Experimental Characterization and Feasibility Study on High Mechanical Strength Electrical Steels for High-Speed Motors Application

Sleeves are frequently used for protecting high-speed rotors from high centrifugal forces at high speeds. Currently, metal sleeves such as titanium and inconel alloys and fiber sleeves such as carbon fiber and glass fiber are commonly used. Metal sleeves have high eddy current losses due to armature reaction. Fiber sleeves can avoid high eddy current losses. However, heat dissipation abilities of the rotors are decreased. Moreover, fiber sleeves are sensitive to temperature and manufacturing processes. Hence, sleeve-free interior permanent-magnet rotor structure is attractive. To avoid sleeves, electrical steels of high mechanical strength and low core losses are required. Amorphous metal has been proved as a good candidate for such application. It can help to improve the power density and efficiency based on a study of a 15.7 kW, 125 000 r/min IPM demonstrator motor. However, because the mechanical strength of amorphous metal is easily degraded during core manufacturing, a high-silicon steel, 10JNEX900, is considered as an alternative. The electromagnetic and mechanical properties of 10JNEX900 are tested. A prototype made from amorphous metal 2605SA1 is tested to verify the simulation methods and it is used as a benchmark motor to study the feasibility of the new rotor core material.