LOSS MEASUREMENTS ON AMORPHOUS-ALLOYS UNDER SINUSOIDAL AND DISTORTED INDUCTION WAVE-FORM USING A DIGITAL FEEDBACK TECHNIQUE

A newly developed digital feedback wattmeter, allowing power loss measurements in soft laminations under generic induction waveform is presented. The system is intrinsically free of auto-oscillations, typical drawback of analog feedback circuits, and can therefore be operated in a wide frequency range (0.5 Hz-100 kHz). Loss measurements performed by this setup under sinusoidal and distorted induction waveforms on Co based amorphous ribbons are reported. It is shown that the classical approximation to the prediction of power losses under distorted induction largely fails to account for the experimental results. A novel theoretical approach, based on the statistical theory of losses, is discussed and successfully applied to the experiments. In particular, it is shown that knowledge of the loss components under sinusoidal induction at a given magnetizing frequency permits one to make an accurate prediction of the effect of distortion at that frequency as well as other ones. Illustrative applications at 1 kHz and 100 kHz are reported.