Torque control during pole-changing transition of a 3:1 pole induction machine

Pole-phase modulation is a method of adjusting the pole- phase ratio of an electrical machine. Based on this method, an induction machine has been developed to operate in either a 12pole-3phase or a 4pole-9phase configuration. A novel control scheme was developed to control the motor during the pole-changing transition allowing continuous torque production. During the transition the motor is controlled as two independent motors, using the same stator windings and iron core. This field orientation control based scheme requires the realization of two sets of independent current commands on the motor´s nine stator windings. In addition, the two current sets have to be obtained from motor´s measured stator currents. This paper presents a current transformation between two independent orthogonal reference frames and a nine-axes reference frame.