A New Approach for Broken Rotor Bar Detection in Induction Motors Using Frequency Extraction in Stray Flux Signals

Abstract

This work offers a reliable solution to the detection of broken rotor bars in induction machines with a novel methodology, which is based on the fact that the fault related harmonics will have oscillating amplitudes due to the speed ripple effect. The method consists of two main steps: Initially, a timefrequency transformation is used and the focus is given on the steady-state regime; thereupon, the fault related frequencies are handled as periodical signals over time and the classical Fast Fourier Transform is used for the evaluation of their own spectral content. This leads to the discrimination of sub-components related to the fault and evaluation of their amplitudes. The versatility of the proposed method relies on the fact that it reveals the aforementioned signatures to detect the fault, regardless of the spatial location of the broken rotor bars. Extensive finite element simulations on a 1.1MW induction motor and experimental testing on a 1.1kW induction motor lead to the conclusion that, the method can be generalized on any type of induction motor independently from the size, power, number of poles and rotor slot numbers.

Stray Flux Sensor Core Impact on the Condition Monitoring of Electrical Machines

“…The induced voltage in the sensor was recorded in an oscilloscope (7). As explained before, the pole connections were accessible in the shaft (8). In the connections, different resistances R F were connected to emulate inter-turn faults.…”

“…In the case of induction machines, many different cases, such as broken rotor bars [2], inter-turn faults [3], problems in the bearings [4] and even the insulation's health and ageing can be detected [5]. For these purposes, several techniques have been applied to analyze the stray flux, such as the bispectrum and covariance [6], the correlation coefficients [7] and the frequency extraction [8]. In some cases, two or more flux sensors are used [3,7,8].…”

“…For these purposes, several techniques have been applied to analyze the stray flux, such as the bispectrum and covariance [6], the correlation coefficients [7] and the frequency extraction [8]. In some cases, two or more flux sensors are used [3,7,8]. The mechanical speed frequency also has an important role in rotor electrical and eccentricity fault detection [9].…”

“…Throughout the literature, the most frequently used flux sensors to measure the stray flux in electrical machines are coreless coils, normally known as research coils [1,2,[4][5][6][7][8][9]. Some authors use rectangular-shaped coils [14,15].…”

Automatic Early Broken-Rotor-Bar Detection and Classification Using Otsu Segmentation

“…Although, many of the above-mentioned techniques provide high efficiency for BRB detection and classification, the major drawback in most of them is their high computational complexity. Hence, new methodologies based on traditional techniques such as the STFT are still being used [20,21]. For instance, a methodology based on FFT is presented in [20] to detect BRB conditions.…”