Setting Drive Amperage

[mshaker]

Greetings;

How do I determine the Amperage to set the Drives?


I have:

A 50V 12 Amp Power Supply.

CW250 Drives, that can be set between 1.5 and 5 Amps in .5 Amp steps, using dipswitches.

Steppers that are rated 3VDC/.42ohms.
(3V/ 1.8Deg. SHINANO STEP MOTOR-MPJA, Inc.)


I was told to set them at 5 Amps. Everything is working, but the Steppers get real hot real fast. After only 1 minute of operation, I can only hold on to a Stepper for about 2 seconds.


Thanks for your help!


- Mark

[mshaker]

Hmm... no replies... How about tackling my problem by trail and error?

What happens if the Drive's Amps are set to low?
(No movement? Missed steps?)

What happens if the Drive's Amps are set too high?
(Will the motor or drive fail?)

Thanks for your help!

- Mark

[kreutz]

Hello;

It all depends on the stepper motor used and the controller features. It is common for a stepper motor to reach temperatures as high as 85 degrees centigrades in normal use. That doesn't mean that you should work at those temperatures.
Your motors are rated for 7 amps (3volts/.42 ohms) as per your statement. You can make them work cooler if you drop the power supply voltage to about 30 to 40 volts. You can also reduce the motor current if the torque you have, at reduced currents, is enough for your machine. Some controllers reduce the current on standby in order to keep the motors cooler.
Too low current will give you missed steps due to lower torque. All stepper motors have a torque curve that decrease with the rotational speed (RPMs), after some RPM value the torque vs rpm curve's slope will be higher. Higher power supply voltage will move that point toward the higher RPMs but will increase the motor and controller heating.

Best regards,

Kreutz.

[mshaker]

Kreutz;

Thank you.

I didn't know the simple Amp = Volts/Ohms formula, so now I feel better about my set-up.

My Power Supply output is fixed, so for the moment I'll play with the Drive's current.
I've set them at 3 Amps, and the steppers do seem to run cooler. If in testing they perform well I'll keep them there, if not, I'll up the Amperage.

- Mark