Magnetic Performance Improvement Caused by Tensile Stress in Equivalent Iron Core Fabricated by High-Strength Non-Oriented Electrical Steel

This article presents the application of high-strength non-grain-oriented (NGO) silicon steel in the design of the rotor topology of a high-speed interior permanent magnet synchronous machine (IPMSM). By narrowing the magnetic bridges and center posts in the rotor, the purpose of reducing leakage flux and increasing output torque is achieved. Narrower magnetic bridge will cause electromagnetic loss concentration and tensile stress concentration, and tensile stress can effectively weaken the core loss at the part where the iron loss is concentrated. The high-strength NGO silicon steel used in this article is SW35YS600. This high-strength NGO adopts the method of increasing dislocations density to achieve the goal of increasing the structural strength while taking into account the electromagnetic properties at the same time. The electromagnetic properties of this high-strength NGO are less sensitive to tensile stress. As the frequency increases, the improvement of tensile stress on iron loss increases. However, after this material undergoes stress relief annealing, its electromagnetic and mechanical properties deteriorate significantly. Observing the grain structure, it was found that the grains of the high-strength NGO increased significantly after annealing.