Influence of working temperature on lossiness of dielectromagnetics
Tomasz Janta Politechnika Wrocławska, Instytut Maszyn, Napędów i Pomiarów Elektrycznych ul. Smoluchowskiego 19, 50-372 Wrocław
Quarterly No. 4, 2006 pages 62-65
DOI:
keywords: powder metallurgy, soft magnetic materials, dielectromagnetics, dielectrics, lossiness, ageing phenomena
abstract Magnetic powder composites find ever-wider use as active magnetic materials for magnetic cores of electric devices. Because of their properties and manufacturing technology, dielectromagnetics attract a great interest. They are powder composites made from soft magnetic powder with an admixture of, among others, dielectric in the form of resins, which both bind and isolate the soft magnetic particles. The properties of manufactured dielectromagnetics and their constancy over time as well as the influence of the operating conditions (e.g. temperature) or the medium (e.g. humidity) on them are the main factors, which determine the use of these materials. When the factors are examined and understood, it will become possible to design magnetic cores in such a way that the predictable changes in their properties will not disqualify the electric devices in the course of their service. In this paper changes in the lossiness of dielectromagnetics, made of soft magnetic powder ASC 100.29 with an admixture of epoxy resin Epidian 101 in the amount of 0.1 and 0.2% by weight, caused by working temperature are described. Dielectromagnetics for tests were compacted in form of ring samples with dimensions φ50xφ60x5 mm. Applied compacted pressure was 800 MPa. Samples were cured at temperature 200°C in the resistance furnace in the course of 1 hour. The lossiness of dielectromagnetics of the specimens were tested after they were stored one year in ambient conditions at a constant temperature of 100°C and (comparative series) at a constant temperature of 21°C and a constant humidity of 50%. Block diagram of the computer system for lossiness measurements is presented in Figure 1. The density and total lossiness of tested dielectromagnetics at induction 0.5 T and 1 T for frequencies 50 Hz are shown in Table 1 and in Figure 2 (at B = 1 T). Distribution of lossiness for frequencies 50 Hz are presented in Table 2 and in Figures 3 and 4. Values of eddy current loss are very small, about 3% of hysteresis loss (Table 2). The research has shown that they increase by 14% (Fig. 4) does not essentially effect on total lossiness (Fig. 2). The effect of working temperature on the lossiness of the tested dielectromagnetics is small and profitable - the total lossiness decreased about 1% (Table 1, Fig. 2). This is a proof of the high quality of the soft magnetic powder and dielectric used whose properties remain stable over temperature.