Transfer and Weighting Functions for Variable Frequency Induction Motors

A loaded induction motor's response to small changes in supply frequency may be described in terms of a weighting or transfer function applicable at the given steady-state operating point. An experimental method is described in which the relevant weighting function is found ``on-line'' by disturbing the system with a low level random test signal and cross correlating the appropriate input and output signals. Results obtained by the method are presented and predicted responses are compared with direct observations.