Online converter fed induction motor impulse response identification and parameter extraction using pseudorandom modified PWM

This paper explains how the electrical impulse response of a VSI fed induction motor can be extracted online from normal working data if the normal PWM signals are slightly modified to introduce a small pseudorandom binary sequence (PRBS). It also explains how generic templates can be fitted to the measured impulse responses to obtain adaptive estimates of electrical motor parameters. Simulated and measured results show good online stator resistance estimation, under various quasi steady state loads from standstill to full speed, suitable for applications such as sensorless thermal condition monitoring and protection. The paper also briefly discusses future application of this method to obtain other motor parameters and signatures useful for electrical and mechanical condition monitoring, and possible implementations for line operated machines equipped with standard soft-starter hardware.