Hi all,

I couldn't resist the 2.5 hp motor I mentioned last week. It took a bit
of thinking and several hours work to get it out of the factory, but I
got there in the end. Today I was excited to discover that this motor
was one of the very first steel framed motors, built in 1931, so it's an
interesting historical item too. I might build a phase convertor with
it, or alternatively save it for driving a machine, but so far I haven't
decided.

Here are the photographs I took. The captions explain what is going on:

http://community.webshots.com/album/411757424ARMBqt

A couple of questios too (these are mentioned in the captions). I'm not
sure if the bearings on this motor are intended to be lubricated with
grease or oil. The tubes are currently packed with grease but there
doesn't appear to be any way of forcing it into the bearings, so I can't
see how the system works. See the second from last picture for a view of
the lubrication tubes. Also, I need to free the screws on the motor
mount which adjust the v-belt tension. These are really badly rusted. I
don't mind if I have to make new screws (they are simple threaded rods
with a little tommy bar through the end), but I don't want to damage the
motor mounts. Any ideas?

Hope you enjoy the pictures.

Best wishes,

Chris

Shawn wrote:
"Christopher Tidy" wrote in message
...


I'm not sure if the bearings on this motor are intended to be lubricated

with

grease or oil. The tubes are currently packed with grease but there
doesn't appear to be any way of forcing it into the bearings, so I can't
see how the system works. See the second from last picture for a view of
the lubrication tubes.



Those are grease cups. Fill the cup (cap) with grease and screw it all the
way on.

Oh I see! You fill the cup with grease, then also fill the cap with
grease, and it forces the grease into the bearing as you screw it on?
That makes sense!

Thanks,

Chris

"Christopher Tidy" wrote in message
...

I'm not sure if the bearings on this motor are intended to be lubricated
with
grease or oil. The tubes are currently packed with grease but there
doesn't appear to be any way of forcing it into the bearings, so I can't
see how the system works. See the second from last picture for a view of
the lubrication tubes.


Those are grease cups. Fill the cup (cap) with grease and screw it all the
way on.

Shawn

Not to rain on your parade, but:

If you want to make a 220-240 V phase converter you are going to have to
invest in a transformer to power your motor. Likely, the transformer will
be fairly expensive unless you have "sources" and even then you will end up
with only a 2.5 HP idler. A 2.5 HP idler would make a good phase converter
for only about a 1 HP load. Also before proceeding it'd be a good idea to
have the insulation tested on the motor - another expense. Many years ago,
I bought a very old Wagner Electric 7.5 HP 3-phase motor and made a RPC from
it. It ran only for a couple of years before the insulation went completely
bad. I should have known better when I bought it because it had been stored
outside for a long time and had rotted through the pallet it was sitting on
and fallen down into the mud and snow. Old motors stored outside are not a
good idea.

Bob Swinney


"Christopher Tidy" wrote in message
...
Hi all,

I couldn't resist the 2.5 hp motor I mentioned last week. It took a bit of
thinking and several hours work to get it out of the factory, but I got
there in the end. Today I was excited to discover that this motor was one
of the very first steel framed motors, built in 1931, so it's an
interesting historical item too. I might build a phase convertor with it,
or alternatively save it for driving a machine, but so far I haven't
decided.

Here are the photographs I took. The captions explain what is going on:

http://community.webshots.com/album/411757424ARMBqt

A couple of questios too (these are mentioned in the captions). I'm not
sure if the bearings on this motor are intended to be lubricated with
grease or oil. The tubes are currently packed with grease but there
doesn't appear to be any way of forcing it into the bearings, so I can't
see how the system works. See the second from last picture for a view of
the lubrication tubes. Also, I need to free the screws on the motor mount
which adjust the v-belt tension. These are really badly rusted. I don't
mind if I have to make new screws (they are simple threaded rods with a
little tommy bar through the end), but I don't want to damage the motor
mounts. Any ideas?

Hope you enjoy the pictures.

Best wishes,

Chris

In article ,
Ignoramus6455 wrote:
On Wed, 3 Aug 2005 00:07:46 +0000 (UTC), Christopher Tidy wrote:

Hi all,

Looks like a very interesting motor! It is hostorical...

I am confused. The data plate says that it is a 400V motor. Are you
intending to run it off 220V?

400V and 50 Hz (at least, so I interpret "Periods 50"). You're
in Canada, I think? Or perhaps the UK? (It depends on which way around
the IP address in the "NNTP-Posting-Host: " header reads. Do you have
50Hz power where you are?

If it is 60Hz, then I think that the motor could work at 440V 60
Hz, if designed for 400V 50Hz. In any case, a bit high voltage for your
purposes, though many three-phase machine tools have the option t be
strapped for either 220V or 440V, so you could run them at 440V and not
need as heavy a wire, as the current would be halved. However, you'll
need to boost the incoming power to 440V to run the motor as an idler
int the first place. (That is going to require a heavy transformer.)
And if the motor could be re-strapped for 220V, it would normally have
said so on the data plate.

the lubrication tubes. Also, I need to free the screws on the motor
mount which adjust the v-belt tension. These are really badly rusted. I
don't mind if I have to make new screws (they are simple threaded rods
with a little tommy bar through the end), but I don't want to damage the
motor mounts. Any ideas?

I am not convinced that you need to bother. You are going to have an
idler, there is not going to be any tension or force momentum, other
than instantaneous spinning up of the motor.

Agreed. At most, just screw it down to some 2x4s which stick
out to the sides a bit to keep it from starting to topple. And the RPM
is rather low, so you probably won't have much problem at all.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Okay, can't sleep tonight so I thought I'd come back and read the
messages here :-).

I couldn't resist the 2.5 hp motor I mentioned last week. It took a bit
of thinking and several hours work to get it out of the factory, but I
got there in the end. Today I was excited to discover that this motor
was one of the very first steel framed motors, built in 1931, so it's an
interesting historical item too. I might build a phase convertor with
it, or alternatively save it for driving a machine, but so far I haven't
decided.


Looks like a very interesting motor! It is hostorical...

I am confused. The data plate says that it is a 400V motor. Are you
intending to run it off 220V?

Notice the data plate also says "Connection: Star/Delta". Most three
phase motors are wired in the star configuration for 400 V operation in
the UK, so I assume that the 400 V on the data plate simply refers to
the factory default configuration. There are six terminals under the
cover so it can be rewired in the delta configuration for 230 V.

I am not convinced that you need to bother. You are going to have an
idler, there is not going to be any tension or force momentum, other
than instantaneous spinning up of the motor.

You can set it on a wooden platform (maybe on wheels, make a cradle of
sorts (like a rectangular berm) with 2x4s, and maybe put little
diagonals above mounts to make REALLY sure that the motor does not
jump out one day.

My idler stands like this, and does not jump out of anything. It is on
a small steel tray though, but the tray is simply held by a few junk
wood pieces screwed to the platform neat the sides. The converter
shakes mildly when starting up.

I was thinking of repairing the motor mount for two reasons. Firstly I
was considering building the kind of convertor where a single phase
motor drives the three phase motor permanently, like Dan Caster was
talking about. Secondly I thought I might use this motor for something
else, in which case the mount would probably be handy. But you're quite
right; for the simplest convertor I wouldn't need it.

See

http://igor.chudov.com/projects/Phase-Converter/

http://igor.chudov.com/projects/Phas...e/dscf0011.jpg

the forces involved are very mild.

Your motor is even heavier and spins even slower.

I love seeing pictures, it is like watching a movie.

I love pictures too. Glad you enjoyed them. I'll post more as the
project progresses, though I probably won't begin immediately as I'm
currently working on a farm engine restoration. Might post some pictures
of that soon though...

Best wishes,

Chris

Robert Swinney wrote:
Not to rain on your parade, but:

If you want to make a 220-240 V phase converter you are going to have to
invest in a transformer to power your motor. Likely, the transformer will
be fairly expensive unless you have "sources" and even then you will end up
with only a 2.5 HP idler. A 2.5 HP idler would make a good phase converter
for only about a 1 HP load. Also before proceeding it'd be a good idea to
have the insulation tested on the motor - another expense. Many years ago,
I bought a very old Wagner Electric 7.5 HP 3-phase motor and made a RPC from
it. It ran only for a couple of years before the insulation went completely
bad. I should have known better when I bought it because it had been stored
outside for a long time and had rotted through the pallet it was sitting on
and fallen down into the mud and snow. Old motors stored outside are not a
good idea.

It is rewirable for 230 V (see the "Connection: Star/Delta" on the data
plate). There are also six terminals under the cover. I checked before I
hauled it home!

I might still try to get a transformer. I have a few "sources" who I've
talked to, and they said they'd look out for me. If one turns up cheap
I'll probably buy it, but it's far from essential as most small three
phase motors used here are rewirable for 230 V.

Fortunately this motor hasn't been stored outside, and the roof of the
building doesn't leak yet, so it's only been subjected to damp air at
the worst. There's very little corrosion inside the motor and the
windings look clean and undamaged. I haven't measured the insulation
resistance with a multimeter yet, but I thought I'd take a chance on it.
Even if I'm out of luck we have an excellent motor repair shop nearby
which is about 1/3 the price of other places (I don't know how he does
it). I'll nevertheless leave the motor indoors for a few days before I
power it up, just to make sure the windings are dry.

As for the size of the motor, the largest machine I'd be likely to want
to run from a convertor is a small industrial milling machine, maybe one
of the smallest Bridgeports if I can afford it one day! What size motors
do these use? I haven't definitely decided to use this motor for a
convertor yet. Probably I will recondition it and then decide...

Best wishes,

Chris

And if he has "sources", he could get a $40 like new 10 HP idler, like
I did.

The companies I've asked want about £75 for a 10 hp motor (about $135 I
think). Britain is too expensive :-(. If I wait I can probably get a
bigger motor for nothing, although I'm not sure how big I could go. We
only have a 230 V 45 A supply in the workshop, although this supplies
the workshop alone. I also find free stuff more satisfying, even if I
have to strip it down and recondition it.

By the way, how big is your 10 hp motor and how fast does it spin, Igor?
You can see roughly how large my motor is from the last photo. It shows
me behind it and I'm an average sized guy.

Best wishes,

Chris

The companies I've asked want about £75 for a 10 hp motor (about $135 I
think).


It is unfortunate, but not an incredible amount. With your 45 A, looks
like 10 HP would be a tad too much for your shop.

I reckon I can probably cope with a 5 hp load, but not 10 hp. Of course
I could use a bigger motor for the convertor, but not run it at full
power, but I'm not sure there's much point.

Britain is too expensive :-(. If I wait I can probably get a bigger
motor for nothing, although I'm not sure how big I could go. We only
have a 230 V 45 A supply in the workshop, although this supplies the


My 10 HP is rated for 30 A current. Starting current could be
higher. I have it on a 60A breaker, although, I think, I could get
away with a smaller breaker if I ran the RPC alone. As it is, I have
my compressor on the same circuit.


workshop alone. I also find free stuff more satisfying, even if I
have to strip it down and recondition it.


No doubt. You have a great developing story!


By the way, how big is your 10 hp motor and how fast does it spin,


I just went and measured it. It is roughly 18 by 11 inches, or
0.45x0.28m. It spins at 1940 RPM. It weight approximately 150-180 lbs,
that's just a guesstimate. I could just take it out of the truck when
I came home.

I just measured mine. It's 14" diameter and 16" long without the shaft.
With the shaft it's nearly 20" long. Sometime I will try to weigh it out
of curiosity.

1940 rpm is a weird speed. Are you sure your motor spins at 1940 rpm?
The synchronous speed for a four pole motor on 60 Hz is 1800 rpm, so
1740 rpm would be more likely.

Best wishes,

Chris

An idler uses very little power by itself, except at startup. Perhaps
you can make a staged phase converter, with one starting idler and a
second idler that you would switch on once the first idler is up to
speed.

I had wondered about this, but for different reasons. I wondered if you
could have three-motor convertor and somehow connect them to give a
perfectly balanced output, but I haven't been able to figure out a
scheme to do this so far.

I just went and measured it. It is roughly 18 by 11 inches, or
0.45x0.28m. It spins at 1940 RPM. It weight approximately 150-180

lbs,

TYPO ALERT: it is 1740 RPM.


that's just a guesstimate. I could just take it out of the truck when
I came home.

I just measured mine. It's 14" diameter and 16" long without the shaft.
With the shaft it's nearly 20" long. Sometime I will try to weigh it out
of curiosity.


Hm, not very different from my motor... (only mine is 4 times the
HP). I would be interested to know the weight.

That extra 3" on the diameter probably adds quite a bit to the weight.
I'll weigh it tomorrow if I can find our old bathroom scales.

Chris

Shawn wrote:
"Christopher Tidy" wrote in message
...


I'm not sure if the bearings on this motor are intended to be lubricated

with

grease or oil. The tubes are currently packed with grease but there
doesn't appear to be any way of forcing it into the bearings, so I can't
see how the system works. See the second from last picture for a view of
the lubrication tubes.



Those are grease cups. Fill the cup (cap) with grease and screw it all the
way on.

Shawn



I thought you filled the cup and then gave the cap a turn every once in
a while..

i haven't been following ignoramus' thread closely but i wanted to say,
years ago, um, YEARS ago there was a short article in fine woodworking
magazine about building a rotary phase converter. i did it. it works fine.
i believe the article said it should be in an insulated enclosed box with a
heat source (light bulb) for cold weather starting. (i never built the
box). the article ignoramus quoted mentions a "pull rope" version, that's
the one i made. i guess it's a bit more of a pain in the butt to start with
a pull rope instead of with capacitors, but it's simple and it's for a wood
cutting bandsaw that i don't use very often. there's a guy with a machine
shop down the road from me here, i was surprised when i saw he has a
electric motor constantly spinning outside the side door of his shop.

JohnM wrote:
Shawn wrote:

"Christopher Tidy" wrote in message
...


I'm not sure if the bearings on this motor are intended to be lubricated


with

grease or oil. The tubes are currently packed with grease but there
doesn't appear to be any way of forcing it into the bearings, so I can't
see how the system works. See the second from last picture for a view of
the lubrication tubes.




Those are grease cups. Fill the cup (cap) with grease and screw it
all the
way on.

Shawn



I thought you filled the cup and then gave the cap a turn every once in
a while..

I searched the web for "grease cup" and found a site saying just that.
It makes good sense, so that's what I'll do.

Chris

Chris sez:

" It is rewirable for 230 V (see the "Connection: Star/Delta" on the data
plate). There are also six terminals under the cover. I checked before I
hauled it home!"
-- and -- "There's very little corrosion inside the motor and the
windings look clean and undamaged. I haven't measured the insulation
resistance with a multimeter yet, but I thought I'd take a chance on it."

Be careful here. I didn't get the impression it was strappable for 230 -
460 from the pix of the nameplate. "Star/Delta" refers to the way the
windings can be configured for approx. a 1.7 x change in operating voltage.
Generally, a dual voltage motor (one strappable for 230 - 460) has 9 leads
available under the cover. Also, better take it to a motor shop for
insulation verification with a "meggohmmeter". Not something you can do
with an ordinary multimeter.

Bob Swinney

I just measured mine. It's 14" diameter and 16" long without the shaft.
With the shaft it's nearly 20" long. Sometime I will try to weigh it out
of curiosity.

Hm, not very different from my motor... (only mine is 4 times the
HP). I would be interested to know the weight.

I just weighed the motor. It's a little heavier than I thought: 94 kg
(207 lb). I'd be interested to know what yours weighs if you ever weigh
it, too.

Best wishes,

Chris

Shawn wrote:
"JohnM" wrote in message
m...

Shawn wrote:

"Christopher Tidy" wrote in message
...



I'm not sure if the bearings on this motor are intended to be lubricated

with


grease or oil. The tubes are currently packed with grease but there
doesn't appear to be any way of forcing it into the bearings, so I can't
see how the system works. See the second from last picture for a view of
the lubrication tubes.



Those are grease cups. Fill the cup (cap) with grease and screw it all

the

way on.

Shawn



I thought you filled the cup and then gave the cap a turn every once in
a while..


You're right, I did not give a complete explanation. Look for a number
stamped on the motor frame near the grease tube or on the grease cup. That
number will be how many ounces of grease to apply to the bearing when
lubricating. If this is like the grease cupped motors I am accustomed to,
the periodicity will be about every other month. Since this motor will
likely see service as a rotary converter with no physical loading on the
motor shaft, you may not need to grease as often.

Interesting. Is that every other month when the motor is running
continuously, or just when it is used frequently? In its original
application I imagine this motor would have run pretty much continuously
during the winter months.

Best wishes,

Chris

Robert Swinney wrote:
Chris sez:

" It is rewirable for 230 V (see the "Connection: Star/Delta" on the data
plate). There are also six terminals under the cover. I checked before I
hauled it home!"
-- and -- "There's very little corrosion inside the motor and the
windings look clean and undamaged. I haven't measured the insulation
resistance with a multimeter yet, but I thought I'd take a chance on it."

Be careful here. I didn't get the impression it was strappable for 230 -
460 from the pix of the nameplate. "Star/Delta" refers to the way the
windings can be configured for approx. a 1.7 x change in operating voltage.

Isn't this the same thing? 230 V * sqrt(3) = 400 V.

Generally, a dual voltage motor (one strappable for 230 - 460) has 9 leads
available under the cover.

What are the nine leads for? Most of the three phase motors I've seen in
the UK either have three leads (permanent star connection) or six leads
(both ends of each winding brought out, so it can be connected star or
delta). I also saw a six lead motor which was dual wound (i.e., two
completely separate windings, a four pole and a six pole, both with
permanent star connections).

Also, better take it to a motor shop for
insulation verification with a "meggohmmeter". Not something you can do
with an ordinary multimeter.

Do you mean one of those hand cranked insulation testing generators? I'm
not too keen to take the motor to a rewind shop to have it tested
because of the weight. In the past I've just made sure a motor is dry,
measured the insulation resistance with a multimeter to find obvious
faults, wired it up through a low value fuse and kept an eye on it. I've
not had problems so far.

Best wishes,

Chris

"JohnM" wrote in message
m...
Shawn wrote:
"Christopher Tidy" wrote in message
...


I'm not sure if the bearings on this motor are intended to be lubricated

with

grease or oil. The tubes are currently packed with grease but there
doesn't appear to be any way of forcing it into the bearings, so I can't
see how the system works. See the second from last picture for a view of
the lubrication tubes.



Those are grease cups. Fill the cup (cap) with grease and screw it all
the
way on.

Shawn



I thought you filled the cup and then gave the cap a turn every once in
a while..

You're right, I did not give a complete explanation. Look for a number
stamped on the motor frame near the grease tube or on the grease cup. That
number will be how many ounces of grease to apply to the bearing when
lubricating. If this is like the grease cupped motors I am accustomed to,
the periodicity will be about every other month. Since this motor will
likely see service as a rotary converter with no physical loading on the
motor shaft, you may not need to grease as often.

Shawn

Ignoramus20106 wrote:
On Wed, 3 Aug 2005 12:19:35 +0000 (UTC), Christopher Tidy wrote:

I just measured mine. It's 14" diameter and 16" long without the shaft.
With the shaft it's nearly 20" long. Sometime I will try to weigh it out
of curiosity.

Hm, not very different from my motor... (only mine is 4 times the
HP). I would be interested to know the weight.

I just weighed the motor. It's a little heavier than I thought: 94 kg
(207 lb). I'd be interested to know what yours weighs if you ever weigh
it, too.

Mine is inside the phase converter, screwed down to the platform. Kind
of hard to take out to weigh. I would say, as a wild guess, 180 lbs or
80 kg. I could lift it out of the truck and place on a furniture
moving platform, but with difficulty.

No problem, just curious. Is the phase convertor finished now? It looks
like your motor is probably a little lighter, which is interesting.
Motor design and construction must have changed a great deal in 60 or 70
years, although a slow-running motor will always be larger than a
fast-running motor of the same power rating.

Good luck with the project! I'll let you know how mine goes.

Best wishes,

Chris

Igor,

By the way, I went to your website twice to look at the photos this
morning and it isn't working. It says "connection refused". Just thought
you might like to know.

Chris

Ignoramus20106 wrote:
On Wed, 3 Aug 2005 13:47:47 +0000 (UTC), Christopher Tidy wrote:

Igor,

By the way, I went to your website twice to look at the photos this
morning and it isn't working. It says "connection refused". Just thought
you might like to know.


I think that I corrected it... something went wrong last night.

Yes, works now.

Chris

"Christopher Tidy" wrote in message
...
Robert Swinney wrote:
Chris sez:

" It is rewirable for 230 V (see the "Connection: Star/Delta" on the data
plate). There are also six terminals under the cover. I checked before I
hauled it home!"
-- and -- "There's very little corrosion inside the motor and the
windings look clean and undamaged. I haven't measured the insulation
resistance with a multimeter yet, but I thought I'd take a chance on
it."

Be careful here. I didn't get the impression it was strappable for 230 -
460 from the pix of the nameplate. "Star/Delta" refers to the way the
windings can be configured for approx. a 1.7 x change in operating
voltage.

Isn't this the same thing? 230 V * sqrt(3) = 400 V.

Generally, a dual voltage motor (one strappable for 230 - 460) has 9
leads available under the cover.

What are the nine leads for? Most of the three phase motors I've seen in
the UK either have three leads (permanent star connection) or six leads
(both ends of each winding brought out, so it can be connected star or
delta). I also saw a six lead motor which was dual wound (i.e., two
completely separate windings, a four pole and a six pole, both with
permanent star connections).

Also, better take it to a motor shop for insulation verification with a
"meggohmmeter". Not something you can do with an ordinary multimeter.

Do you mean one of those hand cranked insulation testing generators? I'm
not too keen to take the motor to a rewind shop to have it tested because
of the weight. In the past I've just made sure a motor is dry, measured
the insulation resistance with a multimeter to find obvious faults, wired
it up through a low value fuse and kept an eye on it. I've not had
problems so far.

Best wishes,

Chris

"Christopher Tidy" wrote in message
...
Robert Swinney wrote:
Chris sez:

" It is rewirable for 230 V (see the "Connection: Star/Delta" on the data
plate). There are also six terminals under the cover. I checked before I
hauled it home!"
-- and -- "There's very little corrosion inside the motor and the
windings look clean and undamaged. I haven't measured the insulation
resistance with a multimeter yet, but I thought I'd take a chance on
it."

Be careful here. I didn't get the impression it was strappable for 230 -
460 from the pix of the nameplate. "Star/Delta" refers to the way the
windings can be configured for approx. a 1.7 x change in operating
voltage.

Isn't this the same thing? 230 V * sqrt(3) = 400 V.

Sorry Chris, You are correct! With 6 leads brought out, the motor must be
externally configurable for "Star" or "Delta". This would be in agreement
with what your name plate says, "star-delta". And your math is correct,
also; Converting from one configuration to the other does yield a sq.root of
3 change in voltage and vs. Assume the 6 leads brought out from each
internal phase group are thus; (1 and 5), (2 and 6), (3 and 4); therefore
the "star" configuration would be; 4, 5, and 6 strapped together and
incoming lines connected to 1, 2, and 3. This would be the high voltage
connection.

For low voltage operation the "delta" configuration would be: (1,6 and line
1 together), (4,5 and line 2 together) and (2,3 and line 3 together).

Generally, a dual voltage motor (one strappable for 230 - 460) has 9
leads available under the cover.

What are the nine leads for? Most of the three phase motors I've seen in
the UK either have three leads (permanent star connection) or six leads
(both ends of each winding brought out, so it can be connected star or
delta). I also saw a six lead motor which was dual wound (i.e., two
completely separate windings, a four pole and a six pole, both with
permanent star connections).

The 9 lead arrangement is more common in the U.S. It provides a method of
connecting internal coil groups either in series or parallel to achieve dual
voltage operation.

Also, better take it to a motor shop for insulation verification with a
"meggohmmeter". Not something you can do with an ordinary multimeter.

Do you mean one of those hand cranked insulation testing generators? I'm
not too keen to take the motor to a rewind shop to have it tested because
of the weight. In the past I've just made sure a motor is dry, measured
the insulation resistance with a multimeter to find obvious faults, wired
it up through a low value fuse and kept an eye on it. I've not had
problems so far.

Precisely. A "megger" test would reveal insulation break down that would
not be detectable with an ordinary VOM. Perhaps you could borrow, or rent,
a megger and take it to your location. It is more than a little
disconcerting to hear a gun-shot like "crack" coming from a RPC you already
have a lot of time and money invested in.

Bob Swinney

On Wed, 3 Aug 2005 14:03:26 +0000 (UTC), Christopher Tidy
wrote:

Ignoramus20106 wrote:
On Wed, 3 Aug 2005 13:47:47 +0000 (UTC), Christopher Tidy wrote:

Igor,

By the way, I went to your website twice to look at the photos this
morning and it isn't working. It says "connection refused". Just thought
you might like to know.


I think that I corrected it... something went wrong last night.

Yes, works now.

Chris

Greetings Chris,
Just to give you some hope about your motor here's a little story. In
1980 I worked in a lumbermill that had lots of antique equipment in
daily use. And used hard. There were several shelves with big motors
on them that were used when another motor needed repair or
replacement. These were OLD motors. They were much larger in diameter
than long. The frames were cast iron and were cast in those nice
curves you see on old machines. Each motor had an eye on top and it
would take two guys to lift one. 2 inch diameter shafts. And these
were only 3 HP motors! Usually the reason for replacement or repair
was because the millwrights or the oilers neglected the motor because
of location. The babbit bearings would melt. And so the motor would be
switched with one that had good bearings and I would get to pour new
bearings for the bad motor and put it back on the shelf. The whole
mill was basically open to the elements. It had a tin roof and sides
but no doors, just openings. Some were pretty big. So the wind would
whip through the mill bringing rain or snow with it. But none of the
old motors failed because of insulation. Since they were open frame
motors subjected to all the wood fragments flying around the motors
would sometimes have their windings damaged from stuff jammed in them.
Some of these motors had cloth insulation. Some were equipped with
brushes. I think these were repulsion start, induction run motors. So
your motor, being protected indoors, probably has good insulation.
ERS

In article ,
Robert Swinney wrote:

"Christopher Tidy" wrote in message
...

[ ... ]

What are the nine leads for? Most of the three phase motors I've seen in
the UK either have three leads (permanent star connection) or six leads
(both ends of each winding brought out, so it can be connected star or
delta). I also saw a six lead motor which was dual wound (i.e., two
completely separate windings, a four pole and a six pole, both with
permanent star connections).

The 9 lead arrangement is more common in the U.S. It provides a method of
connecting internal coil groups either in series or parallel to achieve dual
voltage operation.

In particular, picture this:

1) Three windings for the lower voltage of two differing by a
factor of two. These are permanently connected in Wye.

three leads to the outside world.

2) Three more windings of the same voltage, but totally separate
so both ends of each are brought out.

six more leads to the outside world.

Total of nine leads to the outside world, before configuring as
either a 240V or a 480V motor.

3) Now, if you want it to run at the lower voltage, you connect
the three windings from (2) above into another Wye, insulate the
center and connect the three remaining leads to the three from
the winding in (1) above. Bring a wire out from the junction of
the winding from (1) and the winding from (2) to connect to the
power. (Of course, it makes a difference which windings and
where they are connected, so each wire should have either a
crimped on ring with the number, or the number printed along the
wire every inch or two.) The windings from (2) are in parallel
with those from (1), so they run at the same voltage, and each
carries half the current.

4) If you want it to run at the higher voltage, however, you
connect one end of each of the three coils in (2) above to one
of the three wires from (1) above, so the coil from (2) is in
series with the coil from (1). Proceed to do the same with each
of the two remaining coils. Insulate each of these junctions.
Bring the free ends of each of the windings from (2) out to
connect to the power. In this case, the windings from (2) are
in series with the windings from (1), so the voltage is double
that with the (3) setup, and the current is half that with the
(3) setup. Again, which winding is where is important, so
again you refer to the numbers either crimped around or printed
on the wires.

In either case, there should be printed on the motor's nameplate
which numbers of wires should be connected together and whether they
should be connected to the outside or just insulated.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"DoN. Nichols" wrote in message
...
In article ,
Robert Swinney wrote:

"Christopher Tidy" wrote in message
...

[ ... ]

What are the nine leads for? Most of the three phase motors I've seen in
the UK either have three leads (permanent star connection) or six leads
(both ends of each winding brought out, so it can be connected star or
delta). I also saw a six lead motor which was dual wound (i.e., two
completely separate windings, a four pole and a six pole, both with
permanent star connections).

The 9 lead arrangement is more common in the U.S. It provides a method of
connecting internal coil groups either in series or parallel to achieve
dual
voltage operation.

In particular, picture this:

1) Three windings for the lower voltage of two differing by a
factor of two. These are permanently connected in Wye.

three leads to the outside world.

2) Three more windings of the same voltage, but totally separate
so both ends of each are brought out.

six more leads to the outside world.

Total of nine leads to the outside world, before configuring as
either a 240V or a 480V motor.

3) Now, if you want it to run at the lower voltage, you connect
the three windings from (2) above into another Wye, insulate the
center and connect the three remaining leads to the three from
the winding in (1) above. Bring a wire out from the junction of
the winding from (1) and the winding from (2) to connect to the
power. (Of course, it makes a difference which windings and
where they are connected, so each wire should have either a
crimped on ring with the number, or the number printed along the
wire every inch or two.) The windings from (2) are in parallel
with those from (1), so they run at the same voltage, and each
carries half the current.

4) If you want it to run at the higher voltage, however, you
connect one end of each of the three coils in (2) above to one
of the three wires from (1) above, so the coil from (2) is in
series with the coil from (1). Proceed to do the same with each
of the two remaining coils. Insulate each of these junctions.
Bring the free ends of each of the windings from (2) out to
connect to the power. In this case, the windings from (2) are
in series with the windings from (1), so the voltage is double
that with the (3) setup, and the current is half that with the
(3) setup. Again, which winding is where is important, so
again you refer to the numbers either crimped around or printed
on the wires.

In either case, there should be printed on the motor's nameplate
which numbers of wires should be connected together and whether they
should be connected to the outside or just insulated.

His name plate only said star/delta thus he had no standard 9 wires to work
with. He achieves hi V, loV by connecting the motor in star or delta
apparently.

Bob Swinney

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
Robert Swinney wrote:

"DoN. Nichols" wrote in message
...
In article ,
Robert Swinney wrote:

"Christopher Tidy" wrote in message
...

[ ... ]

What are the nine leads for? Most of the three phase motors I've seen in

[ ... ]

In either case, there should be printed on the motor's nameplate
which numbers of wires should be connected together and whether they
should be connected to the outside or just insulated.

His name plate only said star/delta thus he had no standard 9 wires to work
with. He achieves hi V, loV by connecting the motor in star or delta
apparently.

I understood that -- but he *asked* about the 9-wire setup (see
quoted line above), so I decided to explain it in more detail than you
did. He is unlikely to run into the nine-wire motors in the UK, I
think.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

DoN. Nichols wrote:

What are the nine leads for? Most of the three phase motors I've seen in
the UK either have three leads (permanent star connection) or six leads
(both ends of each winding brought out, so it can be connected star or
delta). I also saw a six lead motor which was dual wound (i.e., two
completely separate windings, a four pole and a six pole, both with
permanent star connections).

The 9 lead arrangement is more common in the U.S. It provides a method of
connecting internal coil groups either in series or parallel to achieve dual
voltage operation.


In particular, picture this:

1) Three windings for the lower voltage of two differing by a
factor of two. These are permanently connected in Wye.

three leads to the outside world.

2) Three more windings of the same voltage, but totally separate
so both ends of each are brought out.

six more leads to the outside world.

Total of nine leads to the outside world, before configuring as
either a 240V or a 480V motor.

3) Now, if you want it to run at the lower voltage, you connect
the three windings from (2) above into another Wye, insulate the
center and connect the three remaining leads to the three from
the winding in (1) above. Bring a wire out from the junction of
the winding from (1) and the winding from (2) to connect to the
power. (Of course, it makes a difference which windings and
where they are connected, so each wire should have either a
crimped on ring with the number, or the number printed along the
wire every inch or two.) The windings from (2) are in parallel
with those from (1), so they run at the same voltage, and each
carries half the current.

4) If you want it to run at the higher voltage, however, you
connect one end of each of the three coils in (2) above to one
of the three wires from (1) above, so the coil from (2) is in
series with the coil from (1). Proceed to do the same with each
of the two remaining coils. Insulate each of these junctions.
Bring the free ends of each of the windings from (2) out to
connect to the power. In this case, the windings from (2) are
in series with the windings from (1), so the voltage is double
that with the (3) setup, and the current is half that with the
(3) setup. Again, which winding is where is important, so
again you refer to the numbers either crimped around or printed
on the wires.

In either case, there should be printed on the motor's nameplate
which numbers of wires should be connected together and whether they
should be connected to the outside or just insulated.

Enjoy,
DoN.

Thanks for the explantion, Don. I've never seen a motor like this in
England. We often get 115/230 V single phase motors which have two
identical windings which can be connected in series or parallel, but not
three phase motors. You just connect them in the star configuration for
400 V or the delta configuration for 230 V. The 230 V can be obtained
from an industrial three phase supply as it is the voltage between any
one phase conductor and neutral. Do you have 115 V, 230 V AND 460 V
supplies in the USA?

Thanks for explaining!

Chris

Eric R Snow wrote:

Greetings Chris,
Just to give you some hope about your motor here's a little story. In
1980 I worked in a lumbermill that had lots of antique equipment in
daily use. And used hard. There were several shelves with big motors
on them that were used when another motor needed repair or
replacement. These were OLD motors. They were much larger in diameter
than long. The frames were cast iron and were cast in those nice
curves you see on old machines. Each motor had an eye on top and it
would take two guys to lift one. 2 inch diameter shafts. And these
were only 3 HP motors! Usually the reason for replacement or repair
was because the millwrights or the oilers neglected the motor because
of location. The babbit bearings would melt. And so the motor would be
switched with one that had good bearings and I would get to pour new
bearings for the bad motor and put it back on the shelf. The whole
mill was basically open to the elements. It had a tin roof and sides
but no doors, just openings. Some were pretty big. So the wind would
whip through the mill bringing rain or snow with it. But none of the
old motors failed because of insulation. Since they were open frame
motors subjected to all the wood fragments flying around the motors
would sometimes have their windings damaged from stuff jammed in them.
Some of these motors had cloth insulation. Some were equipped with
brushes. I think these were repulsion start, induction run motors. So
your motor, being protected indoors, probably has good insulation.
ERS

Thanks for the fascinating story. Whereabouts was your lumber mill? It
reminds me of some web pages about lumber mills I saw a while back. You
might find them interesting:

http://www.sentex.net/~mwandel/sawmill/asam.html
http://www.sentex.net/~mwandel/sawmill/sawmill.html

My grandfather and great uncle used to run a granary in England, but it
shut before I was born. It's a pity as it dated back over a century and
I would have loved to have seen it in operation.

I think there's a good chance my motor's insulation is okay, but if not
I'll probably get it fixed sometime anyway.

Best wishes,

Chris

Robert Swinney wrote:
"Christopher Tidy" wrote in message
...

Robert Swinney wrote:

Chris sez:

" It is rewirable for 230 V (see the "Connection: Star/Delta" on the data
plate). There are also six terminals under the cover. I checked before I
hauled it home!"
-- and -- "There's very little corrosion inside the motor and the
windings look clean and undamaged. I haven't measured the insulation
resistance with a multimeter yet, but I thought I'd take a chance on
it."

Be careful here. I didn't get the impression it was strappable for 230 -
460 from the pix of the nameplate. "Star/Delta" refers to the way the
windings can be configured for approx. a 1.7 x change in operating
voltage.

Isn't this the same thing? 230 V * sqrt(3) = 400 V.


Sorry Chris, You are correct! With 6 leads brought out, the motor must be
externally configurable for "Star" or "Delta". This would be in agreement
with what your name plate says, "star-delta". And your math is correct,
also; Converting from one configuration to the other does yield a sq.root of
3 change in voltage and vs. Assume the 6 leads brought out from each
internal phase group are thus; (1 and 5), (2 and 6), (3 and 4); therefore
the "star" configuration would be; 4, 5, and 6 strapped together and
incoming lines connected to 1, 2, and 3. This would be the high voltage
connection.

For low voltage operation the "delta" configuration would be: (1,6 and line
1 together), (4,5 and line 2 together) and (2,3 and line 3 together).

Generally, a dual voltage motor (one strappable for 230 - 460) has 9
leads available under the cover.

What are the nine leads for? Most of the three phase motors I've seen in
the UK either have three leads (permanent star connection) or six leads
(both ends of each winding brought out, so it can be connected star or
delta). I also saw a six lead motor which was dual wound (i.e., two
completely separate windings, a four pole and a six pole, both with
permanent star connections).


The 9 lead arrangement is more common in the U.S. It provides a method of
connecting internal coil groups either in series or parallel to achieve dual
voltage operation.

Also, better take it to a motor shop for insulation verification with a
"meggohmmeter". Not something you can do with an ordinary multimeter.

Do you mean one of those hand cranked insulation testing generators? I'm
not too keen to take the motor to a rewind shop to have it tested because
of the weight. In the past I've just made sure a motor is dry, measured
the insulation resistance with a multimeter to find obvious faults, wired
it up through a low value fuse and kept an eye on it. I've not had
problems so far.


Precisely. A "megger" test would reveal insulation break down that would
not be detectable with an ordinary VOM. Perhaps you could borrow, or rent,
a megger and take it to your location. It is more than a little
disconcerting to hear a gun-shot like "crack" coming from a RPC you already
have a lot of time and money invested in.

Aargh! I saw one of those cheap on eBay last year, but didn't bid as I
didn't think I had a use for it. I bet they're expensive pieces of kit
normally. What does the hand-cranked megger actually do? I'll keep an
eye out for one. Maybe another will turn up on eBay...

Best wishes,

Chris

Precisely. A "megger" test would reveal insulation break down that would
not be detectable with an ordinary VOM. Perhaps you could borrow, or
rent, a megger and take it to your location. It is more than a little
disconcerting to hear a gun-shot like "crack" coming from a RPC you
already have a lot of time and money invested in.

Aargh! I saw one of those cheap on eBay last year, but didn't bid as I
didn't think I had a use for it. I bet they're expensive pieces of kit
normally. What does the hand-cranked megger actually do? I'll keep an eye
out for one. Maybe another will turn up on eBay...

Basically they are ohmmeters for reading "leakage" resistance such as found
in motors, transformers and other devices with coils of wire.

Bob Swinney

On Thu, 4 Aug 2005 06:19:01 +0000 (UTC), Christopher Tidy
wrote:

Eric R Snow wrote:

Greetings Chris,
Just to give you some hope about your motor here's a little story. In
1980 I worked in a lumbermill that had lots of antique equipment in
daily use. And used hard. There were several shelves with big motors
on them that were used when another motor needed repair or
replacement. These were OLD motors. They were much larger in diameter
than long. The frames were cast iron and were cast in those nice
curves you see on old machines. Each motor had an eye on top and it
would take two guys to lift one. 2 inch diameter shafts. And these
were only 3 HP motors! Usually the reason for replacement or repair
was because the millwrights or the oilers neglected the motor because
of location. The babbit bearings would melt. And so the motor would be
switched with one that had good bearings and I would get to pour new
bearings for the bad motor and put it back on the shelf. The whole
mill was basically open to the elements. It had a tin roof and sides
but no doors, just openings. Some were pretty big. So the wind would
whip through the mill bringing rain or snow with it. But none of the
old motors failed because of insulation. Since they were open frame
motors subjected to all the wood fragments flying around the motors
would sometimes have their windings damaged from stuff jammed in them.
Some of these motors had cloth insulation. Some were equipped with
brushes. I think these were repulsion start, induction run motors. So
your motor, being protected indoors, probably has good insulation.
ERS

Thanks for the fascinating story. Whereabouts was your lumber mill? It
reminds me of some web pages about lumber mills I saw a while back. You
might find them interesting:

http://www.sentex.net/~mwandel/sawmill/asam.html
http://www.sentex.net/~mwandel/sawmill/sawmill.html

My grandfather and great uncle used to run a granary in England, but it
shut before I was born. It's a pity as it dated back over a century and
I would have loved to have seen it in operation.

I think there's a good chance my motor's insulation is okay, but if not
I'll probably get it fixed sometime anyway.

Best wishes,

Chris
It wasn't my lumbermill. It was located in the Sierra mountains above
Sonora CA.
Eric

In article , Eric R Snow says...

whip through the mill bringing rain or snow with it. But none of the
old motors failed because of insulation. Since they were open frame
motors subjected to all the wood fragments flying around the motors
would sometimes have their windings damaged from stuff jammed in them.

LOL. The man who taught me to build phase converters built his
one originally from a motor he was given when a sawmill shut down.
He said it looked like the bearings on it had been toased because
the armature was locked solid.

Turns out the space between the armature and the stator was
packed solid full of sawdust!! He cleaned it out and has been
using that converter for years now.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

Iggy sez:

"Very interesting. I wonder how easy it is to practically disassemble
large motors. I'd like to buy a smallish 3 phase motor one day for
next to nothing and take it apart to show my son how it works."

It is very easy to disassemble most motors. From my experience, (usually)
the end bells are an easy press fit onto the case at both ends. The end
bells are held in place with through bolts. Remove the bolts, usu. 4, and
mark the orientation of both end bells to the case. Start to break the end
bells' fit into the case by tapping with a narrow screw driver or knife
edge. Gently pry around the periphery until the bells seperate from the
case. After the end bells are clear of the case the rotor can be pulled out
from either end.

Bob Swinney

jim rozen wrote:
In article , Eric R Snow says...


whip through the mill bringing rain or snow with it. But none of the
old motors failed because of insulation. Since they were open frame
motors subjected to all the wood fragments flying around the motors
would sometimes have their windings damaged from stuff jammed in them.


LOL. The man who taught me to build phase converters built his
one originally from a motor he was given when a sawmill shut down.
He said it looked like the bearings on it had been toased because
the armature was locked solid.

Turns out the space between the armature and the stator was
packed solid full of sawdust!! He cleaned it out and has been
using that converter for years now.

Cool! Do you recall what size of motor he acquired and what sort of
tools he ran? I'm just trying to figure out how good my 2.5 hp motor
(which it seems is pretty similar to some of the motors used in old
mills) would be for a phase converter. I'd probably be making a more
sophisticated converter with run capacitors, etc.

Chris

"Very interesting. I wonder how easy it is to practically disassemble

large motors. I'd like to buy a smallish 3 phase motor one day for
next to nothing and take it apart to show my son how it works."


It is very easy to disassemble most motors. From my experience, (usually)
the end bells are an easy press fit onto the case at both ends. The end
bells are held in place with through bolts. Remove the bolts, usu. 4, and
mark the orientation of both end bells to the case. Start to break the end
bells' fit into the case by tapping with a narrow screw driver or knife
edge. Gently pry around the periphery until the bells seperate from the
case. After the end bells are clear of the case the rotor can be pulled out
from either end.

Most motors are easy to disassemble, but you'll find a few which are
horrible! Look for a motor which has end bells which are larger than the
stator, or at least end bells which have protrusions you can tap or
lever against. If the end bells are tight you can try heating the stator
gently with a heat gun, but this might damage the paintwork. If the
bearing seems to be tight in the end bell, you can warm the hub of the
end bell.

Most modern TEFC motors are straightforward to disassemble. You should
be able to disassemble and reassemble a motor without doing any damage,
so afterwards you can sell it on eBay or use it. On the other hand there
isn't a great deal to see inside a three phase motor.

A cool demonstration is to apply power to the stator without the rotor
present and put a coke can inside. Make an axle and handle for the coke
can so that it can't escape! You'll probably need to reduce the voltage
applied to the stator, partly to make it safer and partly to avoid
overheating the motor.

Chris

In article ,
Christopher Tidy wrote:
DoN. Nichols wrote:

What are the nine leads for? Most of the three phase motors I've seen in

[ ... ]

In particular, picture this:

[ ... lots snipped ... ]

In either case, there should be printed on the motor's nameplate
which numbers of wires should be connected together and whether they
should be connected to the outside or just insulated.

Enjoy,
DoN.

Thanks for the explantion, Don. I've never seen a motor like this in
England. We often get 115/230 V single phase motors which have two
identical windings which can be connected in series or parallel, but not
three phase motors. You just connect them in the star configuration for
400 V or the delta configuration for 230 V. The 230 V can be obtained
from an industrial three phase supply as it is the voltage between any
one phase conductor and neutral. Do you have 115 V, 230 V AND 460 V
supplies in the USA?

Domestic power is a mix of 115 and 230V (or 120/240 depending on
who is saying it) I'll use the 120/240V below.

Picture a transformer winding (at the street), with 240V AC
across the winding, but with a center tap which is grounded. All three
wires are run to the house (with the grounded center tap wire often
uninsulated). It is routed through the KWH (KiloWatt Hours) meter, and
into the breaker panel. There are two buses run vertically in the
panel, with fingers reaching out to left and right (and passing by the
other bus). This means that any single circuit breaker gets 120VAC, but
any two side by side bring out 240V between them. Breakers for 240V are
actually two breakers riveted side by side, with a mechanical linkage
between the arms so if one trips, both go. (Or, sometimes, both breakers
are built within a single housing, with a single toggle to work both at
the same time.)

Wires run from the breaker panel contain one or more hots, an
associated neutral, and a safety ground. (Not all are present in all
cases.)

Most wall outlets in the USA are 120VAC, so one side is
neutral,and the other 120VAC.

Certain appliances need more power, so they run from a double
breaker at 240V. Examples of this include electric kitchen stoves, and
electric clothes dryers. (Electric water heaters are also 240V devices,
but they are normally not fitted with an outlet and plug -- they are
hard-wired to the breaker panel from the water heater.)

Note that while this provides 240VAC for these higher power
loads, still the maximum voltage above ground is no more than 120VAC.
The lines are 180 degrees out of phase (not a useful phase difference
for starting three-phase motors, but useful for getting double the
voltage to a load while keeping the voltage above ground within reason).
This comment about "180 degrees out of phase" will usually fire up some
who believe that it is a mistatement of facts, but it depends on how you
look at it. :-)

It is *very* difficult for the typical city home to get three
phase power, and it is charged at industrial rates. This means that your
whole month is charged as though your highest current drain at any time
during that month was being drawn for the whole month. One person who I
know discovered this to his disadvantage when he fired up a large
heat-treat oven which he acquired surplus. He had three phase, because
he was living in what used to be a commercial shop, and it was still a
machine shop -- he was just living in there. :-)

But -- if you *do* have three phase power, the breaker box has
three buses, arranged in a manner similar to the two bus one for 220V,
except that groups of three breakers make up a full three-phase
connection, groups of two make up a 240V connection, and single ones
*may* be 120V, depending on the service. One common one for use where
120V and three phase are both needed is to ground the center tap of one
of the three phases, which allows two out of three breakers to provide
120VAC. The third one (the "wild leg") produces a much higher voltage,
and should *not* be used for 120V loads. I don't know whether the breaker
panels have a provision for preventing a single breaker from entering
the "wild-leg" slots, or whether they depend on the electrician knowing
what he is doing. :-)

Double breakers can be used in any adjacent pair of slots for
240VAC loads, and triple breakers in any adjacent three slots for three
phase output.

Note that all of the above are delta connections. There are
three phase Wye connections where any single phase to neutral/ground is
120VAC, and between any two phases is 208VAC IIRC. This is why some
motors are rated for 208V-204V.

And also note one other difference from the UK -- the power
frequency is 60 Hz, not 50 Hz. (You can get away with a little less
iron in motors and transformers for 60 Hz compared to 50 Hz.

Thanks for explaining!

You're welcome,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Thanks for the explantion, Don. I've never seen a motor like this in
England. We often get 115/230 V single phase motors which have two
identical windings which can be connected in series or parallel, but not
three phase motors. You just connect them in the star configuration for
400 V or the delta configuration for 230 V. The 230 V can be obtained

from an industrial three phase supply as it is the voltage between any

one phase conductor and neutral. Do you have 115 V, 230 V AND 460 V
supplies in the USA?


Domestic power is a mix of 115 and 230V (or 120/240 depending on
who is saying it) I'll use the 120/240V below.

Picture a transformer winding (at the street), with 240V AC
across the winding, but with a center tap which is grounded. All three
wires are run to the house (with the grounded center tap wire often
uninsulated). It is routed through the KWH (KiloWatt Hours) meter, and
into the breaker panel. There are two buses run vertically in the
panel, with fingers reaching out to left and right (and passing by the
other bus). This means that any single circuit breaker gets 120VAC, but
any two side by side bring out 240V between them. Breakers for 240V are
actually two breakers riveted side by side, with a mechanical linkage
between the arms so if one trips, both go. (Or, sometimes, both breakers
are built within a single housing, with a single toggle to work both at
the same time.)

Wires run from the breaker panel contain one or more hots, an
associated neutral, and a safety ground. (Not all are present in all
cases.)

Most wall outlets in the USA are 120VAC, so one side is
neutral,and the other 120VAC.

Certain appliances need more power, so they run from a double
breaker at 240V. Examples of this include electric kitchen stoves, and
electric clothes dryers. (Electric water heaters are also 240V devices,
but they are normally not fitted with an outlet and plug -- they are
hard-wired to the breaker panel from the water heater.)

Note that while this provides 240VAC for these higher power
loads, still the maximum voltage above ground is no more than 120VAC.
The lines are 180 degrees out of phase (not a useful phase difference
for starting three-phase motors, but useful for getting double the
voltage to a load while keeping the voltage above ground within reason).
This comment about "180 degrees out of phase" will usually fire up some
who believe that it is a mistatement of facts, but it depends on how you
look at it. :-)

Yes, I see what you mean about 180 degrees out of phase. It works the
same way as those 110 V site transformers we get in the UK (used on
building sites for power tools). They have a grounded centre tap so the
maximum voltage to ground on either line is 55 V. I don't know if you
have these transformers in the US? Possibly not as your supply is
already safer.

It is *very* difficult for the typical city home to get three
phase power, and it is charged at industrial rates. This means that your
whole month is charged as though your highest current drain at any time
during that month was being drawn for the whole month. One person who I
know discovered this to his disadvantage when he fired up a large
heat-treat oven which he acquired surplus. He had three phase, because
he was living in what used to be a commercial shop, and it was still a
machine shop -- he was just living in there. :-)

That's a crazy system of billing. Why does anyone put up with that? I
don't think they bill industrial power like that here.

But -- if you *do* have three phase power, the breaker box has
three buses, arranged in a manner similar to the two bus one for 220V,
except that groups of three breakers make up a full three-phase
connection, groups of two make up a 240V connection, and single ones
*may* be 120V, depending on the service. One common one for use where
120V and three phase are both needed is to ground the center tap of one
of the three phases, which allows two out of three breakers to provide
120VAC. The third one (the "wild leg") produces a much higher voltage,
and should *not* be used for 120V loads. I don't know whether the breaker
panels have a provision for preventing a single breaker from entering
the "wild-leg" slots, or whether they depend on the electrician knowing
what he is doing. :-)

Double breakers can be used in any adjacent pair of slots for
240VAC loads, and triple breakers in any adjacent three slots for three
phase output.

Note that all of the above are delta connections. There are
three phase Wye connections where any single phase to neutral/ground is
120VAC, and between any two phases is 208VAC IIRC. This is why some
motors are rated for 208V-204V.

So you don't have 415 V line-to-line voltage three phase supplies?

And also note one other difference from the UK -- the power
frequency is 60 Hz, not 50 Hz. (You can get away with a little less
iron in motors and transformers for 60 Hz compared to 50 Hz.

Thanks for all the information. I now know a lot more about the US power
system.

Best wishes,

Chris

In article ,
Christopher Tidy wrote:

[ ... ]

Note that while this provides 240VAC for these higher power
loads, still the maximum voltage above ground is no more than 120VAC.
The lines are 180 degrees out of phase (not a useful phase difference
for starting three-phase motors, but useful for getting double the
voltage to a load while keeping the voltage above ground within reason).
This comment about "180 degrees out of phase" will usually fire up some
who believe that it is a mistatement of facts, but it depends on how you
look at it. :-)

Yes, I see what you mean about 180 degrees out of phase. It works the
same way as those 110 V site transformers we get in the UK (used on
building sites for power tools). They have a grounded centre tap so the
maximum voltage to ground on either line is 55 V. I don't know if you
have these transformers in the US? Possibly not as your supply is
already safer.

I've not seen or heard of their use -- though I normally am not
at building sites. However, observing some as I pass, I think that it
may be more common to run tooling from gasoline engine powered air
compressors, thus eliminating all shock hazards.

It is *very* difficult for the typical city home to get three
phase power, and it is charged at industrial rates. This means that your
whole month is charged as though your highest current drain at any time
during that month was being drawn for the whole month. One person who I
know discovered this to his disadvantage when he fired up a large
heat-treat oven which he acquired surplus. He had three phase, because
he was living in what used to be a commercial shop, and it was still a
machine shop -- he was just living in there. :-)

That's a crazy system of billing. Why does anyone put up with that? I
don't think they bill industrial power like that here.

It may well work for an industrial site which has a predictable
power draw. For a home shop (assuming that you can get three phase), it
makes it very awkward to use a large heat treat oven once every three
months or so. (Enough so that it is more tempting to power the heat
treat oven from a gasoline (petrol) powered generator.

[ ... ]

Note that all of the above are delta connections. There are
three phase Wye connections where any single phase to neutral/ground is
120VAC, and between any two phases is 208VAC IIRC. This is why some
motors are rated for 208V-204V.

So you don't have 415 V line-to-line voltage three phase supplies?

Maybe so in large industrial sites, but not where I have worked
(R&D labs).

And also note one other difference from the UK -- the power
frequency is 60 Hz, not 50 Hz. (You can get away with a little less
iron in motors and transformers for 60 Hz compared to 50 Hz.

Thanks for all the information. I now know a lot more about the US power
system.

I'm sure that there is a lot that I don't know, but you have
what I have absorbed so far.

Enjoy,
DoN.

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