How does the motor/accelerator pedal work?

[Nick]

Driving my 2016 SEL I have started to wonder how the motor speed and torque are controlled. My simple concept is that the speed (RPM) of a DC motor is more-or-less proportional to voltage and the torque proportional to the amps, but this is obviously naive. The e-Golf speed varies over a wide range, while the battery is at a more-or-less constant voltage. The simple way to reduce the current or voltage would be with a resistor or voltage divider, but that would be very inefficient. I'd appreciate an explanation of how this is achieved efficiently and continuously on an EV.

Thanks

 

[f1geek]

All EVs have a power electronics module that converts DC power from the battery to AC power to make the motor turn. I don’t know the electrical details but I’m sure you could research EV AC motor controllers to try to understand. I bet EV West sells them.

 

[JoulesThief]

I would suspect that the accelerator is Pulse Width Modulation based.

 

[GadgetGav]

EV drivetrains use AC induction motors, first invented by Nikola Tesla (hence Musk's company's name).
There are no permanent magnets - instead the rotor sits in a ring of electromagnets. The speed with which the rotor rotates is determined by the frequency of the AC supplied to the electromagnets (hence why you hear a rising whine in some EV powertrains as you speed up).
The variable induction is also what allows variable regenerative braking from the motor.

Basic explanation is here:
https://www.explainthatstuff.com/induction-motors.html

 

[f1geek]

A few EV drivetrains use AC induction motors (rear motor of current Model S, X and Audi e-Tron). The vast majority use permanent magnet AC motors such as the Tesla Model 3, front motor of current Tesla S and X (Raven powertrain), Leaf, e-Golf, Bolt EV, Volt, Kia Niro, Hyundai Ioniq and Kona, Porsche Taycan, Fiat 500e, Jaguar I-Pace, BMW i3 and i8, and on and on.

More info from BMW about using magnets in their AC motors:

http://hybridfordonscentrum.se/wp-content/uploads/2014/05/20140404_BMW.pdf