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Presentation at APEC 2008 by Steven Schultz

9920 Views 21 Replies 10 Participants Last post by  tdjvolt
I recently attended the 2008 Applied Power Electronics Conference. Steven Schultz gave a nice presentation that included some details about the Chevy Volt.

Here's a bio of Mr. Schultz:
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There is something wrong with the previous explanation on the way that a 3-phase induction PWM drive operates.

DC does not come directly from the stator of the electric machine. The flux in the air gap ( I will withhold information on the source ) couples with the windings in the stator. Faraday's Law applies here - a magnetic flux induces a current in a conductor that cuts across that flux. This current flows through the inverter bridge of the PWM drive electronics according to the ON or OFF state of the semiconductors (most likely power-type MOSFETs, or other transistors working in a switched mode) Regeneration (braking) is a function of adjusting the conduction trigger angle with respect to the sinusoidal current coming from the traction motor, which is functioning as a generator. The permanant magnet in the rotor provides a source of the time-varying magnetic flux that is being cut by the stator windings.

For ICE gearheads, a good example of the conduction trigger angle function in the motor drive is similar to the advance/retard of a spark ignition system. The power developed from an ICE engine is dependent on the timing of the spark with respect to Top Dead Center (TDC). Too much spark advance and the power impulse trys to run the engine backwards.

In the electric drive, too much advance is going to reverse the power flow back through the inverter bridge and will recharge the battery. This is a good thing.

Braking effort of the electric motor can only be sustained to a point that the drive is capable of transferring power back to the battery (receptivity) or dumped as heat in a breaking resistor. The Volt must still have a service brake for the final stop. (rolling stops - a.k.a. California Stops, will get you a ticket)

Hope that this clears some of the fog.
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