Design of three- and five-phase induction and permanent magnet synchronous prototype machines for systematic comparison

Inhalt:
A five-phase squirrel cage induction machine as well as a permanent magnet synchronous machine are designed for operation with 3rd harmonic injection to be compared with their three-phase counterparts. The prototype machines are based on a IE3 three-phase TEFC off-the-shelf standard induction motor with 15 kW nominal power at 1475 rpm and 400 V. For a proper comparison, also the three-phase rotor cage is redesigned, so the three- and five-phase induction motors and the three- and five-phase permanent magnet synchronous motors are especially designed at the same electrical, mechanical, geometrical and thermal constraints. The simulated five-phase induction machine performs only slightly better with a 0.02 % higher efficiency without and a 0.05 % higher efficiency with 3rd harmonic voltage injection. The simulated five-phase permanent magnet machine performs better by 0.1 % without and 0.13 % with a 3rd harmonic current injection for additional torque. Even if no 3rd harmonic current and torque are requested, the 3rd harmonic permanent magnet rotor field induces the five-phase stator winding, leading to a 3rd harmonic parasitic current, which needs to be eliminated by a 3rd harmonic stator voltage. The designed machines are not heavily saturated at nominal operation due to high efficiency requirements. Thus, they do not contain a significant 3rd harmonic saturation field.