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Reliable Detection of Induction Motor Rotor Faults Under the Rotor Axial Air Duct Influence
Yang, Chanseung,Kang, Tae-June,Hyun, Doosoo,Lee, Sang Bin,Antonino-Daviu, Jose A.,Pons-Llinares, Joan IEEE 2014 IEEE transactions on industry applications Vol.50 No.4
<P>Axial cooling air ducts in the rotor of large induction motors are known to produce magnetic asymmetry and can cause steady-state current or vibration spectrum analysis based fault detection techniques to fail. If the number of <B><I>axial air ducts</I></B> and that of <B><I>poles</I></B> are identical, frequency components that overlap with that of rotor faults can be produced for healthy motors. False positive rotor fault indication due to axial ducts is a common problem in the field that results in unnecessary maintenance cost. However, there is currently no known test method available for distinguishing rotor faults and false indications due to axial ducts other than offline rotor inspection or testing. Considering that there is no magnetic asymmetry under high slip conditions due to limited flux penetration into the rotor yoke, the detection of broken bars under the start-up transient is investigated in this paper. A wavelet-based detection method is proposed and verified on custom-built lab motors and 6.6-kV motors misdiagnosed with broken bars via steady-state spectrum analysis. It is shown that the proposed method provides the reliable detection of broken bars under the start-up transient independent of axial duct influence.</P>
Chanseung Yang,Tae-June Kang,Sang Bin Lee,Ji-Yoon Yoo,Bellini, Alberto,Zarri, Luca,Filippetti, Fiorenzo Institute of Electrical and Electronics Engineers 2015 IEEE transactions on industrial electronics Vol. No.
<P>Motor current signature analysis (MCSA) based on the 50/60-Hz sidebands has become a common test in industry for monitoring the condition of the induction motor rotor cage. However, many cases of unnecessary motor inspection or outage due to false alarms produced by rotor axial duct interference have been reported. If the number of axial ducts and poles is identical, this can produce 50/60-Hz sideband frequency components in MCSA that overlap with that of rotor faults, resulting in false alarms. However, there currently is no practical test method available for distinguishing rotor faults and false indications other than testing the rotor offline or under the startup transient. In this paper, the feasibility of using the rotor fault frequency component produced by the space harmonic waves is evaluated as a solution for the first time. Since the fifth or seventh space harmonics have a spatial distribution of flux that does not penetrate in the rotor yoke to reach the axial ducts, they do not produce false alarms. The proposed method is verified on 6.6-kV motors misdiagnosed with broken bars via the 50/60-Hz sidebands of MCSA. It is shown that it provides reliable online indication of rotor faults independent of axial duct influence and can be used for screening out false alarms.</P>
Sang Bin Lee,Doosoo Hyun,Tae-june Kang,Chanseung Yang,Sungsik Shin,Heonyoung Kim,Sungbong Park,Tae-Sik Kong,Hee-Dong Kim IEEE 2016 IEEE transactions on industry applications Vol.52 No.1
<P>Motor current signature analysis (MCSA) has become an essential part of the preventive maintenance program for monitoring the condition of the rotor cage in medium-voltage induction motors in the pulp and paper industry. However, many cases of false indications due to interference from the motor or the load have been reported. False indications can result in unnecessary inspection and outage costs (false positives) or major repair/replacement costs and loss of production (false negatives). The objective of this paper is to present the potential root causes of false indications and provide guidelines on how commercially available offline and online tests can be applied for identifying false indications from a field engineers' perspective. Case studies of false MCSA indications and results of alternative commercial tests for improving the reliability of the diagnosis are provided through measurements on 6.6-kV and laboratory motor samples. Finally, new test methods under research and development for reliable rotor fault detection are summarized, and unresolved problems are listed. This paper is expected to help field maintenance engineers prevent unnecessary motor inspection and forced outages and guide researchers target future research toward industrial needs.</P>