Detection of broken rotor bars in induction motors using state and parameter estimation

The hypothesis upon which detection is based is that the apparent rotor resistance of an induction motor will increase when a rotor bar breaks. Here, the apparent rotor resistance is that in the balanced single-phase electrical model of an induction motor operating at constant velocity. To detect broken rotor bars, measurements of stator voltage, current, excitation frequency, and rotor velocity are taken over a small range of velocity. These measurements are processed by a near-least-square-error estimator to produce estimated motor states and parameters. In particular, rotor resistance is estimated and compared to its nominal value to detect broken rotor bars. The estimate is compensated for thermal variation. The broken-rotor-bar detector is evaluated experimentally using one stator and three rotors from identical 3 hp induction motors.<>