Re: PowerPro Input Power
Posted: Fri Jul 23, 2021 2:51 pm
That's very clever, syncing the motor speed to the power-line frequency!
My hunch is that you're seeing the variable-reluctance motor controller working to keep the motor torque relatively constant as the motor rotates through it's various pole positions. Variable Reluctance motors are basically stepper motors. Which means that they are simple, rugged, and inexpensive motors, but they require a very sophisticated motor controller in order to run both smoothly and efficiently. This Wikipedia article has a good overview.
VR motors inherently have high torque ripple, meaning that the torque you get from a given winding current varies greatly depending on the rotor position. A sophisticated controller, given rotor-position feedback, can largely compensate for the nonlinear torque curve by varying the winding-current magnitude as a function of the instantaneous motor-pole alignment. I can see that explaining the power-supply input current waveform you measured.
But I don't now why one of the eight current cycles (per motor revolution) would be different from the others.
My hunch is that you're seeing the variable-reluctance motor controller working to keep the motor torque relatively constant as the motor rotates through it's various pole positions. Variable Reluctance motors are basically stepper motors. Which means that they are simple, rugged, and inexpensive motors, but they require a very sophisticated motor controller in order to run both smoothly and efficiently. This Wikipedia article has a good overview.
VR motors inherently have high torque ripple, meaning that the torque you get from a given winding current varies greatly depending on the rotor position. A sophisticated controller, given rotor-position feedback, can largely compensate for the nonlinear torque curve by varying the winding-current magnitude as a function of the instantaneous motor-pole alignment. I can see that explaining the power-supply input current waveform you measured.
But I don't now why one of the eight current cycles (per motor revolution) would be different from the others.