Influence of Start Rotor Position on Three-Phase Short-Circuit Current in Dual Three-Phase Surface-Mounted PM Machines

This article investigates the influence of start rotor position on three-phase short-circuit (3PSC) current in dual three-phase surface-mounted permanent magnet (DTPSPM) machines. For DTPSPM machines with symmetrical winding configurations, the 3PSC analytical model considering PM flux linkage harmonics is developed. It shows that the variations of 3PSC peak current with start rotor position mainly repeat every multiple of π/3 in an electrical period due to the fifth and seventh harmonics. The start rotor positions causing the largest 3PSC peak currents heavily depend on the harmonic magnitudes and phases. Then, the 3PSC analytical model for DTPSPM machines with asymmetric mutual inductances in one winding group is developed. It shows that the variations of 3PSC peak current with start rotor position mainly repeat every multiple of π. For winding configurations with smaller M a c , M bc , and M ab , start rotor positions causing the largest d -axis peak current are about π/6+ k π, π/2+ k π, and 5π/6+ k π ( k = 1, 2, 3...), respectively. To obtain the largest q -axis peak current, such start rotor positions are about 7π/24+ k π, 5π/8+ k π, and 23π/24+ k π ( k = 1, 2, 3...). In addition, the influence of rotor speed and asymmetric level is discussed. Finally, finite-element simulation is performed and experiments are conducted to validate the theoretical analysis.