Industrial Practices in Repair, Maintenance, and Performance Evaluation of three-Phase Induction Motors: A Practical Case Study
Article Sidebar
Main Article Content
Repair and rewinding of three-phase induction motors is a routine but technically demanding activity in industrial maintenance workshops, and the quality of that work has a direct bearing on motor efficiency, reliability, and service life. While international standards (e.g., IEEE 43, IEC 60034 series, NEMA MG-1, ISO 21940-11) define acceptance criteria for insulation resistance, surge/impulse withstand, and rotor balancing, published literature rarely documents how these criteria are applied together on a single motor as it moves through a workshop repair cycle. This paper addresses that gap through a practical case study of a burnt-out three-phase induction motor processed at an industrial motor-servicing facility.
The objective of the study is to document, in a structured and reproducible format, the diagnostic and corrective sequence applied to the motor — direct current resistance (DCR) testing, insulation resistance (Megger) testing, surge testing, rotor static and dynamic balancing, mechanical reconditioning, and stator rewinding — and to compare the pre-repair (faulty) and post-repair (healthy) results against recognised acceptance limits. The motor was diagnosed with a grounded, turn-to-turn shorted stator winding (Megger reading of 0 MΩ and a shorted phase pair) and unbalance readings far above the workshop's 9 g acceptance threshold. Following stripping, rewinding with Class F insulation and vacuum-pressure impregnation (VPI), and two-plane dynamic balancing, the motor achieved an insulation resistance of 998–1000 MΩ, a maximum inter-phase DCR deviation of 0.2 Ω, superimposed surge waveforms across all three phases, and a final rotor unbalance below 9 g on both correction planes.
The novelty of this work lies in presenting a single, fully-instrumented before/after case record that links electrical diagnostics, mechanical balancing, and winding-design considerations (coil pitch, connection type) within one workshop cycle, and in framing the acceptance criteria used against established international standards rather than workshop convention alone. The findings are intended to serve as a practical reference for motor-repair technicians, junior engineers, and students, and as a template for reporting repair-quality data in a form suitable for later statistical or predictive-maintenance analysis.
Downloads
References
Abdulkareem, A., Anyim, T., Popoola, O., Abubakar, J., & Ayoade, A. (2025). Prediction of induction motor faults using machine learning. Heliyon, 11(1), e41493.
APEC-CAST. (2011). Survey of motor repair and rewinding practices and the impact on energy efficiency. Asia-Pacific Economic Cooperation (APEC), 1–45.
Electric Motor Faults. (n.d.). Power system protection: Electric motor faults and protection [Technical training material], 1–12.
Florkowski, M., Florkowska, B., & Zydron, P. (2012). Partial discharge measurements in rotating machines — Standards and applications. IEEE Electrical Insulation Magazine, 28(4), 14–21.
IEC 60034-15. Rotating electrical machines — Part 15: Impulse voltage withstand levels of form-wound stator coils for rotating a.c. machines. International Electrotechnical Commission.
IEEE Std 43-2013. IEEE recommended practice for testing insulation resistance of electric machinery. Institute of Electrical and Electronics Engineers.
IEEE Std 522-2004. IEEE guide for testing turn insulation of form-wound stator coils for alternating-current electric machines. Institute of Electrical and Electronics Engineers.
ISO 21940-11:2016. Mechanical vibration — Rotor balancing — Part 11: Procedures and tolerances for rotors with rigid behaviour. International Organization for Standardization.
Montanari, G. C., & Simoni, L. (1993). Aging phenomenology and modeling. IEEE Transactions on Electrical Insulation, 28(5), 755–776.
Nandi, S., Toliyat, H. A., & Li, X. (2005). Condition monitoring and fault diagnosis of electrical machines — A review. IEEE Transactions on Energy Conversion, 20(4), 719–729.
NEMA MG-1. Motors and generators. National Electrical Manufacturers Association.
Stone, G. C. (2005). Partial discharge diagnostics and electrical equipment insulation condition assessment. IEEE Transactions on Dielectrics and Electrical Insulation, 12(5), 891–904.
Waide, P., & Brunner, C. U. (2011). Energy-efficiency policy opportunities for electric motor-driven systems. International Energy Agency (IEA) Working Paper, 1–125.
Zhou, D., Li, H., Yang, Y., & Xu, W. (2019). A review of stator insulation state-of-health monitoring methods for electric machines. IEEE Transactions on Dielectrics and Electrical Insulation, 26(4), 1047–1063.
This work is licensed under a Creative Commons Attribution 4.0 International License.
All articles published in our journal are licensed under CC-BY 4.0, which permits authors to retain copyright of their work. This license allows for unrestricted use, sharing, and reproduction of the articles, provided that proper credit is given to the original authors and the source.