This paper deals with the selected methods of detecting angular misalignment in drive systems with a permanent magnet synchronous motor (PMSM), which are based on the analysis of the stator phase current signal, as well as their experimental verification and comparison. The proposed and compared methods are spectral analysis and wavelet analysis of the stator current, stator current envelope, stator current space vector module. Furthermore, the influence of power supply frequency and load torque on the performance of the proposed diagnostic methods is also discussed. The experimental tests were carried out for an undamaged motor and for two levels of angular misalignment. The article discusses the question of exactly what damage symptoms can be extracted from each of the methods. In the case of spectral analyses, it is demonstrated which multiplicities of the failure frequency are the most sensitive to misalignment and the least sensitive to changes in motor operating condition, which may be considered novel in the case of drive systems with permanent magnet motors. It is also proven that discrete wavelet transform (DWT) of the envelope and monitoring of the value of the relevant components allows the detection of misalignment with the availability of measuring current only in one phase in various motor operating conditions.
The popularity of high-efficiency permanent magnet synchronous motors in drive systems has continued to grow in recent years. Therefore, also the detection of their faults is becoming a very important issue. The most common fault of this type of motor is the stator winding fault. Due to the destructive character of this failure, it is necessary to use fault diagnostic methods that facilitate damage detection in its early stages. This paper presents the effectiveness of spectral and bispectrum analysis application for the detection of stator winding faults in permanent magnet synchronous motors. The analyzed diagnostic signals are stator phase current, stator phase current envelope, and stator phase current space vector module. The proposed solution is experimentally verified during various motor operating conditions. The object of the experimental verification was a 2.5 kW permanent magnet synchronous motor, the construction of which was specially prepared to facilitate inter-turn short circuits modelling. The application of bispectrum analysis discussed so far in the literature has been limited to vibration signals and detecting mechanical damages. There are no papers in the field of motor diagnostic dealing with the bispectrum analysis for stator winding fault detection, especially based on stator phase current signal.
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