A new method of accurate broken rotor bar diagnosis based on modulation signal bispectrum analysis of motor current signals

Abstract

Motor current signature analysis (MCSA) has been an effective way of monitoring electrical machines for many years. However, inadequate accuracy in diagnosing incipient broken rotor bars (BRB) has motivated many studies into improving this method. In this paper a modulation signal bispectrum (MSB) analysis is applied to motor currents from different broken bar cases and a new MSB based sideband estimator (MSB-SE) and sideband amplitude estimator are introduced for obtaining the amplitude at s f s) 2 1 (  (s is the rotor slip and s f is the fundamental supply frequency) with high accuracy. As the MSB-SE has a good performance of noise suppression, the new estimator produces more accurate results in predicting the number of BRB, compared with conventional power spectrum analysis. Moreover, the paper has also developed an improved model for motor current signals under rotor fault conditions and an effective method to decouple the BRB current which interferes with that of speed oscillations associated with BRB. These provide theoretical supports for the new estimators and clarify the issues in using conventional bispectrum analysis.

The identification of shaft current induced defects on rolling bearings in wind turbine generators

“…According to the references [10][11][12][13][14][15], MSB is an effective demodulation technique and demonstrated to be able to detect bearing faults under heavy noise influences, Based on Fourier transform   Xf of a vibration signal x , MSB is defined as the following equation.…”

“…Gu et al named this method as the Modulation Signal Bispectrum (MSB) analysis and achieved fault diagnosis of downstream mechanical equipment using electrical motor current signals in 2011 [10]. After that, their team continues to deeply study and analyse the method to achieve a series of achievements [11][12][13][14][15].…”

Diagnosis of combination faults in a planetary gearbox using a modulation signal bispectrum based sideband estimator

“…It is a 6008ZZ deep groove ball bearing and its geometric dimensions that needed for fault frequency calculation are listed in Table I. (15) where the product between the upper sideband ) ( (15), the sideband products which associate with a constant phase value can be enhanced, while the noise and interfering components with random phases are suppressed effectively. This MSB based approach has been shown to yield outstanding performance in characterizing the small modulating components of motor current signals for diagnosing different electrical and mechanical faults under different load conditions [13][14] [15].…”

Detection and diagnosis of compound faults in induction motors using electric signals from variable speed drives

“…Sharifi and Ebrahimi [9] developed a method for the diagnosis of short circuit faults. More details on MCSA have been presented in [10] on the new improved BRB diagnosis based on MSB. Flux and vibration analysis for the detection of stator faults was presented [11].…”