Hey guys,
I would appreciate your thoughts on this. I have presently implemented 6 PWM schemes to modulate the 2-level 3 phase inverter I am using to control my BLDC motor in a simulation. Those PWM schemes are shown in the figure below
I observed that for (c),(d) the BEMF current flows in the inactive phase winding. This is because the induced BEMF forward biases the body diodes of the MOSFET connected to the leg where the inactive phase winding is connected.
But for (a),(b),(e), and (f) the BEMF current does not flow in the inactive phase. I can not seem to find a logical explanation for it, because with those modulation schemes, it should still flow, but it doesn't.
Though for (e) HPWMLPWM the current flowing in the 2 active phases, during the off state of the PWM, freewheels through the body diodes of the MOSFETS but it also passes through the DC link.
Does anyone know why the BEMF current does not flow in (a),(b),(e), and (f) ?
P.S: I am only swtiching on 2 MOSFETs per time.
