Quantitative evaluation of induction motor broken bars by means of electrical signature analysis

Abstract

The paper reports the comparison and performance evaluation of different diagnostic procedures that use input electric signals to detect and quantify rotor breakage in induction machines supplied by the mains. Besides the traditional current signature analysis based on one-phase current spectrum lines at frequencies (1 2 ) , the procedures based on analysis of the line at frequency 2 in the spectrum respectively of electromagnetic torque, space vector current modulus, and instantaneous power are considered. These last procedures have similar features and the comparison is developed on the basis of instantaneous torque. It is addressed that the speed ripple introduces two further terms in the instantaneous torque, decreasing the accuracy of the diagnosis. It is shown that there is a link between the angular displacement of the current sideband components at frequencies (1 2 ) . This allows a more correct quantitative evaluation of the fault and shows the superiority of the sideband current components diagnostic procedure over the other proposed methods.

Modelling and simulation of stator and rotor fault conditions in induction machines for testing fault diagnostic techniques

“…Consequently, this will induce frequency harmonics in the stator current. The impact of broken rotor bars can be modelled by unbalancing the rotor resistance, the inductance changes are neglectable due to its insignificance influence compared to the resistance changes [16,20]. For simplicity, for a squirrel-cage rotor, the end-ring contribution is also neglected [16,17].…”

“…Any fault will induce a certain degree of asymmetry. Therefore, broken rotor bars and shorted stator windings are modelled by unbalancing the rotor and stator parameters in certain manners, accordingly [16][17][18].…”

“…The resistance changes is derived based on the assumption that the broken bars are contiguous, neither the end ring resistance nor the magnetizing current is taken into account, as following. The phase rotor equivalent resistance of a healthy induction motor is given as [16] …”

Condition Monitoring and Diagnosis of Faults in the Electric Induction Motor

“…In all the methods of detection of the failures suggested in the literature [11][12][13][14] , one must take one or more signals to treat them, analyze them and conclude, with certainty, if there is a failure or not.…”

Fault Diagnosis of Induction Motors Based on FFT

“…This method is based on the fact that an unbalanced machine when supplied with a three phase balanced voltage produces specific components in the stator current, whose magnitude and frequency depends on the asymmetry level and nature of the fault (Bellini et al, 2002). This method is based on the current signal spectrum decomposition, analyzed via the Fast Fourier Transform.…”