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# Does the resistance of cable leading to the steppers add to Rm?

Associate II

I'm currently tuning my PowerSTEP01 based system for voltage control and I somehow measured a bigger DC resistance on the motor phases than stated in the motors datasheet. Then it came to my mind that this could be caused by the cable used to connect the stepper motor.

Indeed, when I calculate the resistance of the cables, I get ~350mOhm for my system. For example, one of the motors has an internal phase resistance of 900mOhm, which means that the cables leading to the motor add ~30% to the overall phase resistance.

Is my assumption correct, that the cable resistance should go into the calculation of the stepper driver parameters?

1 ACCEPTED SOLUTION

Accepted Solutions
ST Employee

Hello @Alex Rössler​,

in voltage mode driving the powerSTEP01 controls the phase current applying a sinusoidal voltage to motor windings.

Phase current amplitude is not directly controlled but depends on phase voltage amplitude, load torque, motor electrical characteristics and rotation speed.

In your application, the cable resistance value is comparable to that of the motor windings. So you can consider an higher winding resistance.

It will be necessary to apply a higher voltage to obtain the same phase current of theoretical calculation with only motor parametrs.

Let me know if these info are useful, if yes please "Select as Best" button to close the topic.

ST Employee

Hello @Alex Rössler​,

in voltage mode driving the powerSTEP01 controls the phase current applying a sinusoidal voltage to motor windings.

Phase current amplitude is not directly controlled but depends on phase voltage amplitude, load torque, motor electrical characteristics and rotation speed.

In your application, the cable resistance value is comparable to that of the motor windings. So you can consider an higher winding resistance.

It will be necessary to apply a higher voltage to obtain the same phase current of theoretical calculation with only motor parametrs.

Let me know if these info are useful, if yes please "Select as Best" button to close the topic.