Two phase motor wiring?

Hello all

I found an old whasher motor at the junkyard. Its rated 220-240 V, has a starting capacitor and two wires for connection. I asked one of the local washer repairmen how to connect it; he said I have to connect each wire to any one of two legs in the 3 phase outlet I seem to have star (Wye) service here at the house, (the old electric stove was plugged there): 110 V phase to neutral, 208 V between two phases, 208/120 between phases, and between phases and neutral. Three wires only that I can see. Please correct if wrong. Now, can this motor be connected? I dont feel trusty of the advice of that guy. I wonder also at the difference between the voltage rating and the local 3 phase voltages. How could it ever work?

Any advice thanked in advance.

--


Regards,


Mongke
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I don't think "Wye" applies in this instance because it sounds like you have normal house wiring (2 phases + neutral + ground) available in your service panel and not three phase. So, at a 240V outlet you have both phases (2 "hot"). In other words, he told you right (sort of) assuming that you lived in an industrial setting rather than a house...it is still right, but I believe you are getting confused because you don't have a third phase (which you wouldn't be using anyway) available to you. The color coding of the wiring is what you are used to with 120V except you'll note that there is also a red and that is the other "hot" phase.

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You don't have two-phase. And probably don't have three phase. If your motor calls for 220/240 volts, plug it it the same place as the electric stove outlet.

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Right on, Leo. Amazing how this old, tired question keeps cropping up. Bob Swinney

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Amazing how this old, tired question keeps cropping up.

If you're not in Buffalo or Philadelphia, then the motor is most likely not two-phase.

Besides, home appliance motors would always be single-phase, as two-phase (and three-phase) is for commercial or industrial customers.

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On Thu, 24 Jun 2004 05:55:20 +0000, Peter H. wrote:

Yes you're right. The motor is single phase 220V. Initially I misunderstood the meaning of the voltage rating but of course the motor has a starting capacitor, therefore => single phase.

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Mongke
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two-phase

misunderstood

Well not really - the capacitor actually produces a second phase so STRICTLY speaking it is actually two phase albeit running from a single phase source. !!!

Andrew Mawson

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On Wed, 23 Jun 2004 16:54:41 +0000, Leo Lichtman wrote:

Just measured the voltages at the outlet. Any two wires gives 208 V between them. The guys at the local electric store tell me this is "three phase service with three hot legs". I gather this means there are 4 wires for 3 phases and ground, no neutral (?)

--

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Mongke
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On Tue, 22 Jun 2004 23:08:40 -0500, "mongke"

The only way you have 120/208 single-phase (2 hot wires, one Neutral and a safety ground) at a house is if you're in a condominium or other large multiple-occupancy development. They bring in 120/208 Wye 3-phase 4-wire ABC-N into the power room, and feed the first stack of meters from the AB phases, the second BC and the third CA. The House Panel gets all three phases for the elevator(s) and large pumps & motor loads.

If you have 208V power you can run most 240V motors that don't specifically say you can't on the spec plate. They will run a little warm and not have the same torque ratings.

An electric range receptacle is usually 50A 240V (or 30A 240V) and is 2 hots and ground only. This will work perfectly to test the motor - but beware the 50A breaker - that motor will burn up long before the breaker trips.

If you are going to use the motor on something semi-permanent like a power tool, be sure to have a 15A or 20A 240V receptacle installed for the tool and use the proper cord caps, they carry them at most good hardware stores. And put inline slow-blow fuses (or a fused safety switch) between the motor and it's power supply to protect the motor from a locked-rotor condition - don't count on the breaker to protect a small motor, only to save the house wiring.

--<< Bruce >>--

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
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On Wed, 23 Jun 2004 19:25:57 +0000, Bruce L. Bergman wrote:

Just came from checking the outlet. It gives 208 V between any two receptacles. I guess this means I have either "Common 3 Wire 3-Phase" or "Common 4 Wire 3-Phase". BTW, my understanding is that the former type will not allow 110 V loads if one wanted to, because of the lack of a neutral? And that can I connect the motor to any two legs in the outlet?

Yet another thing, the breakers in the panel are wired in such a way that opening one the voltage readout falls to 110 V (phase to neutral?) and opening the next one drops to 0 V. I gather this means there is one breaker each phase. Does this mean that the phase for the open breaker can be used as neutral if there is a need to run 110V stuff?

I will be using the motor for the Gingery lathe, so it's great to know that I must use a safety switch. Probably saved the motor beforehand.

Thanks.

--

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Mongke
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On Wed, 23 Jun 2004 16:47:19 -0500, "mongke"

Where do you live? It would be EXTEMELY unlikely to have 120/208V 3-phase Wye inside a US residence - unless you are on a farm and have one service for everything. Even then, you wouldn't want to wire a stove to three phase, they're meant to run on straight 240 V Single-phase - 2 hot lines with 240V across them (120V to ground), and a safety ground.

Get me any numbers you can see on this stove receptacle - it should be a standard NEMA 6-30R or 6-50R for a range, if it's a 4-pin grounding receptacle (newer houses & all mobile homes) it would be marked NEMA 14-30R or 14-50R.

The U shaped pin on your stove receptacle is supposed to be safety ground - you should read 120V between the two power pins and the ground pin, and 208V or 240V between the two power pins. Anything else, and you have much more serious problems than I can diagnose over the internet - do yourself a huge favor and call a local electrician.

The breaker feeding the stove receptacle is supposed to be a two-pole breaker with a permanent handle-tie so you cannot turn off only one power line at a time. This can cause one breaker to trip and you THINK it's all dead, but there's still 120V on the equipment. Get this corrected ASAP.

The safety switch is many things - it is a fuse point to put in the smaller sized ~10A fuses to properly protect the motor, it's the Safety Lockout device so nobody starts the lathe while you have your arms in the way...

It protects you if another family member turns the breaker (at the main panel in another room) back on while you're fixing something electrical inside it. ("The kitchen outlet tripped, better flip every one of them off and on to make sure I find it...") Even at home, get into the habit of Lockout/Tagout procedures - a simple piece of tape over the breaker and a paper tag can save a life.

It's also a panic switch if the lathe starts spitting sparks and you don't think hitting the machine's off button right now is a good idea.

--<< Bruce >>--

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
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On Thu, 24 Jun 2004 02:57:24 +0000, Bruce L. Bergman wrote:

Bruce, I'm not in the US. The neighborhood I live in was sorta upscalish and built in a semirural setting 25 years ago. We moved in 4 years ago.

The receptacle is 3 pin, all straight. The stove was grounded by means of a wire running from the frame to (I'm guessing, since we had the stove removed before moving in) a screw in the outlet box. The piping for all the original installation is galvanized pipe. This seems to have been pretty much common around here back then.

OK. I will do it.

--

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Mongke
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