Lamination core losses in motors with nonsinusoidal excitation with particular reference to PWM and SRM excitation waveforms

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

New Epstein Frame for Lamination Core Loss Measurements Under High Frequencies and High Flux Densities

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

Iron loss calculation considering temperature influence in non-oriented steel laminations

In this study, the temperature influence on iron loss of non-oriented steel laminations is investigated. The iron loss variation under different flux densities, frequencies and temperatures is systematically measured and analysed by testing two typical non-oriented steel laminations, V300-35 A and V470-50 A. The iron loss variation with temperature is almost linear in the typical operating temperature range of electrical machines. Furthermore, the varying rate of iron loss with temperature varies with flux density and frequency. A coefficient which can fully consider the temperature influence is introduced to the existing iron loss model to improve the iron loss prediction accuracy. The predicted and measured results show that the temperature influence on the iron loss can be effectively considered by utilising the improved model, i.e. the prediction accuracy of the improved iron loss model remains constant, even when the temperature varies significantly. A potential simplification of this improved model is also discussed in this study