Electromagnetic Properties of Soft Magnetic Composites and Electrical Steels at High Frequencies Considering Material Manufacturing Techniques

Abstract

A comprehensive magnetic comparison study is conducted on ring samples comprised of Soft Magnetic Composite (SMC) and electrical steel materials. The testing is performed under DC and AC conditions in an effort to characterize the materials magnetic compatibility for use in the increasingly prevalent research area that is high-speed electrical machines. DC tests show the improved magnetization characteristics for electrical steels emerging from their smooth, unimpeded microstructure. The measured DC characteristics and data obtained from simulation software can be vastly different. The magnitude of which is shown to be over 100 %. High-frequency AC loss measurements find that SMC and particularly thin electrical steel materials maintain a superior performance over thicker laminations at frequencies commonly encountered in high-speed machines. Hysteresis loop measurements highlight the extent of deterioration due to mechanical cutting of each material and a discussion on the possible underlying causes based on material properties is given. Cross-over frequencies of SMC grades over laminations are found to be as low as 68 Hz. AC loss results are compared with Finite Element Analysis (FEA) simulations and highlight the tendency for machine designers to employ a build factor when calculating iron loss during the design stages of a machine. A build factor is simply an error between simulated and measured loss. Errors are shown to be as high as 70 % for lamination materials and 2 % for SMC. FEA clearly does not account for the degradation of materials during cutting. This problem can be addressed with the proposal of new loss coefficients chosen according to the cutting technique and should also be a function of frequency and induction. This is a potential research area for future work.