Comprehensive Review of Bearing Currents in Electrical Machines: Mechanisms, Impacts, and Mitigation Techniques

Tianyi Pei, Hengliang Zhang (), Wei Hua and Fengyu Zhang
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Tianyi Pei: School of Electrical Engineering and Automation, Fuzhou University, Fuzhou 350108, China
Hengliang Zhang: Engineering Research Center of Electrical Transport Technology, Ministry of Education, Southeast University, Nanjing 210096, China
Wei Hua: Engineering Research Center of Electrical Transport Technology, Ministry of Education, Southeast University, Nanjing 210096, China
Fengyu Zhang: Power Electronics Machines and Control (PEMC) Research Group, University of Nottingham, Nottingham NG7 2RD, UK

Energies, 2025, vol. 18, issue 3, 1-34

Abstract: The present paper deals with a review on bearing currents in electrical machines, with major emphasis on mechanisms, impacts, and mitigation strategies. High-frequency common-mode voltages from the inverter-driven system have been found to be the main reason for bearing current leading to motor bearing degradation and eventual failure. This paper deals with bearing currents—electrical discharge machining (EDM) currents, circulating bearing currents, and rotor-to-ground bearing currents—and the various methods of their generation and effects that are harmful to the bearings and lubricants of a motor. Mitigation techniques, among which the following have been taken into account, are studied in this context: the optimization of PWM modulation, and the use of shaft grounding brushes, insulated bearings, and passive or active filters. Finally, advantages, limitations, and implementation challenges are discussed. A review comparing three-phase and dual three-phase inverters showed that, due to the increased degree of freedom in modulation strategies, it is possible to eliminate common-mode voltages through active modulation techniques. Such added flexibility will reduce the risk of bearing currents effectively. It also highlights future research directions in bearing current suppression, including the development of multi-phase motor systems, real-time monitoring technologies with artificial intelligence, and the use of new insulation materials for the enhancement of bearing reliability. The results obtained should guide future research and engineering practices in suppressing bearing currents to improve motor durability with high performance.

Keywords: bearing current; shaft voltage; common-mode voltage; multi-phase motor systems; pulse width modulation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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