Effect of Magnets Asymmetry on Stray Magnetic Flux Based Bearing Damage Detection in PMSM

Abstract

In this paper, it is shown that stray magnetic flux is a highly reliable condition monitoring variable which is rich in motor health related information and it is superior to motor current. It is wellknown that the magnetic field distribution in permanent magnet (PM) rotors exhibit asymmetry due to magnet manufacturing process. It is shown that, in addition to the clear characteristic bearing signatures, the magnet imperfections induce multiple new bearing fault signatures in the stray magnetic flux. Different than current, the signatures in stray flux are more immune to noise, consistent and independent of load and speed. It is also shown that the stray flux-based detection method can locate the faulty bearing. To justify the proposed approach, comparative simulations and experiments are carried out on a surface mounted PM synchronous motor (PMSM) and an interior permanent magnet motor (IPM) with outer raceway bearing fault and different degree of magnet field asymmetry.

Fault Diagnosis and Fault-Tolerant Control of PMSM Drives–State of the Art and Future Challenges

“…The change in the flux distribution inside the machine can be visible as additional harmonics in the stator current. Therefore, the basic signals in diagnostics of bearing rolling element are mechanical vibration [116]- [127], noise [119], [128]- [130] and stator current [116], [122], [131]- [138].…”

“…There are also papers in which the authors use other diagnostic signals. Thus, in [138] it is shown that the stray magnetic flux spectrum contains more symptoms indicating a damaged bearing than the current spectrum. The tests were carried out in both open and closed speed loops with different levels of magnetic field asymmetry.…”

“…In order to detect damage to a bearing component, it is necessary to process the measurement signals appropriately. Diagnostic methods used in PMSMs and reported in the literature for stator current signal analysis include: FFT [116], [131], [132], [135]- [137], ZFFT [133], OA [138] and EPVA [122], DWT [134]- [136] and CWT [136]. On the other hand, for mechanical vibration analysis: FFT [116], [117], [120], [121], ENV [117], [120], [121], [127], OA [117], [122], OA for vibration ENV [117], [118], [123]- [126] are used.…”

“…Experimental tests are carried out using artificially modelled damages. Most studies are carried out using physically damaged bearings by cutting, drilling or electrically engraved pitting of the component [117], [120], [121], [125], [127], [129], [138]- [140]. In [116] the faulty bearing was artificially aged by a burning grease process at 200°C during 60 hours and a broken cage.…”

Multi‐Objective Optimization and Analysis of Asymmetric Hybrid‐Magnet Offset Motor for Electric Vehicles

“…Due to the energy and environmental problems, traditional fuel vehicles are constantly changing to electric vehicles, and the automotive industry has a strong demand for electric vehicles, and the drive motor is one of the core components of electric vehicles, and a high-performance drive motor can maximize the driving performance and economic performance of electric vehicles [1][2][3][4]. Therefore, the use of high-efficiency motors is an important direction for the development of electric vehicles [5]. Permanent magnet synchronous motors are widely used in various engineering fields because of their high-power density and high efficiency [6][7][8][9].…”