Modelling and dynamic performance of variable-frequency-fed induction motors

The authors present a transfer-function representation of a variable-frequency-fed induction motor based on a linearised mathematical model. Small changes in speed or electromagnetic torque are related to small changes in input voltage, frequency and load torque. The transfer functions enable step responses to be computed for sudden step changes in input voltage, frequency and load torque. Variation of the instant of step change varies the transient peak. This variation is examined and the peak transients are computed. The transfer-function representation presented provides the basis of transient analysis of a variable-speed AC-induction-motor drive