This paper deals with a new AC electric motor magnetic circuit structure made of shifted non-segmented grain oriented steel laminations. The aim of the paper is to understand with a finite element approach the local distribution of the magnetic flux density inside shifted laminations as well as in the air-gaps between them. It is shown that the air-gap flux distribution is not trivial at all and very difficult to appreciate.

An experimental method to characterize the magnetic properties of Grain Oriented Electrical Steel in the rolling direction is proposed in this paper. It relies on the use of three 25 cm Epstein frames combined to generate three test-frames of different lengths. This enables the identification of the effective specific losses of the electrical steel when magnetization is applied along the rolling direction. As a consequence, it evidences the deviation of the loss figures obtained using the standardised Epstein test. The difference in losses is explained by the fact that the described method gives “only” the losses attached to the straight parts. The concept of the magnetic path length as defined by the standard is discussed.

The magnetic material quality of transformer cores influences their emitted acoustic noise. The latter is generated by vibrations resulting from the effects of the Maxwell's forces, located in the corners, and the magnetostriction inside the magnetic steel. In this paper, two annular structures allow differentiating these two phenomena and analyzing the vibration origins. Then, two different materials are compared, leading to conclusions about the influence of the material anisotropy on vibrations. At last, the measured vibration components are fully justified with the local saturation effects.

No abstract

Vibrations and noise in transformers core have two main origins: the Maxwell's forces, located in the corners, and the magnetostriction inside magnetic steel. In this paper, these two phenomena are differentiated and analyzed and analyzed using a test bench, which allows comparing the vibrations of two different annular structures. In the first case only the magnetostriction occurs, whereas the second case is submitted to both the magnetostriction and the Maxwell's forces.