A Reconfigurable Motor for Experimental Emulation of Stator Winding Interturn and Broken Bar Faults in Polyphase Induction Machines

The benefits and drawbacks of a 5-hp reconfigurable induction motor, which was designed for experimental emulation of stator winding interturn and broken rotor bar faults, are presented in this paper. It was perceived that this motor had the potential of quick and easy reconfiguration to produce the desired stator and rotor faults in a variety of different fault combinations. Hence, this motor was anticipated to make a useful test bed for evaluation of the efficacy of existing and new motor fault diagnostics techniques and not the study of insulation failure mechanisms. Accordingly, it was anticipated that this reconfigurable motor would eliminate the need to permanently destroy machine components such as stator windings or rotor bars when acquiring data from a faulty machine for fault diagnostic purposes. Experimental results under healthy and various faulty conditions are presented in this paper, including issues associated with rotor bar-end ring contact resistances that showed the drawbacks of this motor in so far as emulation of rotor bar breakages. However, emulation of stator-turn fault scenarios was successfully accomplished.

I. Introduction

Polyphase induction motors have been the workhorse (main prime movers) for industrial and manufacturing processes as well as some propulsion applications. They are commonly used in ac adjustable speed drives where torque and speed control is indispensable. The ruggedness, ease of control, and cost-effective design of squirrel-cage induction motors are the main appealing features to consumers and engineers for the various aforementioned applications. Due to its popularity, there have been many investigations on condition monitoring and fault diagnostics in electric machines throughout the literature, especially squirrel-cage induction motors [1]–[14]. This is because failure of such motors as prime movers can lead to significant undesirable repercussions such as production downtime, financial loss, adverse environmental effects, and possible personnel injury. Consequently, considerable interest in machine fault diagnostics received from industry and academia has prompted researchers to develop excellent state-of-the-art diagnostic techniques for various possible types of faults such as indicated in Fig. 1. The probability of occurrence of such faults is given in Table I (see [15] and [16]). Therein, both the stator and rotor faults account for around 40% of all faults. Accordingly, the main thrust of this paper centers on electrical stator and rotor faults. Fig. 1.

Induction motor fault categories.

Table I Percentage of Failures by Major Motor Components

Major Components	IEEE-IAS [15] % of Failures	EPRI [16] % of Failures
Bearing Related	44	41
Winding Related	26	36
Rotor Related	8	9
Other	22	14