Study On Measurement Method Of High Frequency Rotating Magnetic Properties For Soft Magnetic Materials

The accurate simulation and measurement for high frequency rotating magnetic properties of soft magnetic materials is key factors in design and performance optimization of the electrical apparatus.Nanocrystalline and super-thin silicon steel materials are gradually replacing the traditional electrical steel and ferrite as the core of three-phase high power high-frequency transformer and high efficiency motor.However,the magnetic properties measurement method of nanocrystalline material is confined to the ring specimen method,which does not accurately reflect the direction difference of B and H and rotating magnetic field exist in multiphase power equipment widely.And the rotating magnetic properties measurement of super-thin silicon steel is still at the low frequency field around 1kHz.Therefore,it is necessary to study the measurement method of high frequency rotating magnetic properties for soft magnetic materials.The two dimensional high frequency rotating magnetic properties measurement methods of soft magnetic materials are studied,which focuses on the optimization of the magnetic circuit,the design of sensor,the design of excitation windings and the analysis of the high-frequency effect.The details are as follows:(1)The preparatory work for design of the two-dimensional rotating magnetic properties tester is completed.The alternating magnetic properties measurement of high oriented steel and super-thin silicon steel under different frequencies are performed by improved single sheet tester with double yoke.The alternating magnetic properties of nanocrystalline are measured by ring specimen method under different frequencies.(2)Several common magnetic circuit structures of two-dimensional rotating magnetic properties tester are compared and analyzed,and the core structure suitable for the rotating magnetic properties measurement with stacked sample are designed and made.The rationality of magnetic circuit design and the influence of core machining error on testing magnetic field is analyzed by finite element method.In addition,the optimization design of magnetic pole is carried out.(3)The composite magnetic sensor combined with probe and induction coil is designed,and the correction method of induction coil coefficient is proposed.The effect of distributed capacitance on the test accuracy of induction coil is analyzed by establishing the RLC equivalent circuit.In order to ensure the consistency of the sample position after changing the sample,a cube structure sensor box is designed.(4)A trapezoidal sectional structure excitation winding fitting for broadband magnetic properties measurement is designed.Analytic calculation method of distributed capacitance method with different winding mode is proposed,and comparing with the finite element calculation results.The distributed capacitance simplified finite element calculation method is proposed,meanwhile the automatic modeling and simulation program is designed to improve the efficiency of finite element simulation.The skin effect,proximity effect and the squeeze effect of winding are analyzed at high frequency.A current homogenization method is proposed for the non-uniform distribution of current in windings.According to the application characteristics of Litz and copper foil,the winding material is selected and the specific structural parameters are determined.