Detection of broken bars in induction motor using voltage pattern analysis

The paper presents an application of a rotor broken bars detection method in induction motor drives with Field Oriented Control (FOC). Rotor fault distorts the magnetic symmetry and subsequently deteriorates the steady-state and dynamic performance. As fast speed control loop compensates for the unevenly distribution of the field, the inverter supply voltage is adjusted accordingly. The modulated supply voltage pattern is then analyzed and its average duty cycle is determined. When broken rotor bars are present, specific oscillations in the average duty cycle arise. The presence of these oscillations is sufficient for a successful detection. The computation is performed using simple mathematics and demands no significant computational power. The results confirm the suitability of the proposed detection method for FOC scheme.