Short circuit between phase wires? Fix?

Benjahmin · May 5, 2019

It's more likely that the controller is damaged. Don't start stripping the motor until you get some more information. Afraid I can't help with detail but others will.

Benjahmin · May 5, 2019

It's very unlikely. Phase windings will be low resistance, it can look like a short if your meter isn't very accurate. Windings are very robust and not polarity sensitive whereas the controller is. There is a way to test the mosfets in the controller, it is far more likely that one or more of these are blown. I don't have the technical experience to advise further.
You need to give details (make and model) of your motor and your controller. It's a bit early on a Sunday and the weather's nice, so you may need to be patient. I'm sure you will get the help you need.

Andy-Mat · May 5, 2019

crazymaster said:
Hello.

I was just changing my controller and by mistake i reversed the battery positive and negative connection.
The controller looks like didnt got any damage - showing all the info on it(LCD3 72V)

BUT the motor is not spinning. After disconnecting from the controller - not spinning again.

I checked the resistance between the 3 phase wires and they are short circuited...

Do you think that it worth opening the motor and do u think that it can be fixed?

As others have said, its most likely that the controller is damaged, as I have never seen one with a safety diode built in to prevent damage. Some good ones may have, but guessing only!
Furthermore, the motor Hall effect sensors (if installed, the motor will probably have 6 or 7 wires going to the motor unit, not just the 3 motor power phases, might also be damaged! But as I have never connected one of them backwards, I cannot be certain of that either way....Its just a thought.
Chinese controllers often do not follow western colour convention on such things as controllers, batteries and motors....Blue for positive and red for negative has been observed before....sadly!!
Not all bike motors have hall effect switches inside.....
The likelihood of damaging the motor itself is quite small I feel....
By the way, there are 3 phase Bike controllers, that do not need a motor with Hall effect sensors to work correctly.....just a thought!!
Best of luck.
Andy
PS. Some bikes have a big fuse somewhere, that might be blown.
PPS. You wrote:- "BUT the motor is not spinning. After disconnecting from the controller - not spinning again. " what did you mean by that, once the controller is disconnected, how could the motor run or spin?????

Nealh · May 5, 2019

If the motor doesn't spin by hand with controller connected then it usually means controller fets are smoked, however if you disconnect the controller and it still doesn't spin by hand then you likely have damage to the motor phase wiring or the motor it self.
Do you have motor halls ?

Reverse polarity usually causes controller component damage.
You can check controller fets.
Disconnect the battery and motor probe between Gnd and each of the three phases also do the same for the Red V+ to phases, all readings should be the same and in the range of about 7 - 15 ohms. Any way out reading means Mosfet blown and poss other controller component damage.

Nealh · May 5, 2019

You won't know until you open the motor then to have a look, whether you have burn/ damage to phase connection or the windings.

Andy-Mat · May 5, 2019

crazymaster said:
I tried to explain that i disconnected the controller and everything from the bike and the result is that the motor cant spin again with moving by hand...

it moves a little bit then stop then again

so forget about the controller the problem is inside the motor, just my question is is it possible to repair it...as i told when i connect multimeter to the phases it shows 0 OHM... so it have short circuit

Possibly the Hall effect sensors are shorted, though how that would affect the motor I have no idea - I am assuming that you have them, not all motors are so fitted, but you haven't told us whether you do or not! The total number of wires going to the motor will help....
But it certainly bodes badly for the motor at this time....Maybe wire insulation has melted?
I am assuming that your do not have a Bosch middle crank motor, that you either have a front or rear wheel motor!!
Perhaps a photo and more detail might help more?
Andy

Nealh · May 5, 2019

I would say you have severe burn out of the phase wiring, it is all blackened, the copper windings you can see appear to be ok.
I think you will have to replace the motor wire complete to see if the motor will work again, the tricky bit is getting the new wire through the axle. Lubing the wire caseing and inner axle will make the job easier and I find butte or spread to be very good for lubing.

Heat in time will damage the wiring and resistance will be very poor.
Also where the phases are pinched tight by the cable tie my guess is they are all fused together here causing the phase short.

vfr400 · May 5, 2019

It's probably shorted in the cable somewhere. those motors are pretty cheap, so probably easier to chuck it and get a replacement.

There's a fair chance that you've blown the shunt and the mosfets in your controller, so test the resistance between the battery wires and the phase wires. If it's duff, get yourself a whole new kit.

Andy-Mat · May 5, 2019

crazymaster said:
i just unsoldered them but still not spinning freely

Make loads of pictures just in case you can correct the fault and need to be reminded how it all goes back together...
Separate all six wires and try the spin test again.
Is this a middle motor or not?
IMHO only, is that the motor is finished....sorry! That looks like severe over heating...
Andy

Short circuit between phase wires? Fix?

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