Comparative harmonic loss measurement in grain oriented and non-oriented magnetic sheets using a precision single-sheet tester

摘要

Although total flux is usually sinusoidal in magnetic cores, local flux may be distorted in some of their regions. While attempting to predict the loss distribution in materials operating under localized distorted flux conditions, which may occur in electromagnetic machines and transformer cores, it is very essential that proper account of the waveform be taken. Moreover for the development of new magnetic materials and the generation of better magnetic sheets, it is necessary to implement detailed measurement for their property specifications. One of these property specifications is the loss under distorted flux conditions. A high precision single-sheet tester (SST) was implemented in which the specification of the sample sheet will be measured by software processing of B and H. The finite-element method was used for the magnetic field study. The field distribution was calculated inside and outside the sample, through which the error was obtained. By a different section of the winding in exciting coil, the field uniformity was improved and finally the implemented system shows error less than 0.6% in the measurement of hysteresis loss of magnetic sheets. The loss due to distorted flux was measured for different harmonics and in distinct amplitudes and phases. A range of non-oriented and grain oriented materials was tested under distorted flux waveform conditions. For non-oriented sheets, the loss was measured about 10% by applying 15% third harmonic to exciting waveform, while this value was about 25% for many grain oriented sheets. Moreover, based on implemented measurements, the harmonic phase affects the loss and makes about 22% error in loss prediction for non-oriented sheets.