Iron Loss Analysis of Doubly Salient Brushless DC Generators

The doubly salient electromagnetic machine (DSEM) is a kind of variable reluctance machine, which is different from the conventional ac electric machines. A new 24/16-pole DSEM is presented, and the configuration and operation principle are discussed. Based on the comprehensive study of the field distribution feature, the DSEM is separated into eight sections to investigate the iron loss distribution. In order to predict the iron loss of the doubly salient electromagnetic generator (DSEG), the flux density variations of each section are resolved into radial and circumferential waveforms, and Fourier transform is utilized in consideration of harmonic components. A calculation model of iron loss is established, and the coefficients are determined by the measured data at different speeds. The iron loss distribution of the DSEG is investigated. The proportion of iron loss to copper loss is further analyzed under different load conditions. Moreover, the influences of speed, air-gap length, and field current on iron loss are analyzed and summarized. Finally, the calculation and analysis of iron loss are verified by experimental results.