Thermal Analysis of Low-Power Three-Phase Induction Motors Operating under Voltage Unbalance and Inter-Turn Short Circuit Faults

Amel Adouni,Antonio J Marques Cardoso

doi:10.3390/machines9010002

Abstract

Three-phase induction motors are considered to be the workhorse of industry. Therefore, induction motor faults are not only the cause of users’ frustrations but they also drive up the costs related to unexpected breakdowns, repair actions, and safety issues. One of the most critical faults in three-phase induction motors is related to the occurrence of inter-turn short circuits, due to its devastating consequences. The topic of inter-turn short-circuit faults in three-phase induction motors has been discussed over recent decades by several researchers. These studies have mainly dealt with early fault detection to avoid dramatic consequences. However, they fall short of addressing the potential burnout of the induction motor before the detection step. Furthermore, the cumulative action played by an inevitable degree of unbalanced supply voltages may exacerbate such consequences. For that reason, in deep detail, this paper delves into the thermal analysis of the induction motor when operating under these two harsh conditions: unbalanced supply voltages and the presence of the most incipient type of inter-turn short-circuit condition—a short-circuit between two turns only. In this work, the finite element method has been applied to create the faulty scenarios, and a commercial software (Flux2D) has been used in order to simulate the electromagnetic and thermal behavior of the machine for various degrees of severity of the aforementioned faulty modes. The obtained results confirm that the diagnostic tools reported in the literature might not be effective, failing to warrant the required lead time so that suitable actions can be taken to prevent permanent damage to the machine.

Highlights

The induction motor (IM) is widely used in industry because it provides good performance as well as high reliability and durability [1,2]
Experimental testbeds used to validate the fault diagnostic tools proposed in the literature impose controlled short-circuit conditions, resorting to a current limiting resistor, placed outside the stator frame of the machine
This paper focuses on the thermal behavior of an IM working under two harsh conditions: unbalanced supply voltages and the presence of the most incipient type of inter-turn short-circuit condition—a short-circuit between two turns only

Summary

Introduction

The induction motor (IM) is widely used in industry because it provides good performance as well as high reliability and durability [1,2]. IMs can be found in many applications which create, in turn, potentially stressed conditions. Working under these conditions adversely affects IMs performance [3]. IMs fault diagnosis is very important, as it avoids dramatic consequences to the machine itself and to the surrounding environment. The major faults that can affect the operation of electrical machines, are broadly classified as: (1) stator faults, resulting from the opening or shorting of one or more turns; (2) abnormal connection of the stator windings; (3) broken rotor bars or cracked rotor end-rings; (4) static and/or dynamic air-gap eccentricity; (5) bent shaft (akin to dynamic eccentricity) which can result in a rub between the rotor and stator, causing serious damage to the stator core and windings; (6).

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