I have a client using a three phase brushless motor driven by H-bridges. I know little about it except that it uses high frequency PWM to generate sinusoidal excitation.
As I see it (and there's no possibility to look on a scope, it's on a different continent) each motor winding must take current as half a sine from one diagonal pair of H-bridge switches, then the next half from the other pair, which means the /supply/ current looks like an upside-down full wave rectified sine.
Add the three phases together and the supply current is the same shape, but three times the frequency and about a quarter the p-p amplitude.
The client thinks there should be no supply ripple.
I think I'm right. Am I?