sasukenebe
Electrical
Hello,
I am working on a variable frequency drive for a three phase ac motor, and when going from a state of DC injection braking (2 of 3 phases being fed DC voltage @ ~1/4 Supply voltage ~200V) to a state of rapid acceleration I get the following attached waveforms. The top signal is the current through one of the phases, while the other three are the PWM hi side outputs (the gate signals of the three high side IGBT's).
My question is whether or not what I am seeing is flyback dissipating through IGBT flyback diodes? I would think that flyback would not be sinusoidal, but I cannot think of what else would cause this odd behavior. I am experiencing a "jolt" when accelerating out of brake, further making me suspect this behavior has something to do with not allowing the stored energy in the inductors to dissipate.
One thing I am wondering is if this behavior could be explained by the PFC module built into the IGBT module. During normal operation there are similar sinusoidal spikes. Also the possibility of oscilloscope noise / ringing has not been ruled out.
Thank you,
Gary
I am working on a variable frequency drive for a three phase ac motor, and when going from a state of DC injection braking (2 of 3 phases being fed DC voltage @ ~1/4 Supply voltage ~200V) to a state of rapid acceleration I get the following attached waveforms. The top signal is the current through one of the phases, while the other three are the PWM hi side outputs (the gate signals of the three high side IGBT's).
My question is whether or not what I am seeing is flyback dissipating through IGBT flyback diodes? I would think that flyback would not be sinusoidal, but I cannot think of what else would cause this odd behavior. I am experiencing a "jolt" when accelerating out of brake, further making me suspect this behavior has something to do with not allowing the stored energy in the inductors to dissipate.
One thing I am wondering is if this behavior could be explained by the PFC module built into the IGBT module. During normal operation there are similar sinusoidal spikes. Also the possibility of oscilloscope noise / ringing has not been ruled out.
Thank you,
Gary