AC Loss Calculation and Analysis of Hollow Conductor for Doubly Salient Brushless DC Generator

The hollow conductor has attracted attention in variable reluctance machines (VRMs) working in harsh environment due to its good heat dissipation performance. The abundant harmonic content of the magnetic field in the slot of VRM and the complex structure of the hollow conductor make ac loss characteristics of the hollow conductor complex. Accurate and fast ac loss calculation is necessary to optimize the efficiency of VRM and provide the basis for thermal design. The doubly salient brushless dc generator (DSBLDCG), as the VRM, is analyzed in this article. First, the ac loss of the hollow conductor under a uniform alternating magnetic field is modeled numerically. The loss characteristics of hollow conductor in DSBLDCG are obtained by combining the analytical model and the simplified finite element (FE) model. Second, the refined FE model of DSBLDCG with the hollow conductor winding is established to verify the proposed method, and the influence of different structural parameters and operating conditions on the ac loss of the hollow conductor is also analyzed. Finally, the ac loss test experiment is designed for experimental verification.