I am programming a motor controller where I have to specify the run current (coil peak current) and hold current (coil hold current) of the motors. The motor I used is a bipolar stepper motor, with a whopping 1.86Kg/cm of stall torque at 1.5Amp current (0.75A per winding) at 1.8 degree stepping angle.
However, the table in the specification makes me confused: It lists a different current for a different torque.
Here is a link to that motor controller.
How could I determine run current and hold current from this specification?
Best Answer
To determine the current you need, you first have to know the torque you need. That is a function of the external system that only you know. Once you know the torque you look in the table and see what current is required to generate that torque. If you can tolerate a lower torque for holding versus moving, then you can have a lower hold current than run current.
Keep in mind that motion inevitably eats up some torque due to friction, which actually helps for the holding case. The back EMF of the motor will also reduce the apparent voltage applied to the windings as a function of speed. Stepper motors are rather inefficient, so their back EMF is usually not that big. You can measure it yourself by looking at the open circuit voltage when mechanically spinning the motor at a known speed. That's how much less voltage the motor "sees" at that speed than what you apply.