Inductance of CIMs

[Al Skierkiewicz]

Although this has come up for discussion before, I believe what is of greater importance (effect) is the switching frequency of the bridge vs. the brush/commutator frequency of the motor. The discussion revolves around whether the switching frequency should be less than the commutator contact time at max RPM or significantly higher. At the current 2kHz, I believe that a number of pulses will be applied to a single winding (or pair) per contact. In the case of the FP where there is only three commutator segments, this is easy to achieve. In the Chalupa or the old drill motors, there are significantly more segments. The old speed controllers had a much lower switching frequency which made things a little more difficult for good motor performance. Remember, at full throttle (with a correctly calibrated controller) full DC is applied to the motor, no PWM.