Faults detection and diagnosis for three phase induction machines

University dissertation from Luleå tekniska universitet

Abstract: Three phase induction motors have been intensively utilized in industrial applications, mainly due to their efficiency and reliability. These motors have good properties such as: increased stability and robustness, durability, large power to weight ratio, low production costs and controllability easiness. The most common faults that could happen in the rotor and the stator are: a) short circuit in stator winding, b) broken rotor bars, c) bearing failures, and d) dynamic or static air gap irregularities. These types of faults, are necessary to be identified and categorized, as soon as possible as they can end up in serious damages if not detected in due time. The aim of this licentiate thesis is to present a model based fault detection and diagnosis schemes for three phase induction motors relying on the Set Membership Identification (SMI) approach. In the proposed scheme proper uncertainty bounds and boundary violation rules have been established for detecting and categorizing the fault occurrences. The novel presented diagnostic and fault detection methods are able to detect and classify two types of induction motor faults: a) broken rotor bars, and b) short circuit in stator winding. As it will be analytically presented in the thesis, during the initialization of the algorithm, the parameters of the healthy induction motor are being identified by the utilization of the Recursive Least Squares, extended by the Set Membership concepts, where corresponding uncertainty bounds are also being recursively being calculated based on the assumed noise levels. In the sequel the proposed bound violation conditions for the fault detection and fault diagnosis are being online evaluated, on the converged identified motor parameters, within a sliding time window. The simulation results have been presented motor performance in healthy and faulty cases such as stator currents, rotor currents, torque, and angular speed of the motor. The efficiency of the proposed scheme has been extended evaluated with simulation studies for the cases of: a) one broken bar fault, b) 2\% short circuit fault, c) multiple number of broken bars.

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