2/4 POLES split phase capacitor motor for small compressors: A comprehensive characterization

Compressor electric motor drives play a key role in energy consumption of residential refrigerators. Electrical efficiency, robustness to starting and overloads and speed variation range define the performance of compressor electric motor drives. Between the lowest cost fixed speed split phase capacitor grid-connected induction motor, with lower efficiency, and the higher-efficiency grid connected cage PM rotor split phase capacitor motor and the inverter fed variable PM synchronous motor of highest initial costs, we introduce in this paper a 2 speed grid-connected motor drive. The proposed topology uses a separate split phase winding, cage-PM-four-pole rotor synchronous motor (PMSM) for low speed (4 pole) and a single phase (main) winding for 2 pole operation. The target is 85% efficiency at 50W output for 4 poles (low speed) PMSM operation with good starting and at least 60% efficiency in 2 pole (high speed) induction motor operation at 100W, with smooth transients from low to high speed under full torque load. Circuit models for steady state and for transients with dedicated Matlab codes have been developed, with key FEM validation, to substantiate full scale experiments as the main contributions of the paper for a ready to use industrial solution.