ABSTRACT
This chapter describes an adjustable speed induction motor drive which illustrates the concept of fault tolerance. Adjustable speed motor drives, and in particular vector-controlled alternating current (AC) motor drives, are being increasingly used as mission-critical components in a variety of high-performance automotive applications. In the event of sensor failures, it is desirable that the AC adjustable speed motor system continues to operate, even if under a diminished performance capacity. This is especially important in the high-impact automotive applications where even limp-back operation is preferred over no operation. Control techniques for induction motor drives are well treated in the literature. For high performance Induction motor drive systems over the entire speed range, indirect field oriented current controllers (IFOC) are commonly used. In preparation for developing a smooth transition from sensorless to encoder-based IFOC and vice versa, one should develop a signature detection scheme that will identify the loss of encoder.
