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I have some AC motors with 6 wires each. I only have 2 out of 3 phases available. I will test these motors any way. I know the motors won't work in their best condition and I risk create a short circuit if I don't make the right choice. Suppose the internal wiring is like this

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I'm planning to connect 2 and 5 together, phase A to 1 and 3, phase B to 4 and 6. Will it work?

Jader Dias
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  • It would help to know beyond supposition if this is the actual internal configuration of these motors. What you are showing is a two phase stepper motor with center-tapped windings, not a 3-phase motor winding diagram. – Fiasco Labs May 18 '14 at 03:56
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    I'm voting to close this question as off-topic because it has nothing to do with home improvement. – Daniel Griscom Feb 14 '17 at 18:58

4 Answers4

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Three phase motors need to be fed with three phase power. It has to do with the internal configuration, each power leg must be fed power 120 degrees apart so the created magnetic field spins the rotor.

If you're thinking about using 240V split phase to power this motor, the effecive phase angle between each leg and neutral is 180 degrees out of phase. Expect the motor to stall if it will even begin to spin weakly, not create the proper back EMF, draw high current and release smoke.

If you need to run this motor off of split phase, you need to run it from 240V single phase and use a phase converter that electrically produces three phase power output. Your motor will then run perfectly. There are two types of phase converter, Motor Generator and Static (electronic).

Differences between Split Phase 240VAC and 3-phase 240VAC

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Fiasco Labs
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  • VFDs are very handy if the motor is not huge (huge ones need 3-phase input, commonly) - for relatively small motors, 1 phase in 3 phase out versions are handy, and offer variable speed as well as phase conversion. – Ecnerwal May 18 '14 at 04:03
  • Precisely, you might use one on a 1hp 3-phase house well pump motor, but you're not going to run an 8hp 3-phase irrigation pump with it. – Fiasco Labs May 18 '14 at 04:07
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I think its possible by taking a single phase supply and same phase separated by 4 capacitors to make a rotating flux from four different voltages with phase difference of 90 degree. and we can get a rotating flux which may not be the same as we calculate in a three phase motor 120 f / p. but it will be different. its my theoretical we need to confirm it by an experiment.

sarojkanta

sarojkanta nayak
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  • I have never seen a 3 phase AC motor with only 2 coils it takes 3 coils to run 3 phase in both delta or wye configuration. It could be a stepper but these take pulsating DC in the correct sequence for clockwise and counterclockwise rotation. – Ed Beal Feb 14 '17 at 20:31
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First of all don´t connect them as you said, if the wiring is what you are thinking magnetic fields generated from 1-2 trunk will be opposite to 2-3 trunk, (that means ZERO reactance for both = short circuit)

dou you know wether they got a permanent magnet? ( they would not spin freely and u can check check it by connecting a multimeter or LED on some wires and moving the shaft a bit)

You could tell what were those motor for if you happen to know. Are they small? , are they as washing machines motors? different internal wirings should be not for three phase arquitecture but for different speed or voltage configurations.

You can connect a commonplace three phase motor (there are not two phase) using only one phase, you´ll have to start it by pour own hand (only safe if there is nothing attached to the shaft, otherwise don´t do it)) , the rest of power should appear on the remaining (autogenerated) wires to test the remaining motors, that an only be made as a test and you should check using a 0.25 amper fuse, (or a series 100w lamp if they are small)

jose
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You can use a capacitor to simulate a 3 phase supply but you will have only 75% of the power available. However your motor's windings look more like a stepper motor; for this you need a completely different power supply.

Niall C.
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Dieter Wiehe
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