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, has 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 RPM in two-pole mode without exceeding either the voltage or current limits at 3600 RPM 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.