Yoshiya Higuchi

Integral equation method with surface impedance model for 3D eddy current analysis in transformers

To estimate the stray loss distribution in power transmission systems like transformers, a new 3D eddy current analysis technique has been developed. This technique is based on the Integral Equation Method with Surface Impedance Model and is suitable for calculating eddy currents in a magnetized substance that has a complicated structure like transformers do. This technique was applied to an actual transformer and a new shield concept was proposed.

A new vector element in the volume integral equation method for nonlinear magnetostatics

To calculate nonlinear magnetostatics a new vector element in the volume integral equation has been developed. The magnetization vector in an element is expressed by using co- and contra-variant vectors corresponding to the each surface of the hexahedron element. To accelerate the conversion process, the iteration procedure has been divided into initialization and convergence parts. The method has been applied to TEAM workshop problem 13 of IEEE. Its calculated results agree with the measured data within 2%, indicating the method provides good accuracy. >

Three dimensional eddy current calculation with integral equation method for transformers

To calculate eddy current on multiply connected magnetic substances, the frequency domain volumetric integral method has been developed. This method requires no air space grid; therefore, it is suitable for complicatedly structured objects such as transformers. Verification tests using simple plates show good agreements with analytical solutions. Two application tests to transformers are presented. In the 1st test which examines the magnetic flux density in the clamping plate, the calculated results agree with the measured ones within 10 to 30%. In the 2nd test which compares the calculated eddy current density with the measured temperature rise on the clamping plate, their results agree for the distribution property. Te suitability of this method for eddy current evaluation in power transmission equipment is confirmed.