2D finite element analysis and force calculations for induction motors with broken bars

In this paper an ABC transient model of the three phase induction motor is developed that depends on self- and mutual inductance calculations based on accurate finite element analysis (FEA). This model can represent both healthy and broken bars’ conditions. The effects of that type of fault on the stator current, rotor bar currents distribution, the forces exerted on the rotor bars, the motor speed and motor torque are studied. It was observed that broken bar faults will cause fluctuations in the stator peak current and in the motor speed and torque. It was found that the asymmetry in the rotor bar currents will lead to asymmetrical distribution of the radial and tangential forces affecting the bars. The asymmetry in the tangential forces causes the fluctuations in the motor torque, while the asymmetry in the radial forces will increase the mechanical stresses on the rotor shaft.