Stator and Rotor Faults Diagnosis of Squirrel Cage Motor Based on Fundamental Component Extraction Method

Guoqing An,Hongru Li

doi:10.1155/2017/1576381

Abstract

Nowadays, stator current analysis used for detecting the incipient fault in squirrel cage motor has received much attention. However, in the case of interturn short circuit in stator, the traditional symmetrical component method has lost the precondition due to the harmonics and noise; the negative sequence component (NSC) is hard to be obtained accurately. For broken rotor bars, the new added fault feature blanked by fundamental component is also difficult to be discriminated in the current spectrum. To solve the above problems, a fundamental component extraction (FCE) method is proposed in this paper. On one hand, via the antisynchronous speed coordinate (ASC) transformation, NSC of extracted signals is transformed into the DC value. The amplitude of synthetic vector of NSC is used to evaluate the severity of stator fault. On the other hand, the extracted fundamental component can be filtered out to make the rotor fault feature emerge from the stator current spectrum. Experiment results indicate that this method is feasible and effective in both interturn short circuit and broken rotor bars fault diagnosis. Furthermore, only stator currents and voltage frequency are needed to be recorded, and this method is easy to implement.

Highlights

Nowadays, squirrel cage motor has been widely used in the industrial and agricultural production because of its simple and rugged construction [1]
In the case of broken rotor bars, the extracted fundamental component can be filtered out accurately according to the results of fundamental component extraction (FCE) method, and the rotor fault components may emerge from the stator current spectrum
In order to show the effectiveness of FCE method in the interturn short circuit fault diagnosis, the calculations obtained by the traditional symmetrical component (TSC) method are shown in Table 2 [22]

Summary

Introduction

Squirrel cage motor has been widely used in the industrial and agricultural production because of its simple and rugged construction [1]. Reference [9] took stator negative sequence impedance as interturn short circuit fault characteristic; this method has robustness in the case of unbalanced power supply, because negative sequence impedance is the ratios of negative sequence voltage and current. Reference [18] utilized Hilbert transform to detect the broken rotor bar fault location through envelope analysis of start-up current, but it is very hard to achieve the on-line fault diagnosis. In the case of broken rotor bars, the extracted fundamental component can be filtered out accurately according to the results of FCE method, and the rotor fault components may emerge from the stator current spectrum. The paper is organized as follows: Section 2 presents FCE method, and the implementation of this method is introduced in both cases of interturn short circuit and broken rotor bars fault diagnosis.

Algorithm of FCE

Fault Diagnosis System for Squirrel Cage Motor

Experimental Results

Conclusions