Reg-Stepper motor

Coil current dependent on coil resistance and voltage applied.I = V / R.Check:Manually turn shaft.Rotate OK?Ohm out all coils.Iff(Not short self other coils?Not open?Same R?)Then next.Hipot coil to case.Voltage dependent on mfg.Apply step voltage, run motor.Monitor curent.Check bearings.Motor OK.s.e.b. time next question simple.Good luck.Chris

If the shaft turns freely and all windings are the same resistance, it's probably good to go. Overheating can cause windings to burn open or short to one another. The amount of current depends on the method used to drive the motor, but it's limited by the wire gauge of the windings and the amount of cooling available.

A stepper motor is actually a synchronous motor. The current that you use to excite the coils depends on the amount of torque you wnat to generate.

The maximum current through the coils is limited by the resistance of the coils and the amount of heat you can dissiate in the coils before the motor gets too hot to work. This is often limited by the Curie temperature of the magnets in the motor - heat the magnets above their Curiee temperature, and they stop being magnets.

The voltage you have to apply across the mtor coils to drive a given current through the coils depends on the rate at which you are spinning the motor.

A synchronous motor generates back EMF - for a permanent magent motor the back EMF, in volts per radian per second is numerically equal to the torque in newton metres per amp - and its coils have inductance as well as resistance, so you have to apply enough voltage to overcome the back-EMF and drive the desired current through the coil impedance.

It can take a while to understand what a stepper motor is doing. Spiining the motor with an electric drill and measuring the voltages appearing across the coils can be a useful exercise in getting a better understanding of your particular motor.