Speed & position estimation by demodulating rotor slot harmonics

It is well known that slotting harmonics exist in most of the electrical machines. These harmonics may supply valuable information for condition monitoring of bearings, windings or rotor bars. Utilization of these harmonics for rotor speed and position estimation is limited mainly due to long sampling periods required by spectral estimation techniques. In this study, a novel speed and position estimation method is proposed that does not need any kind of spectral estimation. In this approach extracting the required information can be done within a typical control cycle of a vector controlled drive algorithm. In the application of the method, higher order rotor slot harmonics have been utilized. The approach is explained in the paper and illustrated with experimental results.