Analytical and Experimental Study of Squirrel Cage Induction Motors with rotor bars faults

Abstract

In this paper, we present an analytical approach in order to study in efficiency way the spectral contents of the stator line currents of three-phase squirrel cage induction motors with broken rotor bars. This study is based on analytical expressions for the stator and the cage rotor magneto motive forces (MMF) which are derived using the winding function approach. Also, a simple approach is used to study the influence of broken rotor bars on the rotor cage MMF in order to estimate the frequencies of the spectral components induced in the stator windings. This approach assumes that one broken bar means that one rotor loop is absent. Consequently, the new rotor cage MMF, with broken bar, can be obtained by subtracting rotor MMF induced by the absent loop from the healthy rotor MMF. In addition, and taking into account the time supply harmonics, general expressions independent from the number of pole pairs are established which give frequencies of all related spectral components. This approach and the theoretical predictions are verified tanks to appropriate experimental tests.