Higher Order Rotor Slot Harmonics for Rotor Speed & Position Estimation

Air-gap flux of all electrical machines contains harmonics. Some of these harmonics stem from rotor slotting of the machine. These harmonics can be utilized for control or diagnostic purposes. In the literature, rotor slot harmonics are mostly utilized for condition monitoring. There is also some research utilizing them for rotor speed estimation. However, it is observed that in the existing work spectral analysis techniques are employed which require long samples of data and in this from they are not suitable for vector control of induction motors. Accurate position information is vital for high performance vector control of induction motors. Furthermore using a sensor which requires some kind of modification on the motor is not desirable. A novel method has been proposed in this study that does not need any spectral estimation techniques. In this approach extracting the required information can be done within a typical control cycle of a vector controlled drive algorithm. Furthermore, any modification of the motor is not necessary. In this paper the proposed approach is presented. Experimental results illustrate that the position prediction accuracy of the approach is very high.