Experimental and finite-element analysis of an electronic pole-change drive

The theory and modeling of an electronic pole-change drive for the purpose of extending the constant power speed range of a four-pole induction machine have been previously reported. This paper presents verification of the power capability characteristics of the proposed drive through experimental implementation. An indirect field-oriented controller is developed for the pole-change drive with the estimated rotor open-circuit time constant and d-axis-current commands dependent on the mode of operation. It is demonstrated that, for a constant power load, the drive can operate at 6340 r/min in two-pole mode without exceeding either the voltage or current limits at 3600 r/min in four-pole mode. A finite-element method is also utilized to examine the influence of magnetic saturation on the pole-change drive performance. The nature of the magnetic flux distribution and saturation progression is investigated in both four-pole and two-pole modes. The saturation-induced inductance variation is also studied and its influence on the dq inductance matrix is quantified.