Research On Power Loss Properties Of Electrical Steel Sheet Based On Measurement Technology Of Two-Dimensional Magnetic Properties

The alternating and rotating magnetic field exist simultaneously in the stator core of the motor under actual operating conditions. The core loss caused by the rotating magnetic flux is greater than that caused by the alternating magnetic flux. Due to the lack of measurement data of the rotational loss characteristics of electrical steel sheets, the approximate formulas are usually used to estimate the rotational loss in the calculation of the core loss, which will bring certain computation error in the design and analysis of the electrical equipments, especially in the research and design of major equipments such as ultra-large capacity generators and transformers. In this paper, a test system for rotating magnetic properties of electrical steel sheet was used to measure hysteresis characteristics and loss characteristics of electrical steel sheet under different magnetizations. On the basis of this, the traditional rotating ellipse model and the orthogonal decomposition model were improved, the calculation accuracy among different loss models were compared and analyzed through experiments. The main contents are as follows:First of all, the magnetic flux density and magnetic intensity waveform in one magnetization period for a non-oriented electrical steel sheet were measured by using a two-dimensional magnetic property tester under the standard magnetization conditions such as alternating magnetizations and rotational magnetizations. The influence of different magnetization trajectories on hysteresis loop and specific loss in electrical steel sheets was analyzed, and the rotational loss database of electrical steel sheet was established under the standard conditions.Secondly, several typical computational models taking rotational loss into account were studied, and then their advantages and disadvantages were analyzed and compared. Based on the measured data, the calculation errors of the traditional rotating ellipse model and the orthogonal decomposition model were discussed. Then two improved loss models were proposed by introducing the error terms into it, furthermore the calculation method of the loss of electrical steel sheet under the non-standard magnetic flux density waveform was presented.Then, a non-standard rotating magnetic field was generated by the two-dimensional magnetic property tester to verify the accuracy of the proposed loss calculation model. Thespecific loss in the electrical steel sheet was measured and computed by employing traditional rotating ellipse model and the orthogonal decomposition model and the corresponding improved ones. By comparing the calculated values with the experimental ones the improved model was proved to be more accurate.Finally, the magnetic field test model of a ring core was designed and built, and the magnetic flux density waveform data on several typical positions was measured. By Fourier analysis, the decomposed waveform data were applied to the loss calculation using the traditional and improved rotating ellipse model and the orthogonal decomposition model, and the calculation results by using loss model above were compared and analyzed.