3 phase stepper motor – question

Hi everyone,

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.

Thanks a lot!

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.

Hi, if you use this link it will explain that the motor is one designed to run as a stepper or a synchronous motor. ELECTRIC MOTOR ADAPTED FOR BOTH STEPPING AND CONTINUOUS OPERATION - WARNER ELECTRIC BRAKE AND CLUTCH CO,US
The PDF at this location even shows how to drive it in block form.
Tom.. :slight_smile:

Sorry, I’m relatively new to steppers and I have to back up for a sec.

Does this mean I’m right to assume that the motor is a 3-phase (variable reluctance) stepper motor when I have the following resistance measurements ?

yellow brown green red blue orange

yellow X 4.8 — — — —

brown X — — — —

green X 4.8 — —

red X — —

blue X 4.8

orange X

( — = infinite )