Experimental Study of Steady State Performances about Brushless Doubly-Fed Machine of Cage Rotor with Public Bar and Public End Ring

Brushless Doubly-Fed Machine (BDFM) has three different cage rotor structures, which includes without public bar and public end ring, with public bar but without public end ring, with public bar and public end ring. At present, the theoretical analysis and experimental verification of the steady state performances about the first and the second cage rotor structures are researched. However, the cage rotor structure with public bar and public end ring is still at the stage of theoretical analysis, the prototype and its experimental study of the steady state performances are not reported yet. For this purpose, the steady state performances, such as load changing, speed control and power factor changing at different steady operating states for a BDFM prototype of cage rotor with public bar and public end ring are tested and studied in detail. According to the different power supply modes of two sets of BDFM stator windings, the concepts of "normal mode" and "abnormal mode" are proposed. And then, the experiments of the different steady operating states at the "normal mode" and the "abnormal mode" are implemented and compared. The results show that the magnetic field modulation and pole number conversion function of the prototype can be realized by the cage rotor with public bar and public end ring. This rotor structure is rugged and feasible, but the steady state performances of the same operating state at "normal mode" and "abnormal mode" are quite different.