Magnetic materials in design and construction of electrical motors

Abstract

Electromechanical steels, currently used in the manufacture of electrical machines possess high induction of magnetic saturation (Bs/spl sim/2T), low coercive force (Hc<100 A/m), and they are characterised by low total losses P (1,5/50)=1-3 W/kg. The soft magnetic composite materials are characterised by their high losses (7-10 W/kg), due to the vortex flow, stimulated by the absence of interfaces between the magnetic circuit components. In the case of polymeric bound materials, the losses due to mixing are of the order 5-8 W/kg. To gain maximum benefit from the manufacturing of small electrical machines by using soft magnetic material, it is important to choose the suitable material for every application. Excellent high frequency performance, a similar average performance for several types of electrical machines, and an important cut in the manufacturing expense (material loss, simple technology) are the main characteristics for a soft magnetic material core made electrical motor. The paper presents the comparison between two single-phase motors, with a magnetic core manufactured with laminated steels, and soft magnetic composite materials respectively. The geometrical dimensions are identical.