Development of Variable-Speed Wind Generators Using Magnetic Modulation Effects of Multiple-Barrier Rotors

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In this study, a dual-winding reluctance generator (DWRG) was developed as a new type of variable-speed wind generator. The developed DWRG consists of two stator windings (armature winding and field winding) with different pole numbers and a multiple-barrier (MB) rotor. The air-gap flux is modulated by the MB rotor, and magnetic coupling between the two stator windings is realized. The findings of the study are summarized below.1. Experimental VerificationA 1-kVA prototype machine was built, and its basic characteristics were investigated experimentally. The results showed that :(1) By changing the field current, the constant-voltage control was easily achieved over a wide range of speeds ;(2) Although the design of the prototype machine was not optimal, it was reasonably efficient ;(3) The copper loss in the field winding comprised a large percentage of internal losses, and the value of the core loss was relatively small. Therefore, reducing the copper loss in the field winding is effective in raising the efficiency.2. Development of the Basic TheoryTo predict the steady-state performance of the DWRG theoretically, a simple mathematical model was developed and verified with experimental results on the prototype machine. The developed model takes into account the magnetic saturation and core loss and enables a quantitative prediction of load characteristics from the no-load test data.3. Design ConsiderationUsing FE analysis, the influence of flux barriers on the air-gap flux was investigated. The analysis showed that increasing the number of layers of flux barriers reduces the amount of the leakage magnetic flux and that the amplitude of the main magnetic flux is dependent on the curvature radius of flux barriers to a great extent.