I've been tasked with carrying out some design improvements on my company's production floor.
There is a flat belt conveyor assembly line, whose movement forward movement is controlled by a single phase induction motor. Previously the induction motor was directly supplied with single phase/wall outlet AC voltage.
As part of the design improvement, the single phase signal will be supplied to a variable frequency drive, whose output will be fed into the induction motor. The idea is to control speed by changing frequency using VFD as opposed to a constant 60 Hz frequency previously.
My question is with how to estimate the power being consumed by the induction motor. At any time, if the conveyor belt has many items moving through it, this means greater load and the motor has to induce more torque, thus more power consumed?
What I am trying to do is, is to minimize the power consumption of the motor. If the conveyor has few items on it, this means a smaller load on the motor, so the frequency input to the motor will be smaller causing lower motor RPM speed, and this is efficient power wise. Is this correct?
Similarly, if the conveyor has many items moving through it, this is a greater load on the motor, so the frequency input to the motor will be higher causing higher RPM speed. Is this also efficient power-wise?
FYI I'll be controlling the frequency output of the VFD using a microcontroller and I already have that figured out.
I just wanted to know if I have the right idea, and to help understand better how the rotating speed of the shaft and the torque produced due to load, influence the power consumption of the motor.