I'm working on a hack of an old pen plotter and I'm running into the first problems with the stepper motor control.
Unfortunately, I could not find a data sheet for my motor.
Here is what I know about it:
Manufacturer: Warner Electric - Marengo IL
Model: SM-024-0035-TG
The label also says "STEPPING MOTOR"
The motor was 6 wires and an encoder with 5 additional wires.
I initially assumed it is unipolar stepper motor. To identify the coils I measured the resistance between the wires and was surprised to found 3 pairs with 4.8 Ohms resistance and no common connection.
Does this mean I have a 3 phase stepper motor?
If so, does anyone have a link on how to operate/drive such a motor, or does somebody know how to drive the motor? All I can find on the net are tutorials on how to operate unipolar and bipolar steppers and I honestly have no idea if a 3 phase stepper even falls under these categories.
3 phase motor will behave like a synchronous BLDC pretty much. As with those a 3-phase bridge is
needed but with open-loop control - you just trundle round the 6 states at will. It may run better
with sinusoidal drive (ie microstepping in stepper-parlance) of course. You'd common one end of
each winding to give a wye config, or loop them for a delta config.
I suspect there aren't many single-IC 3-phase stepper drivers, and most of the nice 2-phase ones
assume and enforce 90 degree phase difference so can't be doubled up.
