Detection of broken bars and rings in induction machines

Determining the number of broken bars due to the failure or the number of ring segments of the rotor cage of induction motor is an important problem during the operation of such machine. The Unscented Kalman Filter (UKF), used to achieve this goal, provides precise information on numbers of broken bars and ring segments. To generate such information, the filter requires measurements of the stator currents and currents of additional single-winding coils located at the stator teeth and loaded with large resistances (~1 kΩ). The measurement of the rotational speed of the rotor and the related angle of the machine shaft rotation is also needed. The method of determining the numbers of broken bars and ring segments of the rotor and the method of detecting only the broken bars of the rotor cage were tested. The presented method can be used for the protection of large and expensive induction drives.