Re: [CAD_CAM_EDM_DRO] Bipolar stepper driver for unipolar steppers

> While I understand that the voltage drop of the motors would double because
> of the increased winding resistance, I don't understand why the current
> would halve IF the motors were driven by a constant current source. Would
> you not maintain the same current as long as the open circuit voltage could
> support it and take advantage of increased torque? I realize that this
> increase would come at the expense of top speed due to the inductance, as
> you mention. Could you explain a little bit more?

If you run the rated current for normal half-winding operation through
the full winding you will create a magnetic field nearly twice as
strong as the designer intended. This creates greater torque, but
risks demagnetizing the permanent magnets. It also doubles the
heating. So you must derate the current to use it this way. I don't
know the safe derating percentage - it is not 50%, so you can get very
slightly more torque this way, but generally folks seem to be
recommending that motors be run in the lower inductance half-coil
mode.

The motor you have is already high resistance, which probably means
high inductance as well - so I would strongly suggest the half coil
configuration so that you can get decent performance with the maximum
supply voltage your drives can handle.

Chris