# building a controller for shunt motor



## DavidDymaxion (Dec 1, 2008)

The motor does not get a constant 72V, that would lead to starting with a huge jerk that might even break things or melt things. You need to PWM the voltage on the field and armature separately. Simple control would be to have the field be some fraction of the armature pwm -- then the motor would act alot like a series motor. Varying the field off of this simple ratio can give better torque and better regen. Once the armature is maxed out (100% pwm), weakening the field can allow the motor to continue to speed up. Overdo the field weakening, though, and you can destroy the motor. Overdo the field PWM, and you can overheat the windings.

Search for "field map" on this board for some of Major's tips on characterizing a sepex motor, to help figure out how to control it.


cheever said:


> I'm building a controller for a 72V General Electric shunt motor. It's for a GEM car owned by my school. The original controller died so it became my senior design project to make a new one. I'm looking for any good resources to get the ball rolling.
> 
> From what I understand I need to use pwm to control the speed and that the 72V is constant to the motor.
> 
> Thanks for the tips!


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