Mystery motor (idler phase converter) windings' wiring pattern

[kd1yt]

I will need to create three phase power from my single phase service and will likely try an idler-motor-based rotary converter- and I already have two large 3 phase industrial motors that I've previously been given- but both motors are really old (very clean, just old) and have essentially no markings whatsoever, inside or out. They are huge enough that I expect that they were designed to be usable with either 220 or 440, so I have both multiple phases and multiple windings per phase.

What is the best way to simply, reliably, and safely understand the inter-relations of the wiring for the various multiple windings in one of these motors?

Thanks in advance!

 

[JimDawson]

First I would take a look at the data plate on the motor if available. Then if these are standard 9 lead, 230/460 V, 3 phase motors, then they would be wired like this:

Low Voltage (230V)
Connect motor leads 4-5-6 together
Connect motor leads 1-7 to L1
Connect motor leads 2-8 to L2
Connect motor leads 3-9 to L3


High Voltage (460V)
Connect motor lead 1 to L1
Connect motor lead 2 to L2
Connect motor lead 3 to L3
Connect motor leads 4-7 together
Connect motor leads 5-8 together
Connect motor leads 6-9 together

If there are no data plates, then the best you can hope for is that the wires are numbered, at least that will give you some indication of what they are. If the wires are not numbered and no data plate, then I would be heading to the nearest motor shop for some guidance. I'm not sure to how to figure out the phase relationship with no starting point.

 

[John Hasler]

I'm not sure to how to figure out the phase relationship with no starting point.

I'd sort out the windings with an ohmmeter and then figure out the phasing by applying 12VAC to one winding at a time and looking at the voltage induced in other windings. I couldn't do it remotely, though. I'd have to have my hands on the motor. I've got an old book on armature rewinding that would come in handy for such a problem.

 

[Alan Douglas]

If you parallel the windings for the lower voltage, and use something like a large electric heater in series with the power line to protect against drawing too much current, you ought to be able to start the motor with a pull rope around the shaft (but be sure it can't get caught and wind back up and pull your hand in. Don't wrap the rope around your hand). Or start it with a series capacitor to one of the other phases. Once it's running you can measure the terminal voltages and see if they all make sense (are all balanced).

It's somewhat risky running lash-ups like this with loose wires with 240V on them. You might be able to run it, for testing, at 120V or even less.

 

[JimDawson]

I'd sort out the windings with an ohmmeter and then figure out the phasing by applying 12VAC to one winding at a time and looking at the voltage induced in other windings. I couldn't do it remotely, though. I'd have to have my hands on the motor. I've got an old book on armature rewinding that would come in handy for such a problem.

John, can you provide a link to that procedure or explain it in more detail. I would really like to understand how to do it. I've never run into the problem before, but it would be another nice tool to have in the box.

 

[kd1yt]

First I would take a look at the data plate on the motor if available.
If there are no data plates, then the best you can hope for is that the wires are numbered, at least that will give you some indication of what they are.

Thank you everyone. Neither motor has a data plate, but I will look to see if the wires may be numbered.