MAGNETIC CORES - TESTING AND INSPECTION

摘要

Several varieties of high frequency soft magnetic cores are used. Useful testing depends on the type of core and the intended application. This paper addresses the considerations a test engineer should apply in the testing of high frequency magnetic cores. Ferrite cores are tested for permeability, loss factor, Q, core losses, saturation, remanence, resistivity, DC Bias performance, and the temperature effects of each of these. Additional tests include mechanical and visual evaluations. The ferrite properties are interrelated, and an understanding of how temperature, drive level, bias, and frequency interact is necessary in order to construct useful tests. In addition, fixturing has an impact on the measurements obtained, and it is important to understand the effects of bobbin fill, leakage flux, and the specification of air gaps. Powder cores such as MPP, High Flux, and Kool Mμ toroids and E-cores are used in many applications similar to those of ferrite, yet the behavior of powder cores is different in significant ways. An understanding of the performance of powder cores at various drive levels, bias levels, frequencies and temperatures is necessary for proper testing. Kool Mμp. E-Cores introduce several new behaviors to consider.