Alan B
100 GW
I was looking at some different configurations for BLDC motor controllers and wondering if a different configuration would be an improvement in a useful way on ebike applications. Here's one short paper that shows several topologies:
http://www.ijitee.org/attachments/File/v2i1/A0355112112.pdf
It looks to me like a motor controller made with a buck type current source feeding the commutating inverter (Buck-CSI config) would have some useful advantages, especially for a homebrew controller. The PWM is confined to the buck stage and it can have a much higher quality and lower loss coil (than the ones in the motor). It can be operated at a much higher frequency which makes the input capacitors much smaller, and the coil much smaller. There is a single place to measure phase current. Shoot through events are current limited on the commutation FETs, and they can be switched at the commutation rate which potentially simplifies their drive. Either Trapezoidal or Sine can be implemented, though Sine puts more requirements on commutation FET switching. Phase current throttle feedback becomes much simpler. dV/dT on motor windings goes away as motor sees only DC, and a lot of the noise and EMI go away, what is left is confined to a small volume inside the controller. This configuration would also drive a low inductance motor nicely.
http://www.ijitee.org/attachments/File/v2i1/A0355112112.pdf
It looks to me like a motor controller made with a buck type current source feeding the commutating inverter (Buck-CSI config) would have some useful advantages, especially for a homebrew controller. The PWM is confined to the buck stage and it can have a much higher quality and lower loss coil (than the ones in the motor). It can be operated at a much higher frequency which makes the input capacitors much smaller, and the coil much smaller. There is a single place to measure phase current. Shoot through events are current limited on the commutation FETs, and they can be switched at the commutation rate which potentially simplifies their drive. Either Trapezoidal or Sine can be implemented, though Sine puts more requirements on commutation FET switching. Phase current throttle feedback becomes much simpler. dV/dT on motor windings goes away as motor sees only DC, and a lot of the noise and EMI go away, what is left is confined to a small volume inside the controller. This configuration would also drive a low inductance motor nicely.