Motor Coil Current

Just ordering some hardware to experiment some more with SimpleFOC. The stepper I’m looking at has the following specs…

  • Rated Current/phase: 2.8A
  • Phase Resistance: 1.13ohms± 10%

I’m pretty new to SimpleFOC. Normally with a stepper, I’d just use a stepper driver that limits the current for me. If I want to use a 12V PSU, that would give me approximately 10.62A based on the coil resistance. If I can find a driver that’s OK with that current, am I going to burn out the motor coils if I don’t limit the voltage in software or will the FOC algorithm keep the current way below that?

You are right to be cautious. It is possible that you could over cook your motor with too much current unless you limit the current.

It is possible to set voltage limit on driver and motor in simplefoc software to protect from this.

Simplefoc can be run closed loop and open loop. People tend to start with the simpler open loop, a sensible thing to do, however this is where you need to be most cautious as you gain understanding of how your power supply driver and motor behave.

When you switch to closed loop, it tends to use less current (unless stalling).

Tldr. Start with a low voltage limit e.g 1v on driver and 0.5 on the motor and watch for motor or driver getting too warm. Current limiting power supply has saved my drivers a number of times.