Control Means for Minimization of Losses in AC and DC Motor Drives

Motor drive losses can be reduced considerably by independently controlling the voltage and frequency for ac motors, and the field current and armature voltage for dc motors for any torque and speed operating point. The quantities to be controlled are already accessible in inverter ac power supplies and phase-controlled rectifier dc power supplies. The control signals can be supplied by an open- loop controller which solves the loss minimization equations using preset drive parameters, or by an optimizing controller that measures or calculates the losses and finds the combination of quantities that minimizes the losses.