MP3 failure - heavy cogging upon rotating by hand

[Revhead]

Hi Forumites,
I've been soaking up the good info off this forum for a year now.  Thanks to all who share their time and knowledge.
Presently I have a laundry full of failed MP2 and 3's, some by stupidity, some for other reasons.
Usually it's controller issues or frayed wires, simple things to deal with.
I'm getting around to fixing them now and have found my first problem that has stumped me.
I have replaced the controller on an MP3 that failed on a customer.  Still no joy.
The motor won't spin under it's own power.  Whether it's powered or not, there's 'lumpy'/ severe cogging when rotating the wheel by hand.
I suspect a failed hall sensor or crossed wires somewhere in the wheel.
How can I further test the wheel to locate the problem?
This wheel needs to be on a customer's bike like yesterday.
Can anybody give me some guidance?
Many thanks

[Lollandster]

You can test the hall sensors if you follow the instructions found here: http://www.goldenmotor.ca/FAQ/questions.php?questionid=95

[Cornelius]

Severe cogging usually means one or more of the phases are shorted; either 2 of the phase wires are shorted, or some of the mosfets on the controller are faulty (shorted).

[Revhead]

Thanks Cornelius and Lollandster
I'll have a look at the phase wires and check the instructions on testing hall sensors  :-)

[GM Canada]

With the controller removed is it still hard to spin?

Gary

[Revhead]

I have now attached a controller and used a 4.5v battery source to place a current across the red and black hall power wires.
When I connect the voltmeter across the red and a hall wire (Y,G,B) and spin the wheel, I get a fluctuating voltage indicating a working hall sensor.  All halls give a similar voltage when tested.
The motor is not cogging now.  It will run only when I spin the wheel to get it started.  This seems classic hall failure but the halls all give current.
The hall plug that fits into the controller seems a little loose but when I ensure a good connection is made, the motor still wont self start when powered.
I'm confused

[Bikemad]

As the motor was cogging before, there must have been a problem with either the controller itself, or a short short between two of the phase wires.

It's possible that one of the phase wire screw connectors could have inadvertently been forced against another phase wire when the controller was fitted. This could allow any sharp edges on the screw to penetrate the insulation on the phase wire resulting in a short circuit between two phases:



Trying to operate the motor with two phase wires shorted could have overloaded the MOSFETs causing one or more of them to fail, which could also explain why the motor is unable to start on its own.
Fitting a controller that is known to work properly would be the easiest way to confirm if it's a controller problem.

Does the motor run evenly, or does it sound a bit irregular when running at very slow rpm?

Alan
 

[Revhead]

Yes I suspect there was a phase wire short.  I'm unable to more accurately narrow down the issue as we have run out of controllers and are waiting for the next delivery of them.
I've tried the only controller we have that I think is ok and all I get is typical behaviour of hall sensor failure, ie the motor won't run till the wheel is manually rotated, then it's fine.
With all my taking things apart and putting them back together, the heavy cogging is no longer happening.
I'm wondering if a faulty controller could cause similar behaviour to a hall sensor failure?

And sorry about the slow reply, the boss and I have been out at a solar/wind powered festival on French Island, Victoria, Oz called Fest la Frog.  We had an electric bike there and got lots of interest.  Someone wants to build a motorised four poster bed using 2 Magic Pies.

Also for a laugh, check out http://festivalcouch.com/         https://www.facebook.com/festivalcouch
Mardy the man behind Festival Couch has fitted a 5kW GM motor to a 3 seater couch and wow can it move!  0 to 47km in 3 seconds and all while going sideways!