Phase short to HUB ? - Overcooked

Pskin132

100 mW
Joined
Aug 6, 2022
Messages
39
Hi guys,

I'm wondering if you can help me.

My e-bike wheel is very hard to turn ( controllers disconnected, tested all phases between + & - on controller all are fine; also all the phase wires at the connect end are not touching... still hard to turn.

It cooked from the inside. Is the motor toast or can I test for a short between phase wires and hub motor. If so how do I do that ?
 

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Simple answer, you already identified that you have a short since there is resistance when turning the motor.

Windings look blackened, do they smell burnt? If so, the motor is cooked alright.

You’ve got a bare wire right in the middle of that picture it seems.. might want to start with putting some heat shrink on that.
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There are broken wires in the bottom of the picture too.
E06A5219-3F7A-4635-9062-E794B3B9E33F.jpeg
 
Hi,

For the exposed wire some fireproof sleeve just fell off that I've put to one side.

It does smell a little funny yes. Where would the short be ? I wanted to try remove the short "if possible" and try it. The short doesn't seem to in the wiring cable harness.

Is there a phase test at the hub motor I can do ?
 
Almost certainly the windings themselves are shorted directly to the stator laminations and to each other (because the insulation has been burned off).

Repairing this requires rewinding the entire motor; it's more cost-effective to just buy a new one, since it is possible the magnets got so hot that they are no longer as strong as they were, so the motor wouldn't have the same torque capability it used to even if you rewound it.


You can use a multimeter on diode test or 200ohms, with the red probe on the barest metal you can find of the stator laminations, and the black probe on any one of the phase wires or the Y-tie point (the bare soldered twisted wires). If you get a reading of anything other than "infinite" (whatever your meter displays for that) then there is a short of that value on one or more of the phase wires to the stator.

You can't test the resistance of each phase to the other phases, because of that Y-tie point, they're all basically one wire as far as your meter is concerned (unless you have a really good (expensive) meter that can test millohms or microohms ;) ).

But...it's not really worth even testing it.


BTW, a phase short often blows up FETs in the controller, so you will most likely also need a new controller as well. So it is probably worth buying a whole kit with motor and controller together. :/
 
Yeah that motor is completely toast.
In theory you could rewind it, but in practice it is very difficult so you can forget the idea unless you're willing to put a whole lot of time and effort in learning how to do it.

It's time for a new motor!
 
The motor windings in the OP photo look severely burned up.
If hub will not spin freely (with motor cable unplugged from controller) this confirms the motor windings themselves have shorted out internally from overheating.
The shorted coils act like a magnetic brake. If you rotate the hub very very slowly it will turn, but as you increase the rotation speed there will be more and more drag. Again: drag which increases with faster rotation confirms shorted stator windings.

It is possible (but tedious) to rewind a hub motor if it is in good condition mechanically (all magnets still in place and good bearings). However, rewinding is a lengthy and precise project, as another person posted. Each coil must have the correct number of turns and be positioned exactly like the original coil. You must start unwinding with the coil which isn’t underneath any other coils. Count the turns while unwinding it. Take plenty of photos and make your own diagram. Note how each coil is connected to the other coils. Then repeat unwinding every other coil until the stator is empty.
 
Could be the insulated phase wire melted inside the hub, where it goes from the motor windings to the phase wire, if the phase go overtop one another inside the hub. Happened to me once, tell tale sign was the cogging on the dd.
 
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