Space harmonics analysis of the main air gap flux of an induction motor and its applicability to detect faults

Condition monitoring of an induction motor may be based on measuring the electrical signals, such as stator current, electromagnetic flux etc. or mechanical signals such as vibration, noise etc. from the motor. Most of the existing electrical techniques of condition monitoring and fault diagnostics are based on the stator current and/or leakage flux measurement outside the motor. Besides, most of these methods only concentrate on the time harmonics analysis of the acquired signal. But the main air gap flux consists of both time and space harmonics. The latter is overlooked by most of the existing researches. We propose to analyse the space harmonics of the main air gap electromagnetic flux along with the time domain analysis. But to do so, a thorough knowledge of the space harmonics of the stator flux, the rotor flux and their insights is needed to be obtained. To this aim, we present the space harmonics analysis of the main air gap flux of a healthy induction in this paper. Then the applicability of the space harmonics analysis to detect the faults is discussed. Two types of rotor faults, i.e. eccentricity and the broken rotor bar fault are discussed.