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Old 02-16-2013, 12:51 PM   #6015 (permalink)
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I finally got some time to work on the EV. Now, the EV won't even roll out of the garage at a low speed. It seems like whatever is happening is getting worse. It *starts* to move and then stops. It rolls a tiny bit, maybe half an inch, before the episode starts happening.
So I took the two cables from the controller off the motor and with the controller on and my hand mechanicaly controlling the pot, I measured the volts going to the motor. It put out way more volts than I expected very quickly. It went from 0 to 90v within a very small movement of the pot arm.
But I took that to mean that the controller was responding appropriately.
So I dropped the motor (easier said than done) and with it firmly secured, I used jumper cables to run 6v to it and then 12v to it from my battery pack. At 6v I could barely stop the motor from turing with my hand. 12v was too much to stop, and it sounded like the RPMs were going up and up if I left the cables attached.
There's nothing obvious out of place on the motor, but I don't have alot of experience looking at electric motors so I could be looking at something that's out of place but I don't know it.
Any suggestions of what I could/should test next and pointers on how to do it?

Originally Posted by jyanof View Post
In both graphs you posted, and all 3 events shown in the graphs, the same thing happens:

1 - motor current tracks the command current at first: notice the blue and red lines are on top of each other at first.
2 - then, motor current falls and matches the battery current (light blue line). also, the pwm line (pink) jumps to 512 which is wide open. these all agree with each other - when the mosfets are full on, the motor current and battery current will be the same

this is very odd behavior, especially considering that the vehicle slows down. in normal driving, you will likely never reach wide open pwm, and if you do, it's at a high speed and high current.

i'd say your controller is working correctly, but something is wrong on the motor end. the controller is outputting power, but it's not going to the motor.

I think you mentioned your battery voltage is something like 120v and the charts show that they're pushing about 100 amps when the event happens, so that's 12 kW that's just going into heat somewhere!

it really sounds like a motor problem, maybe something is shorting the field or rotor winding so you're only energizing one set of windings? or, a loose connection? maybe it's fine at first, but as the motor heats up, things expand and cause something to short out? or, maybe it's speed related?
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