Try the Astrosyn MY103 to start as I have a few of those. Measure the voltage across a light load, say 1k.

The main goal is to see if putting a DC current through the winding is an effective way of using a stepper as a variable brake. And whether induced voltage in other winding tells anything about the load its putting on the driving force.

I need to generate a 'load' of between 5 and 100W at 60rpm approx (6rad/sec), equal to a torque of between 1 and 17Nm (obviously a 1Nm stepper wont do this so final design may involve gearing up with timing belts)

Quote Originally Posted by Jonathan View Post
The last comment in your first post implies the plan might be to try and use the stepper motor as a means to measure torque?

Stepper motors that I can easily test (i.e. they're not attached to a machine) are:
3.0Nm Nema 24, 4.2A/phase (parallel), one from Zapp
1.0Nm Nema 23, 1.4A/phase (parallel), Astrosyn MY103H702.. Quite high (10mH) phase inductance which might actually be useful here.
12.2Nm Nema 34, 6.2A/phase, SY85STH156-6204B

Plan:
- Hold stepper motor shaft in lathe chuck, clamp motor to saddle.
- Lathe induction motor controlled via VFD/gearbox, so can easily set various speeds.
- Got an upto 50V, 20A lab PSU which is plenty...
- Can get (more) exact motor speed from oscilloscope.

Which motor (or motors) would you prefer me to test?
Do you just want the open circuit voltage waveform of the non-powered coil, or the voltage under load (i.e. with a resistor attached)?