Resisting Voltage from Power Stage

Hi all,

I have a power stage proving power to a stepper motor.

[ftp.phytron.de]

This power stage, the MSD Mini Powerpack 172-140, outputs a constant 140V DC, with no user-friendly way to reduce it. My motor has a run current of 10A/phase, so I have the drive current potentiometer set for 10.2A. It has a maximum operating voltage of 120V DC (hence my problem). It is an 8-lead, 2-phase motor, wired in parallel. Pins 1 & 2 on the power stage are for phase 1 and pins 3 & 4 are for phase 2. My question is how to reduce the voltage from 140V DC to 120V DC (or a little less). My guess is that I need a resistor on each phase, rated for at least 1,400W, and at most 12 Ohms. I'm just unsure of where to place the resistors. Any help would be greatly appreciated. Thanks.

Stepper motors' torque specs are based on current, not voltage. The voltage value is simply the current x winding resistance. The current you set in the driver is the average value that will be delivered to the motor. You should not have to drop the voltage from the driver/power supply. As long as you set the current within the motor's spec, and as long as the supply is rated for higher voltage than the motor, it will be OK.

With smaller, lower voltage motors it is common to run the motor at 8-20X the voltage rating of the motor.

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Quote
sullivnc

This power stage, the MSD Mini Powerpack 172-140, outputs a constant 140V DC

In fact it doesn't, it will supply up to 140V, but less if the current limit is reached.

Your motor will run fine with a current limit set at 10A.

Edited 1 time(s). Last edit at 05/25/2016 03:08PM by bobc.

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