At high and constant speed and if you disregard the constant current chopper drive
it might look like a sinus curve. In all other cases such as slow speed and/or with frequent starts
and stops the current will always show the telltale signs of the chopper working. Nothing
sinusoidal in this document for instance: http://www.ti.com/lit/an/snva029b/snva029b.pdf
Anything less than top speed will have distinct flat current levels that jump to another level
at each step. Not a sinus at all unfortunately, it all discrete steps. The actual current also has
contributions from the fact that the rotor (and it's permanent magnets) moving can both take energy
from the magnetic fields or return energy to the windings. Most if not all data sheets show the ideal
case with an unloaded motor, get an oscilloscope and check what happens in the real (and ugly) world.
it might look like a sinus curve. In all other cases such as slow speed and/or with frequent starts
and stops the current will always show the telltale signs of the chopper working. Nothing
sinusoidal in this document for instance: http://www.ti.com/lit/an/snva029b/snva029b.pdf
Anything less than top speed will have distinct flat current levels that jump to another level
at each step. Not a sinus at all unfortunately, it all discrete steps. The actual current also has
contributions from the fact that the rotor (and it's permanent magnets) moving can both take energy
from the magnetic fields or return energy to the windings. Most if not all data sheets show the ideal
case with an unloaded motor, get an oscilloscope and check what happens in the real (and ugly) world.