FEM-Based Virtual Prototyping and Design of Third Harmonic Excitation System for Low-Voltage Salient-Pole Synchronous Generators

Virtual prototyping is a method used for the prediction of electrical machine parameters during the design stage, thus reducing the development time and cost for new machines. Based on the simulated results of the virtual prototype, the design is fine-tuned and finalized. In synchronous generators, the design of a third harmonic excitation (THE) winding is done based on the third harmonic flux generated in the air gap of the machine. Estimating the amplitude of the third harmonic flux in the air gap of a machine accurately by conventional design procedures is difficult due to the complex geometry of the machine and the nonlinear characteristics of the magnetic materials. In this paper, accurate prediction of the third harmonic flux in the air gap is done by the finite-element method, and prototyping of the machine is virtually done with the third harmonic winding inserted into the stator slots. Based on the electromotive force induced per turn, the design of the third harmonic winding is finalized, and an experimental machine with THE is developed. The effect of the THE in reducing the total harmonic distortion across the main output terminals of the generator is analyzed, and the experimental results show close agreement with the simulation results.