Importance of rotational losses in rotating machines and transformers

Abstract

There are increasing calls for a standard specification for the measurement of rotational losses in electrical steels and amorphous magnetic materials. However, the question still remains as to whether rotational losses are sufficiently important in practice to merit the implementation of a special standard. This paper explains what rotational magnetization is and how the losses occur. It then gives a brief explanation of the measurement difficulties encountered. Regions of transformers and rotating machine cores where rotational flux occur are illustrated and an estimate of the resulting rotational losses is made. It is shown that the proportion of rotational loss in transformers is not generally high, whereas in motors it can amount to more than 50% of the total core loss. The results indicate that rotational loss is of sufficient importance in motors to merit the establishment of standardized methods of measuring it in magnetic materials.