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Heat up of stepper motor


#1

Hello,
I am using a pololu nema8 motor with a DRV88825 driver in full step mode. The current limit I set a bit lower than the allowed one. I use a power supply which gives 38V (I do not have another one right now, so that’s the reason I take this one).
When using the motor, I actually do not notice a lot of heat produced in the driver. But the motor heats up. Now I am wondering, how much heating up is normal, how much is still okay and what would be too much. I let the motor run several minutes without pause, just changing the rps to try. The motor became “very warm”, but I could still hold it in my hand without having to let go. So for sure it was not above 50-60°C.
Is the temperature of the motor dependand on the voltage of my power supply? Or more on the current limit I set?
Best, Miriam


#2

Hello, Miriam.

How hot the motor gets will be mostly dependent on the current limit setting and the input voltage will not have much affect. It is normal for stepper motors get warm to the point that touching it might be uncomfortable. You should double check that your current limit is less than or equal to the current per phase rating of your motor.

-Derrill


#3

Hello Derrill,
thanks a lot for your answer. That the motors getting warm is normal sounds really good to me.

Just to be sure about the current limit: This is what is given for the driver “Current Limit = VREF × 2” and the current rating per coil for the motor is 600 mA. So when first using the motor I put it a bit lower than 300mA. Last time I set it to about 230mA. That was the setting to which I referred in my post about the temperature.
Could it make any sense to even lower the currentlimit of the driver? Is there any minimum?

Thanks for the help!
Miriam


#4

The current through the motor is directly proportional to the holding torque of the motor, so using a lower current limit will also limit the maximum torque the motor can produce. You can run the stepper motor at a lower current limit as long as it still has enough torque to move your load. The driver itself does not practically have a lower limit for the current limit setting.

-Derrill


#5

Thank you very much for your explanations!
Best,
Miriam