Contents I. Introduction
Rotational magnetic flux is commonly generated in the cores of ac rotating machines and T-joints of three phase transformers. Magnetic core loss under the rotational magnetic flux has been studied in two-dimensional (2-D) magnetic measurements [1]. In square single sheet measurements, rotational loss has rarely been examined at so high magnetic flux density as the operating condition of electric machines because of the difficulty in realizing both high magnetic flux density and wide area of uniform magnetic flux density with sinusoidal waveform control at the same time. We have developed a new 2-D magnetic measurement method and succeeded in satisfying both of these requirements by adopting an exciting system without an air gap between the yokes and the sample sheet. With this new measurement method, we were able to examine the rotational loss of soft magnetic materials at high magnetic densities and the rotational-direction-dependent losses. As for the rotational loss, there have been some arguments about the loss differences between the rotational directions of clockwise and anticlockwise. The argument point is that the loss differences depend on angular position of the sensing coil axes in the measurement [2] or physical reason in the behavior of the materials [3]. Since the loss difference between the two directions tends to increase largely with magnetic flux density, the loss measurement at higher flux density should be essential. Here, we explain the new 2-D measurement and discuss the rotational losses of electrical sheets from the viewpoints of the rotational directions and the inclination angle of magnetic field () and magnetic flux density () sensing coil axes. Two-dimensional measurement setup. (a) Structure of yokes with slits and exciting coil frames. (b) Top view of and sensing devices. Block diagram of measuring system for 2-D magnetic measurement.
