Identifying three phase vs. single phase motor?
 

Someone is offering a Quincy compressor at a reasonable price, but he is
not sure if it is single phase or three phase. I need single phase. The
tag on the motor does not seem to help (he emailed me a close-up photo).
It is dual voltage, 208-230/460. The problem with the tag is that it
has a bunch of numbers, but they are not labeled as to what the numbers
are. :-(

Could I take an ohmmeter and figure it out? I would guess that a three
phase motor would have equal resistance on all three combinations of the
phases, while a single phase with neutral would have different
resistance, probably low between the two hot leads and higher between
hot and neutral. Green should be open relative to all the other wires,
no matter the phase count.

Is there another solution?

Richard


--
http://www.fergusonsculpture.com
Sculptures in copper and other metals

Identifying three phase vs. single phase motor?
 

Richard Ferguson wrote:

Someone is offering a Quincy compressor at a reasonable price, but he is
not sure if it is single phase or three phase. I need single phase. The
tag on the motor does not seem to help (he emailed me a close-up photo).
It is dual voltage, 208-230/460. The problem with the tag is that it
has a bunch of numbers, but they are not labeled as to what the numbers
are. :-(

Could I take an ohmmeter and figure it out? I would guess that a three
phase motor would have equal resistance on all three combinations of the
phases, while a single phase with neutral would have different
resistance, probably low between the two hot leads and higher between
hot and neutral. Green should be open relative to all the other wires,
no matter the phase count.

Is there another solution?

Generally you can look at the motor itself. If no bump on the side it's 3 phase,
if there's a bump on the side for start cap; single phase. Another real good
clue is the number of wires in the pigtail. 2 wires - single phase; 4 wires -
3 phase, 3 wires is indiscriminate but you can check to see if any have very low
ohms to the motor case; if so you can assume that it's a ground wire and thus
there are 2 hot wires so single phase.

Looking a slightly different way; if you buy the machine and guess wrong, you
then have to find a motor of the correct size and you may have to upgrade the
controls. Motors are generally pretty available at varying cost (I got a 5hp
Leeson single phase motor brand new for my Quincy compressor) but the real cost
killer is if you have to upgrade the mag switch, that can cost you several
hundred dollars if you aren't careful.

Grant

Identifying three phase vs. single phase motor?
 

In article ,
says...
Someone is offering a Quincy compressor at a reasonable price, but he is
not sure if it is single phase or three phase. I need single phase. The
tag on the motor does not seem to help (he emailed me a close-up photo).
It is dual voltage, 208-230/460. The problem with the tag is that it
has a bunch of numbers, but they are not labeled as to what the numbers
are. :-(

The voltage ratings indicate in a somewhat roundabout way that this is a
3 phase motor. It'd be possible to have a single phase 460V motor, but
in 30 years working around this sort of stuff I've never run across one.
If it were single phase dual voltage the plate would more likely specify
some variation of 230, 115/230, or 115/208-230, though 5HP 115V motors
are pretty unusual.


Could I take an ohmmeter and figure it out? I would guess that a three
phase motor would have equal resistance on all three combinations of the
phases, while a single phase with neutral would have different
resistance, probably low between the two hot leads and higher between
hot and neutral.

A single phase motor will not have a neutral lead. Once the motor leads
are strapped for the appropriate voltage it'll have two power
connections which may be connected hot-hot or hot-neutral, depending on
the power feed.

A better tell-tale of a single phase motor in this size range is the
presence of a start cap. Unless it's a repulsion/induction motor, in
which case it'll be about 4x the volume of a regular induction motor and
have a commutator and brushes on the end opposite the shaft. A 5HP
repulsion/induction motor would be among the unusual 5HP 115V single
phase motors I alluded to above and makes a great compressor motor.

Ned Simmons

Identifying three phase vs. single phase motor?
 

On Tue, 2 May 2006 11:00:33 -0400, Ned Simmons wrote:
In article ,
says...
Someone is offering a Quincy compressor at a reasonable price, but he is
not sure if it is single phase or three phase. I need single phase. The
tag on the motor does not seem to help (he emailed me a close-up photo).
It is dual voltage, 208-230/460. The problem with the tag is that it
has a bunch of numbers, but they are not labeled as to what the numbers
are. :-(

The voltage ratings indicate in a somewhat roundabout way that this is a
3 phase motor. It'd be possible to have a single phase 460V motor, but
in 30 years working around this sort of stuff I've never run across one.
If it were single phase dual voltage the plate would more likely specify
some variation of 230, 115/230, or 115/208-230, though 5HP 115V motors
are pretty unusual.

They are not that unusual, Baldor makes one such popular motor. I
resold one recently.

I agree with everything else that you said.

i

price of contactors (was, " Identifying three phase vs. singlephase motor?")
 

Ignoramus5749 wrote:


Looking a slightly different way; if you buy the machine and guess wrong, you
then have to find a motor of the correct size and you may have to upgrade the
controls. Motors are generally pretty available at varying cost (I got a 5hp
Leeson single phase motor brand new for my Quincy compressor) but the real cost
killer is if you have to upgrade the mag switch, that can cost you several
hundred dollars if you aren't careful.

Grant


Grant, I respectfully disagree, contactors cost much less than that on
ebay. Example (by far not the best deal)

$15, 5 HP rating at 230v:
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7613210040

some used size 2 starters
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7615551695
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7585506953

Absolutely, no question. However, go buy the right coil and enclosure for any of
those units and you could easily add another $200. I'm speaking from experience
here. I got a Quincy horizontal 2-stage compressor with an ancient 3hp 3ph motor
on it, controls all for 460V. Now a 460V mag switch controlling a 3hp motor is
not very big, plus it had a 460V coil. I wanted the full air output from the
machine, so I wanted to upgrade to 5hp, plus I wanted to switch to single phase
in case I ever wanted to resell it. I found a nice Furnas NEMA size 2½ contactor
for a reasonable price (like one of the prices you cite), bought it, went and
bought a motor, then realized I needed a coil, an enclosure and an AUTO/OFF/HAND
switch, all to fit the Furnas contactor. The tab for those 3 items? Nearly $200!

Sometimes the devil is in the details, and I'm not trying particularly to be
right at all costs here, I just am suggesting that one be fully cognizant of all
the potential costs before starting on a motor swap & reconfiguration.

GWE

Identifying three phase vs. single phase motor?
 

Grainger does not list ANY 115/120 volt capable motors at 5 (real) hp.
That works out to a minimum of 31 amps at 100% effiency, more like 40
amps RUN (not start) current.

Ignoramus5749 wrote:
On Tue, 2 May 2006 11:00:33 -0400, Ned Simmons wrote:

In article ,
says...

Someone is offering a Quincy compressor at a reasonable price, but he is
not sure if it is single phase or three phase. I need single phase. The
tag on the motor does not seem to help (he emailed me a close-up photo).
It is dual voltage, 208-230/460. The problem with the tag is that it
has a bunch of numbers, but they are not labeled as to what the numbers
are. :-(

The voltage ratings indicate in a somewhat roundabout way that this is a
3 phase motor. It'd be possible to have a single phase 460V motor, but
in 30 years working around this sort of stuff I've never run across one.
If it were single phase dual voltage the plate would more likely specify
some variation of 230, 115/230, or 115/208-230, though 5HP 115V motors
are pretty unusual.


They are not that unusual, Baldor makes one such popular motor. I
resold one recently.

I agree with everything else that you said.

i

Identifying three phase vs. single phase motor?
 

This is just a guess, maybe somebody will know for su look at the
controller/starter - a 3-phase will have 3 contacts, single phase will
have 2. Bob

Identifying three phase vs. single phase motor?
 

Thanks guys. The start cap on the side seems to be the easiest thing to
see, and this motor is just round, so it must be three phase, and I need
single phase.

The price is not so cheap that I can justify buying it and replacing the
motor and controls.

I think that I am just going to have to buy a new compressor, with a
220V single phase motor. Ingersoll Rand makes the SSL5L5, their low end
5 HP compressor, which I think would meet my needs, basically to run die
grinders at close to 100% duty cycle. It is rated at 18 ACFM at 40 psi.

Richard



Richard Ferguson wrote:

Someone is offering a Quincy compressor at a reasonable price, but he is
not sure if it is single phase or three phase. I need single phase. The
tag on the motor does not seem to help (he emailed me a close-up photo).
It is dual voltage, 208-230/460. The problem with the tag is that it
has a bunch of numbers, but they are not labeled as to what the numbers
are. :-(

Could I take an ohmmeter and figure it out? I would guess that a three
phase motor would have equal resistance on all three combinations of the
phases, while a single phase with neutral would have different
resistance, probably low between the two hot leads and higher between
hot and neutral. Green should be open relative to all the other wires,
no matter the phase count.

Is there another solution?

Richard




--
http://www.fergusonsculpture.com
Sculptures in copper and other metals

Identifying three phase vs. single phase motor?
 

On Tue, 02 May 2006 20:17:52 GMT, Richard Ferguson wrote:
Thanks guys. The start cap on the side seems to be the easiest thing to
see, and this motor is just round, so it must be three phase, and I need
single phase.

The price is not so cheap that I can justify buying it and replacing the
motor and controls.

Good thinking, but giving giving the owner an offer that si
acceptable to you.

I think that I am just going to have to buy a new compressor, with a
220V single phase motor. Ingersoll Rand makes the SSL5L5, their low end
5 HP compressor, which I think would meet my needs, basically to run die
grinders at close to 100% duty cycle. It is rated at 18 ACFM at 40 psi.

I would not give up on the idea of finding a good used deal, too quickly.

i

Richard



Richard Ferguson wrote:

Someone is offering a Quincy compressor at a reasonable price, but he is
not sure if it is single phase or three phase. I need single phase. The
tag on the motor does not seem to help (he emailed me a close-up photo).
It is dual voltage, 208-230/460. The problem with the tag is that it
has a bunch of numbers, but they are not labeled as to what the numbers
are. :-(

Could I take an ohmmeter and figure it out? I would guess that a three
phase motor would have equal resistance on all three combinations of the
phases, while a single phase with neutral would have different
resistance, probably low between the two hot leads and higher between
hot and neutral. Green should be open relative to all the other wires,
no matter the phase count.

Is there another solution?

Richard

price of contactors (was, " Identifying three phase vs. single phase motor?")
 

On Tue, 02 May 2006 08:59:09 -0700, Grant Erwin wrote:
Ignoramus5749 wrote:


Looking a slightly different way; if you buy the machine and guess wrong, you
then have to find a motor of the correct size and you may have to upgrade the
controls. Motors are generally pretty available at varying cost (I got a 5hp
Leeson single phase motor brand new for my Quincy compressor) but the real cost
killer is if you have to upgrade the mag switch, that can cost you several
hundred dollars if you aren't careful.

Grant


Grant, I respectfully disagree, contactors cost much less than that on
ebay. Example (by far not the best deal)

$15, 5 HP rating at 230v:
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7613210040

some used size 2 starters
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7615551695
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7585506953

Absolutely, no question. However, go buy the right coil and enclosure for any of
those units and you could easily add another $200. I'm speaking from experience
here. I got a Quincy horizontal 2-stage compressor with an ancient 3hp 3ph motor
on it, controls all for 460V. Now a 460V mag switch controlling a 3hp motor is
not very big, plus it had a 460V coil. I wanted the full air output from the
machine, so I wanted to upgrade to 5hp, plus I wanted to switch to single phase
in case I ever wanted to resell it. I found a nice Furnas NEMA size 2½ contactor
for a reasonable price (like one of the prices you cite), bought it, went and
bought a motor, then realized I needed a coil, an enclosure and an AUTO/OFF/HAND
switch, all to fit the Furnas contactor. The tab for those 3 items? Nearly $200!

Sometimes the devil is in the details, and I'm not trying particularly to be
right at all costs here, I just am suggesting that one be fully cognizant of all
the potential costs before starting on a motor swap & reconfiguration.

Yes, the other stuff adds up also...

i

Identifying three phase vs. single phase motor?
 

Richard Ferguson wrote:

Thanks guys. The start cap on the side seems to be the easiest thing to
see, and this motor is just round, so it must be three phase, and I need
single phase.

The price is not so cheap that I can justify buying it and replacing the
motor and controls.

So what *is* the price, Richard? If you're going to pass on it you have no
vested interest in keeping it private anymore.

Grant

I think that I am just going to have to buy a new compressor, with a
220V single phase motor. Ingersoll Rand makes the SSL5L5, their low end
5 HP compressor, which I think would meet my needs, basically to run die
grinders at close to 100% duty cycle. It is rated at 18 ACFM at 40 psi.

Richard



Richard Ferguson wrote:

Someone is offering a Quincy compressor at a reasonable price, but he
is not sure if it is single phase or three phase. I need single phase.
The tag on the motor does not seem to help (he emailed me a close-up
photo). It is dual voltage, 208-230/460. The problem with the tag is
that it has a bunch of numbers, but they are not labeled as to what
the numbers are. :-(

Could I take an ohmmeter and figure it out? I would guess that a
three phase motor would have equal resistance on all three
combinations of the phases, while a single phase with neutral would
have different resistance, probably low between the two hot leads and
higher between hot and neutral. Green should be open relative to all
the other wires, no matter the phase count.

Is there another solution?

Richard

Identifying three phase vs. single phase motor?
 

Grant Erwin wrote:

So what *is* the price, Richard? If you're going to pass on it you have
no vested interest in keeping it private anymore.

Grant



He is asking $750. I think that it is a 5 hp two stage, looks
relatively new. This is in Denver.

Richard

Identifying three phase vs. single phase motor?
 

Ignoramus5749 wrote:
...
http://cgi.ebay.com/ebaymotors/Quinc...spagenameZWDVW

5hp, *single stage". I would have thought that getting into the 5hp
size would mean 2 stage. But I suppose that for a given power, a single
stage will give more cfm at a lower pressure. I.e., a 2 stage is only
needed for higher pressures. Yes?

Bob

Identifying three phase vs. single phase motor?
 

I have one of those compressors, I think, though the compressor and
motor are reversed on my unit - If it really is the same, mine will
put out about 20 CFM at 160 PSI sustained.

On Wed, 03 May 2006 13:02:41 -0400, Bob Engelhardt
wrote:

Ignoramus5749 wrote:
...
http://cgi.ebay.com/ebaymotors/Quinc...spagenameZWDVW

5hp, *single stage". I would have thought that getting into the 5hp
size would mean 2 stage. But I suppose that for a given power, a single
stage will give more cfm at a lower pressure. I.e., a 2 stage is only
needed for higher pressures. Yes?

Bob
Bill

www.wbnoble.com

to contact me, do not reply to this message,
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