A robust sensorless fault diagnosis algorithm for low cost motor drives

This paper presents a sensorless fault diagnosis technique for low cost AC drives. Currently, in order to achieve a reliable fault diagnosis, a high resolution speed sensor is employed to measure the frequencies of fault signature which depends on motor shaft speed. There is an increased tendency toward sensorless control of AC motor drives because of mounting problems, associated cost, etc. Therefore, the speed sensors become less common feedback tools in high performance motor control applications. The fault diagnosis becomes quite a challenging task in the absence of information from a speed sensor as highly precise motor speed estimation is needed. In this paper, a simple and efficient algorithm for fault diagnosis is proposed utilizing frequency tracking method which does not require speed sensor feedback. It is explicitly verified that the performance of the proposed algorithm is almost comparable to the cases where an accurate speed sensor is used. The algorithm is derived mathematically and its efficacy is proved experimentally using a 3-hp motor generator setup.