Yes I can see your point, since the current flow through the inductance (motor) is based on time, reducing the time would restrict the total current flow, hence reduce torque.
I think there are two things to consider here, one is the maximum current through the motor in one PWM pulse, the other is the max current over a longer time period with the PWM pulse at a higher ratio. If the PWM ratio is at say 80% the current will go up during the pulse, when the PWM reverses for the 20% it may not reach full current flow in the reverse direction before switching back again, therefore it starts the next pulse with a head start, the current gradually building with each pulse.
Limiting your accelleration will reduce the current build up over a series of pulses by keeping the PWM throttled back, whereas changing either the time period or inductance would change it on a pulse by pulse basis.
I suppose the question comes down to this, does increasing the frequency of the PWM have the same effect as throttling back the PWM over a time period or does it just reduce the current switched on each pulse?
Something to muse over on a long car journey!!!
2sm, if you want to try the variable frequency just send your drive back and I will reprogram it for you, no charge.  |