Driving a stepper motor at higher voltages

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- eljainc
  
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posted
15 years ago

Mon, May 12, 2008 7:57 PM

Hello,

I have some low end stepper motors, made by Howard Industries, part number 1-19-4203. They are bipolar stepper motors (2 phases, 4 leads). The Inductunce is 31mH, and the phase resistance is 25 Ohms. I am not sure (can't find the spec for) of the current per phase. I would like to run this motor at a higher voltage. Does anyone know what the maximum voltage might be? I know it does depend on the current ratings. I tentatively have a 1A power supply at 48V. I would not be running this motor for long periods of time (short duty cycle). Would this be a safe undertaking or is there a way to find the max voltage of this motor? I googled and could not find any other specs on this motor.

Thanks Mike

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- Tim Wescott
  
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posted
15 years ago

Mon, May 12, 2008 9:28 PM

Higher voltage than what? Without knowing what they're rated for, your "higher" voltage may be a "lower" one.

Fancy stepper drives control the current through the motor, to insure torque at high speeds even when the motor is generating back EMF.

If I had to use an unrated motor like that, I'd experiment to find the current I could drive through it without making it too hot after it had been sitting there at full current for an hour. I'd aim for about a

50-70 degree C rise above ambient at the motor case, and no nasty smells, smoke, or melted bits.

Remember that power = I^2 R, so each 2x step in current is a 4x step in power.

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Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

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- mike
  
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posted
15 years ago

Mon, May 12, 2008 10:33 PM

Stepper motors run on CURRENT. Ohm's law defines the steady state relationahip between current/volts/ohms/power dissipated in the winding. Depending on your application, you may be more interested in the inductance. When you apply volts, it takes time to ramp (exponential) up the current. It's not unusual to use higher voltage with a current limit to get speed.

Depending on your application, you may have more questions than you are currently aware of...inductor saturation may impose further limits.

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