The Negative Value of Power in Rotational Core Loss Measurements

The increasing interest in magnetic measurements in machine laminations under rotating fields requires better interpretations for many unclear observations, which have been noticed and documented experimentally. One of these observations is the negative value of power, which is reported during the measurements of rotational core losses using the field metric method. This paper addresses the problem of negative power and gives a descriptive picture for the field behavior by presenting the experimental hysteresis loops. Measurements were carried out on a nonoriented silicon steel sample of M36G26. A novel design of magnetizing test fixture based on an electromagnetic Halbach array is used to perform these measurements. Results show that the negative value of power in one loss component is a result of method of analysis, while the negative value of total rotational power loss is a consequence of faulty measurements.