Abstract
This thesis presents the development of a novel three-phase Self-excited Synchronous Reluctance Generator (NSynRG) with a slitted-rotor core as a potential candidate for an off-grid wind power generation. The rotor of the proposed Self-excited NSynRG has a slitted rotor core to improve selected vital performance parameters namely the average torque and torque ripple. For optimal performance, the slitted-rotor core has been designed and optimized using the Genetic Algorithm (GA) technique for minimal torque ripple and maximum average torque. The SynRG with a slitted-rotor core was modelled using a two-dimensional (2D) Finite Element Method (FEM) to study the electromagnetic performance of key parameters of interest. To validate the Finite Element Analysis (FEA) results, a prototype of the SynRG with a slitted rotor was tested in the laboratory. The stator frame of the prototype was based on the stator frame of a conventional 5.5-kW induction machine of NEMA frame number 132M. The main dimensions of the squirrel cage rotor were used to design the proposed rotor with a slitted core. The novel rotor with a slitted core was constructed of steel of type M400-50A. The SynRG was tested for unity, lagging, and leading power factors for no-load and load operation. To evaluate the capability of the SynRG with a slitted-rotor core to operate in a wind turbine environment, the machine was modelled and simulated in MATLAB/Simulink for dynamic responses. The FEA results revealed that the SynRG with a slitted-rotor core, compared with the conventional SynRG with the same ratings and specifications, reduced the torque ripple by 24.51%, 29.72%, and 13.13% when feeding 8 A to a load with unity, lagging, and leading power factors, respectively. The FEA results also evidence that the induced voltage on no-load of the SynRG with slitted rotor-core, compared with the conventional SynRG of the same ratings and specifications, increased by 10.77% when the auxiliary winding is fed by a capacitive excitation current of 6 A. Furthermore, the same results evidenced that, with a fixed excitation capacitive current of 6 A, the effect of armature reaction on the SynRG with slitted
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rotor core is demagnetizing when operating with load currents having a lagging power factor and magnetizing when operating with load currents having unity and leading power factors. The experimental results show the same patterns for different excitation capacitance values. It is also observed
that increasing the value of capacitance attached to the auxiliary winding of an NSynRG with a slitted-rotor core steadily increases the average torque and power factor while slightly decreasing the efficiency. The Matlab/Simulink results show that the SynRG with a slitted rotor core has a quicker dynamic response than the conventional SynRG, making it ideal for an off-grid wind generation system. However, a well-designed pitch-control mechanism for the wind turbine is necessary to account for changes in wind speeds.