Quote:
Originally Posted by e*clipse
The numbers I was calculating were sine waves, phase to neutral, and with my motor, it would be impossible to measure those values. (Actually, I'm not sure if the neutral is connected to ground)
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Most (perhaps all) commercial and industrial induction motors have the frame as a ground point. A High Resistance Ground resistor is connected to the frame or ground on the power transormer, which goes to ground for the building, or ground grid. Measuring the voltage across the ground resistor detects a failure in one of your motors, where one phase has worn through the insulation and has put dangerous voltage on the frame of the motor.
I've been struggling with what to do on a vehicle. It's tough to isolate ALL of the metal on a motor from the car frame. But if you are getting into 300 or 600VDC for a pack, just leaning on the car and touching the motor (or controller, or whatever the worn-through wire is touching) is going to give you a NASTY poke, perhaps a 'you're dead' shock.
There are BMS's that claim to monitor this. I have no experience with them. They'd have to convince me that they know what they are doing.