Multiple coupled circuit modelling approach for squirrel cage induction machine under single‐broken‐bar fault with stator winding functions decomposed in d – q rotor reference frame

Mathematical modelling is a fundamental issue in the condition monitoring and fault diagnosis of electrical machines. This study presents a multiple coupled circuit approach for the modelling of squirrel cage induction machines (SCIMs) with a single broken bar. Derived by means of winding function, the model is capable of incorporating all the harmonics of air‐gap magnetomotive force and describing transient machine behaviours. A d – q reference frame fixed on rotor is introduced. Each stator winding function is decomposed into two parts, a q ‐axis and a d ‐axis component, both of which induce currents in each rotor mesh. The q ‐axis and d ‐axis equivalent circuits are developed for both healthy and faulty cage rotors. It is also shown that a single‐broken‐bar fault does not affect the q ‐axis rotor mesh current distribution. The d ‐axis equivalent circuit for healthy cage rotor is modified further to determine the deviations in the mesh currents due to bar breakage. A detailed model of a 2.2 kW, four‐pole, three‐phase, 28‐rotor‐bar SCIM is implemented in MATLAB/Simulink environment, and a laboratory test bed is set up for this machine. A comparison between the simulation and experimental results verifies the effectiveness of the proposed modelling approach.