Abstract
Motor current signature analysis (MCSA) is a fault diagnosis method for induction machines (IMs) that has attracted wide industrial interest in recent years. It is based on the detection of the characteristic fault signatures that arise in the current spectrum of a faulty induction machine. Unfortunately, the MCSA method in its basic formulation can only be applied in steady state functioning. Nevertheless, every day increases the importance of inductions machines in applications such as wind generation, electric vehicles, or automated processes in which the machine works most of time under transient conditions. For these cases, new diagnostic methodologies have been proposed, based on the use of advanced time-frequency transforms—as, for example, the continuous wavelet transform, the Wigner Ville distribution, or the analytic function based on the Hilbert transform—which enables to track the fault components evolution along time. All these transforms have high computational costs and, furthermore, generate as results complex spectrograms, which require to be interpreted for qualified technical staff. This paper introduces a new methodology for the diagnosis of faults of IM working in transient conditions, which, unlike the methods developed up to today, analyzes the current signal in the slip-instantaneous frequency plane (s-IF), instead of the time-frequency (t-f) plane. It is shown that, in the s-IF plane, the fault components follow patterns that that are simple and unique for each type of fault, and thus does not depend on the way in which load and speed vary during the transient functioning; this characteristic makes the diagnostic task easier and more reliable. This work introduces a general scheme for the IMs diagnostic under transient conditions, through the analysis of the stator current in the s-IF plane. Another contribution of this paper is the introduction of the specific s-IF patterns associated with three different types of faults (rotor asymmetry fault, mixed eccentricity fault, and single-point bearing defects) that are theoretically justified and experimentally tested. As the calculation of the IF of the fault component is a key issue of the proposed diagnostic method, this paper also includes a comparative analysis of three different mathematical tools for calculating the IF, which are compared not only theoretically but also experimentally, comparing their performance when are applied to the tested diagnostic signals.
Highlights
Induction machines drive modern industry, and their failures, very rare due to their robustness, may produce high economic losses because of the sudden breakdown of production lines.The continuous monitoring of their condition may help reduce this risk, by allowing an early detectionSensors 2020, 20, 3398; doi:10.3390/s20123398 www.mdpi.com/journal/sensorsSensors 2020, 20, 3398 of incipient machine faults
This parameter compares the slope of the straight line obtained from a linear regression fit of the experimental frequency-slip points, and the slope of the theoretical instantaneous frequency (IF) pattern associated with the fault component: R IF = 1 −
A set of simple signatures for the characterization of fault harmonics associated with different kinds of faults in induction machines working in transient regime has been presented
Summary
Induction machines drive modern industry, and their failures, very rare due to their robustness, may produce high economic losses because of the sudden breakdown of production lines. Direct evaluation of the amplitude and trajectory of fault harmonics in a 2D time-frequency plane is a challenging task, even for experienced maintenance personnel, much more difficult than assessing their amplitudes at specific frequencies as in steady state This work addresses both problems, and proposes a new methodology for the diagnosis of three types of usual faults in induction machines, which is based on tracking the IF of the fault related components of the stator current during the functioning of IMs in transient regime. The evaluation of the ridges in linear time-frequency transforms (CWT with the Morlet Wavelet) These three methods will be presented briefly both theoretically and practically, using one of the principal fault harmonics of a simulated induction machine with a broken bar. The procedure for presenting the three selected methods consists of applying each method to obtain the IF of the LSHst of Figure 2 (bottom) in the slip–frequency plane, and comparing it with the theoretical IF given by Equation (1)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call