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The effects of varying the modulation index and the switching frequency on steel lamination core losses when excited with pulse width modulated waveforms are first investigated. A switched reluctance motor flux model is also developed and flux waveforms for different parts of the machine are synthesized. Using these flux waveforms, the paper presents the loss trend inside a switched reluctance machine, showing the core loss variation of the machine. The rotor was found to incur higher losses than any other part inside the switched reluctance motor. The paper further identifies the flux density harmonics that contribute to higher core losses in the rotor. Using the Fourier series, an attempt to predict core losses under switched reluctance motor flux density waveforms is done and the predicted results are compared with measurements. An Epstein frame was used for direct core loss measurements on 0.0140 in. [0.36 mm] commercial electrical steel; the methods and test bench used, along with test results are detailed in the paper.

In this paper the behavior of non-oriented laminations when excited with PWM waveforms is analyzed. The USA and the European experiences in core loss measurements with PWM waveforms are compared, highlighting the different experimental approaches and the different test benches. Parameters that characterize a PWM source (i.e. switching frequency, modulation index, modulating waveform type and switching topologies) are varied to ascertain their influence on lamination specific core losses. Although a direct numeral comparison of results was not possible, test results from the two institutions harmoniously show a consistent deterioration of lamination properties when excited with PWM supplies. The problem approach proposed by the two institutions show understanding of core loss measurement methods with non-sinusoidal excitations and can be considered a starting point for future work on a development of a standard procedure for magnetic material characterization with PWM supplies. Test benches with the respective experimental results are detailed in this paper. 0-7803-8987-5/05/$20.00 ©2005 IEEE.

This paper presents a new Epstein frame optimized for high frequencies and high flux densities. The design philosophy and test results at high power frequencies are presented. The frame achieves high frequency and high flux density performance because of reduced number of turns and reduced number of samples, while using standard 25-cm Epstein samples. Some of its technical advantages over the current Epstein frames and the single sheet testers are less samples' preparation time and better material representability, respectively. Four lamination types were tested: 0.0250-in (0.64 mm) M36 and cold rolled motor lamination, 0.0184-in (0.47 mm) M19, and 0.0140-in (0.36 mm) M45. The results obtained show good agreement with the core loss data provided by the steel manufacturers measured using the old frames at 200, 300, and 400 Hz. Results at 600 Hz and 1.0 kHz are also presented for the M45 and M19 samples along with the test bench used.Index Terms-Core losses, Epstein frame, high flux density, high frequency.

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