Efficiency improvement of a doubly salient-pole homopolar machine with powder iron core

This paper reports efficiency improvement of a doubly salient-pole homopolar machine with powder iron core. Powder iron core is composed of the metal magnetization powder with resin. It has advantages of low cost, isotropic magnetic property for three dimensions, a high flexibility of design, and low eddy-current loss at high frequency. This paper shows characteristics and performance comparisons between test machines composed of powder iron material and laminated silicon steel. Both machines are designed under the same specification except core material to evaluate the difference in materials. Experimental results demonstrate that the maximum efficiency is improved by about 1% at 9,000 r/min. In addition, it is shown that the machine efficiency can be influenced by flux pulsation in the thrust direction, through the three-dimensional (3-D) finite element method (FEM) analysis.