This project aims to be an open source torque controller for AC induction motors.
This software runs on an STM32. In addition, the following hardware is required:
- 6 x IGBT or MOSFET
- 6 x Isolated FET drivers
- 3 x Hall effect current sensors
- Rotary encoder
- A large film capacitor
An example schematic can be found here: https://nutty.tk/inverter3.pdf
The software generates a 3-phase output using PWM. The frequency and voltage are adjusted to create a torque proportional to the "throttle" input.
The algorighm is very simple and is based on setting the slip of the motor. The output frequency is the shaft frequency plus a slip, where the slip is proportional to the throttle input. The current is controlled to keep it proportional to the slip (up to the input voltage).
So far this has only been tested up to 1A @ 48VDC on a 250W motor. It is my hope that this should scale to larger builds for electric vehicle use. More experimentation will follow.
My low power test build: https://imgur.com/a/IR173Ng
Previous iterations of this code have implemented FOC, however overall the simple slip based algorithm has produced better results so far.