Expansion of Motor High-Efficiency Area by Inserting Magnetic Composite Material into Rotor

Variable magnetic flux motors have been proposed to achieve high-efficiency operation over a wide drive range ranging from high torque to high-speed. This paper clarifies the high efficiency area expansion effect of a variable flux motor with a magnetic composite material inserted in the rotor. To achieve the effect of enlarging the maximum efficiency range, this motor uses magnetic composite materials with much lower saturation magnetic flux density and iron loss than electromagnetic steel plate. This paper reports the magnetic and mechanical properties of the magnetic composite material using Fe–Si–Al alloy, considering low iron loss. The simulation results clarified the variable magnetic flux characteristics for reducing loss at high-speed rotation by actively utilizing the magnetic saturation region of the magnetic composite material. The efficiency improvement in the high-speed region is attributed to the suppression of spatial harmonics without significantly reducing the q-axis inductance. Furthermore, the proposed motor achieves both the expansion of the high-efficiency range and relaxation of mechanical stress by increasing the thickness of the bridge part adjacent to the permanent magnet.