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By John G. Webster (Editor)

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A. J. Moses Importance of rotational losses in rotating machines and transformers, J. Mat. Eng. Performance, 1 (2): 236–244, 1992. 12. Y. Alinejad-Beromi A. J. Moses T. Meydan New aspects of rotating field and flux measurement in electrical steel, J. Magn. Mag. , 112: 135–138, 1992. 13. A. J. Moses Effect of stresses on magnetic properties of siliconiron laminations. J. Mat. , 9: 217–222, 1974. 14. A. J. Moses P. S. Phillips Some effect of stress in Goss-oriented silicon iron, IEEE Trans. , 14: 353–355, 1978.

When used in a core the magnetization conditions are very complex. Nonuniform flux, flux harmonics, rotational and normal flux, flux deviation from the rolling direction of the sheet, and the influence of temperature and mechanical stress variations all cause additional losses. The deterioration of performance in a core is quantified in terms of the building or destruction factor which is defined simply as the ratio of the per unit core loss of a device to the nominal per unit loss measured under ideal test conditions at the same flux density.

Tational loss into hysteresis, eddy current, and anomalous loss components as is normally carried out for unidirectional ac magnetization but the total loss can be obtained from Pr = 1 T T hx 0 dbx dby + hy dt dt dt (9) where hx and hy are instantaneous tangential surface field components in orthogonal directions. dbx /dt and dby /dt are the rates of change of corresponding flux density components. Experimentally the components in Eq. (9) can be obtained using sensors (12). The rotational field variation needed to produce pure rotational flux density is complex in grain-oriented material as shown in Fig.

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