Phase Displacement Characteristics of a Parallel Hybrid Excitation Brushless DC Generator

The article presents theoretical analyses and comprehensive simulations on the phase displacement characteristics of a parallel hybrid excitation brushless DC generator (HEBLDCG). The HEBLDCG, which consists of the permanent magnet (PM) machine part and flux modulation machine part, operates at the unity displacement factor due to the diode rectifier. The PM flux and wound field flux are coupled at load because the armature windings of two parts are in series connection. By the analysis of the armature reaction, the phase displacement between phase voltage and phase current of each part is revealed. It is further deduced that the phase relationship between two parts is determined by the saliency ratio and the "displacement characteristic current" which is defined as the ratio of the fundamental electromotive force at no-load and the d-axis reactance. Based on this, the mode division method from the view of power and loss balance is proposed. These comprehensive operation modes, indicated by the internal power flow, facilitate a constant output voltage and power of the HEBLDCG under variable loads and operation speeds. Finally, the experiments verify the analyses at the constant output voltage operation.