Measurement of Core Losses in Electrical Steel in the Saturation Region under DC Bias Conditions

This paper presents a method to measure and determine core losses in electrical steel for high flux densities under dc bias conditions for electric machine applications. Test conditions require ac flux on top of dc flux, which can saturate the system. It is desirable to have a test system that would generate high flux densities without increasing the size of the ac power supply. We propose an innovative core tester that can handle the power requirements of the magnetic circuit formed by the test specimen. The dc and ac operating requirements of the magnetic circuits are separated and individual components are combined in such a way that a dc bias is provided from the slowly varying high-power component and the ac field is supplied by the low-power high-bandwidth component. The proposed topology consists of ac and dc blocker filters that provide separate pathways for the ac and dc currents. Circuit simulations and experimental test results are presented to verify the effectiveness of the proposed system.