Missing motor lead numbers.

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Each phase is made of two coils that can be connected in series or parallel, like a dual-voltage transformer, right?

If you energize each polarity-known coil with, say, a 12v transformer, and place the polarity-unknown coil in series with it (like an auto-transformer), couldn't the result, either 24v or 0v, tell you the polarity of the unknown coil?
 
LarryFine said:
Each phase is made of two coils that can be connected in series or parallel, like a dual-voltage transformer, right?

If you energize each polarity-known coil with, say, a 12v transformer, and place the polarity-unknown coil in series with it (like an auto-transformer), couldn't the result, either 24v or 0v, tell you the polarity of the unknown coil?
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Larry, the math does not work out perfectly - but what you suggest is spot on.

One reason it does not work out perfect is that you do not have access to the mid point of the inner Y. It's a 9 lead motor and not 12, so they don't bring that inner connection out. So if you energize, for example, leads 7 and 9 you share only half your voltage with any one inner winding. And the magnetic "coupling" is not totally efficient either to the 3 outside windings. But fundamentally what you suggest does work well enough to figure it all out. In one example on the web, the user supplies 120 VAC (temporarily) to 7-9 and measures ~10V induced across the 1-4 and 3-6 windings. In this manner you can find the 2-5 winding since it's coupled very little to the 7-9 pair (it actually measured out at ~ 1.5V in his video).

Then, like you suggested, he jumpers 6 and 9 to make an autotransformer on that leg and measures the additive 130V across 3-7. Then moves the jumper to 3-9 and measures the subtractive 110V across 6-7.

As you suggested - I'd be more comfortable first tying this with a 12 or 24 volt doorbell transformer, rather than 120 VAC, as long as the doorbell xfmr had enough va to create measurable readings (it might not). His 120 VAC test I assume would start heating up the stator if accidentally left on too long?
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People do essentially the same thing with a 6V battery but I guess there it helps to have a "galvanometer" or an old analog meter to read the direction of needle deflection. As you hit 7-9 with the battery and create a magnetic field, you can tell the polarity of the 1-4 coil by watching the direction of the deflection. No need to jumper the windings to create the autotransformer.

Incidentally, the screenshot above is from this video - it's 30 minutes long but is nicely detailed. His on screen interactive drawing skills are pretty good!

Ethan - glad it worked out for you!
 
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A little late here but another trick is that some manufacturers hide a second set of labels deep in the motor. Take the peckerhead off and remove any rubber or fiber board blocking the guts of the motor and if they are there they will be behind it.
 
And I tested it and it fired right up and purred like a kitten. Elevator guy was being overly dramatic said motor needed to be replaced or rewound. Some of the leads were only about an inch shorter than the others. I'm curious how much I saved the client telling him I could get it wired up 🤔
 
Better yet, use a doorbell or Lionel-train transformer to apply 10 volts AC.
Now you have steady-stage voltages you can measure, very little current, and no risk.
Then it's just simple vector math.
 
MD Automation said:
... True to your word... you are thinking about that Lionel SDS again! ...
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Mea culpa. Can't possibly explain why I became a railfan, except maybe that the family has had Lionel trains since before I was born; I grew up within walking distance of the Chicago, Burlington & Quincy, the Indiana Harbor Belt, and Electro-Motive Diesel; my dad and a whole bunch of neighbors & relatives worked at EMD; I never missed an open house, and my all-time favorite engine is the EMD 567. (Not that I might be the kind of ME geek who HAS an all-time favorite engine in the first place ... )

And speaking of not being a geek ... I'm going to go out on a limb here and suggest that a Lionel-train transformer used for testing an unknown/unlabeled motor qualifies as temporary wiring and need not be configured as a SDS ... or grounded at all.
 
drcampbell said:
... my dad and a whole bunch of neighbors & relatives worked at EMD; I never missed an open house, and my all-time favorite engine is the EMD 567. (Not that I might be the kind of ME geek who HAS an all-time favorite engine in the first place ... )
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Was that at the McCook location near LaGrange, IL?
 
electrofelon said:
😥 Looks like they are saying 10 inches at home. I'm an hour west of Albany. But, I am in Seattle currently!

I got it figured out. After taking the motor out and the peckerhead off, I was able to make out most of the numbers. The only ones I wasn't sure of were 1and 7 but they go together anyway.
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I'm just west of you, had well over 2ft of the white stuff overnight, roads were shut down for a while, you're better off out there today.
 
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