The method of current measurement in the rotor cage bars of prototype induction motor with the use of Rogowski coils

The article presents a method of currents measurement in the rotor bars of a prototype induction motor with the use of Rogowski coils. Measuring coils are placed on each of the 30 cage bars of the rotor. Signals proportional to the derivative of rotor bars currents are led outside the machine to special slip rings and then from the band of brushes adjacent to the slip rings transmitted to the integrating amplifiers and recorded with help of measuring card and dedicated software. Studies were carried out during the machine normal operation state at different loads. The currents of squirrel cage bars, recorded for different cage damages, were processed and analyzed. The results of current measurements of cage bars with help of Rogowski coils were checked numerically. The possibility of using the measurements results to improve diagnostic algorithms for detecting induction motor cage damage have been presented.