How do you know if a commercial driver is working with trapezoidal or sinusoidal commutation? If you measure the 3-phase voltage applied to the PMSM by means of an oscilloscope, will you see a difference?

  • $\begingroup$ In a block commutation , the phase shift between each phases is 120degrees. However the diagram of block commutation shows only 60 deg phase shift. Does anybody know if a 60deg phase shift could commutate the BLDC correctly? $\endgroup$ – user11205 Nov 30 '15 at 21:33
  • $\begingroup$ Please start a new thread if you have a new question. $\endgroup$ – Ben Dec 1 '15 at 2:37

I'm reasonably sure that the sinusoidal wave will look like a sign wave, and that the trapezoidal wave will look more square-ish. The image below explains it better:

Trapezoidal vs Sinusoidal waves

| improve this answer | |
  • $\begingroup$ The trapezoidal waveforms don't look right. It is block commutation, which means that for each phase, it is positive for 2 states, tri-state for 1 state, negative for 2 states, and tri-state again for 1. When it is tri-state, the back-EMF varies so that it looks trapezoidal. Your diagram seems to show the $V_A$ at max for only 1 commutation state in each cycle $\endgroup$ – ronalchn Jun 19 '13 at 12:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.