50 years or more.
> Wow up to 260 volts!
Yeah, thats the main reason it got chopped back in recent years,
thats getting a bit on the high side, particularly with imported
220V stuff that became much more common in recent times.
> I didn't word that 'wire into domestic premises' question very well but OK.
> The ground (earth) sounds very much what we call 'Multi grounded neutral'
Yep.
> can't recall what the UK equivalent is called.
Yeah, I cant either.
> Typically here, three wires come into the house from
> the distribution transformer. They are, as it were
> Plus 115 volts live.
> Zero neutral
> Minus 115 volts live.
> So there is 230 volts between the two outer 'legs', to which we connect
> heavier items such as water heaters using two pole circuit breakers.
> This comes from a centre tapped 230 volt secondary of the electric
> utilities 'distribution' transformer which in most case is pole mounted.
Yeah, we have never done it like that. Its the main thing it
takes us a while to grasp about the north american system.
We still have a bit of single wire stuff, usually called SWER, single wire
earth return. Only seen in rural areas for power more isolated propertys.
Looks weird when you look at the poles.
> In normal installations here the zero neutral wire is grounded at the
> transformer and grounded again at the house by means of ground
> rod and connection to grounded water pipes. Most of our distribution
> is aerial and the neutrals of both the secondary and primary systems
> are connected to everything else in site that is grounded. This includes
> many pole guy wires, telephone and cable television support cable
> sheaths etc. The primary distribution voltages are typically about 13-14 Kv.
Yeah, ours is mostly 11KV down residential streets, usually 3
wires on the top of the poles in a triangular config, with 4 wires
of the 240/415 in a horizontal line lower down the pole. Obviously
the 11KV primary distribution is only on some of the runs of poles.
> We bought an electric cooking stove that had been in Australia; and
> found inside a centre tapped auto transformer which appears to be
> capable of around 500 watts. from the way it was wired we figured
> that it's purpose was to provide a 115 volt centre tap for the items
> on the stove that used 115, such as the oven light, top light etc.
It must have been something unusual, like from north america
originally. Ours just have 240V devices, lights, elements etc.
> the timer clock would have been slow on 50 hertz
> but the 60 hertz clock circuit was connected!
> Thanks for the posting and the info.
No problem, I find that sort of thing quite interesting.
> Terry Eastern Canada.
Duane Bozarth
SWER...I've also seen it in the prairie provinces of Canada...
John Woodgate
wrote (in <3B7D6B9C...@nf.sympatico.ca>) about 'Do AC power tools
have DC motors?', on Fri, 17 Aug 2001:
>The ground (earth) sounds very much what we call 'Multi grounded
>neutral' can't recall what the UK equivalent is called.
PME -Protective Multiple Earthing. Only used when a low impedance earth
loop cannot be provided with separate neutral and protective conductors
right back to the distribution transformer, which may in rural areas be
several kilometres away. The neutral is normally earthed only at the
transformer.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Eat mink and be dreary!
Rod Speed
Duane Bozarth <dp_bo...@swko.dot.net> wrote in
message news:3B7DCF08...@swko.dot.net...
> There are still a <few> areas in very rural US that also have
> SWER...I've also seen it in the prairie provinces of Canada...
Yeah, guess the same economic rationale applys.
Forget what voltage it runs at here.
>> Terry S <tsan...@nf.sympatico.ca> wrote
Daniel Narvaes
Vic wrote in message ...
trash
IT depends on what type of AC motor it is.
If it's a traction motor, then you'd reverse the field coil,
and leave the stator the same way.
In 3 phase motors you just swap two of the phases.
In most AC motors it's the phase of the current in relation
to other parts of the motor. Think of a railway pump wagon.
Both sides push and pull, it's only their phase in relation to the wheels
which determines which way the wagon goes.
trash0 @ cannabismail . com
he...@mbox.com.au
Australia's #1 spam company
goldenpi
trash <trash0@hotmail..com> wrote in message
news:3b8c7026.6729847@news-server...
Reverse the field coil, or use a gearbox.
AC power tools need a gearbox to lower the speed and increase torque. Often
they also reverse the tool.
Lane Lewis
tools) Induction motors do it differently (drill presses).
Lane
"Daniel Narvaes" <dnar...@vigoris.net> wrote in message
news:3b61...@news.vigoris.net...
Oppie
armature and reverse it.
sno...@seashell.sasquatch.com
Might be difficult to do with brushes at one end. :-)
Stan
Andrew
>... or if it is a double shaft motor, use the other side. or remove the
>armature and reverse it.
>
Or maybe you could just flick the reverse switch (provided it has
one!).
ISO-teric
ISO-teric
Jason
an idea of what sort of motor it is, and then tell you how to reverse it.
Jason
"Lane Lewis" <lanjl...@earthlink.net> wrote in message
news:IRnj7.6493$Fv3.5...@newsread2.prod.itd.earthlink.net...
goldenpi
4 terminals - bi-directional ac
more than 4 wires - stepper, shouldn't be in a power tool.
Jason <sjmar...@optusnet.com.au> wrote in message
news:3b906f86$0$20903$7f31...@news01.syd.optusnet.com.au...
Mark Daniels
<gold...@crosswinds.net> writes
>2 terminals - dc ot one-directional ac.
>4 terminals - bi-directional ac
>more than 4 wires - stepper, shouldn't be in a power tool.
>
>Jason <sjmar...@optusnet.com.au> wrote in message
>news:3b906f86$0$20903$7f31...@news01.syd.optusnet.com.au...
>> You have to be more specific as to what the motor is in for someone to
>have
>> an idea of what sort of motor it is, and then tell you how to reverse it.
>>
>> Jason
>>
>> "Lane Lewis" <lanjl...@earthlink.net> wrote in message
>> news:IRnj7.6493$Fv3.5...@newsread2.prod.itd.earthlink.net...
>> > You should be able to find a schematic on an armature type ac
>motor.(hand
>> > tools) Induction motors do it differently (drill presses).
>> >
>> > Lane
>> >
>> > "Daniel Narvaes" <dnar...@vigoris.net> wrote in message
>> > news:3b61...@news.vigoris.net...
>> > >
>> > > Vic wrote in message ...
>> > > >
>> > > >"Greg Teets" <gte...@rr.cinci.com> wrote in message
>> > > >news:3b59f90b.241726324@news-server...
>> > > >> i'm kind of new ...
>> > > >>
>> > > >> reverse the wires?? how do they do that?
>> > > >
>> > > >use a switch.
>> > > >
>> > > Specifically, a DPDT switch.
>> > >
>> > >
>> > >
>> >
>> >
>>
>>
>
>
--
Mark Daniels