Some basic controller questions

[Mwilhelm10]

Hey guys,

I am new to the CNC scene. I have built a stepper motor controller, using an Atmel micro controller and everything seems to be working how ever motors get very hot. My question is:

1: I am using powermax II motors, wired in unipolar, Po=53, Vs=65 and Is=1.55 per phase. Do i need to current limit my supply ? I am using a 17 V, 6 amp supply. I measured the roil resistance to be 1.5 ohms, there for when the motor is not moving it is going to try and pull a whole heap of current because the the current is no longer alternating there for the reactance in the coil becomes 0 and the coil is purely resistive. Is this correct ? if so how do you guys get around this ?

2: When a motor is stationary do u guys still energise 1 phase to increase holding torque ?

Any help would be great.

Marty.

[NeoMiller]

You should not need all the current when the motor is stationary. You could cut down the current to zero but then you wouldn't have much holding torque so you can reduce the voltage or provide a PWM controlled current.