Measurement of rotational power losses in silicon-Iron sheets using wattmeter method

Development of a rotational power loss measuring system based on the wattmeter method for a single Epstein strip and a brief discussion of magnetization processes of Si-Fe sheets under the rotational magnetizing condition are described. The pick-up coil system has a configuration with a flux search coil sandwiched by two magnetic field search coils, with which the components of the field parallel and transverse to the longitudinal direction of a specimen are separately detected. The flux search coil has two windings wound along diagonal lines of a square insulator into which the specimen is inserted. Addition and subtraction of two output voltages from these windings give the signals proportional to the flux change rate in the directions parallel and transverse to the longitudinal direction of the specimen. Therefore, two values of losses corresponding to two magnetizing directions are obtained using wattmeters. Summation of these loss values gives the rotational power loss. Since magnetizing processes in both directions are closely related each other through the domain wall movement and the rotation of magnetization in the specimen, losses are quite different from those obtained from an alternating magnetization in the higher magnetization range in which even a minus loss can be observed.