NdFeB magnets for electric power steering (EPS) applications

Summary form only given. In terms of limiting cogging torque, the success of a NdFeB magnet in a motor application is dependent upon magnetic orientation (e.g. parallel or radial) and remanence (B/sub r/) uniformity across the part. Brushless direct current motors (BLDCMs) for electric power steering (EPS) applications are instances where minimal cogging torque is required. This paper quantifies the magnetic orientation and uniformity of various geometries of both sintered and hot-deformed fully-dense NdFeB magnets applicable to EPS motor assemblies: straight arcs, skewed arcs, and full rings. Cogging torque measurements, using a typical BLDCM design for EPS, allow for the correlation between motor cogging torque and the uniformity and orientation of the remanence (B/sub r/) of the magnets. It is shown that poor B/sub r/ uniformity induces high cogging torque in the motor.