Research Of The Match Between 3～(rd) Harmonic And Excitation In Synchronous Generator

The electromagnetic design of main machine, analysis and calculation of harmonicmagnetic field and the optimization design for harmonic excitation system have beensystematically researched in this paper, and the method for matching between 3rdharmonic and excitation system is given, so the problems, which puzzle the designersa long time, are resolved.The process of secondary development for ANSYS is introduced, and the detailcomputation method and the key source code of the interfaced program, which isbased on Teeth Flux Method and for computing electromagnetic field, are instructedin this paper. The program is convenient, computing quickly, and versatile to use thisprogram to analyze electromagnetic field of generators.The Three Section Method has been educed according to principium of Fourierseries. It is a new method which specialized for analyzing 3rd harmonic magnetic fieldperformance, and it is also the basic theory to adjust and control the 3rd harmonicmagnetic field. According to Three Section Method, a pole pitch is divided into 3sections, and each section was researched separately. The relative reluctance of eachsection is the key factor to affect the 3rd harmonic magnetic field. But the relativereluctance of each section always varies with the saturation variation. It is reasonableto adjust the 3rd harmonic magnetic field by adjusting the relative reluctance of eachsection. The affectings of the main factors such as air-gap, eccentric pole and poleshape are analyzied by using Three Section Method.The design of harmonic winding was explained in this paper, and how to meet therequirement for enough output power and good waveform of harmonic winding wasincluded. From the equivalent circuit of 3rd harmonic excitation system, thecalculating method of harmonic winding reactance is introduced, then the turns of 3rdharmonic winding was decided, so that the output power can match the excitationsystem well. According to the sinusoidal winding theory, a new type of harmonicwinding is designed, and the winding can weaken the higher harmonics well andmake sure its voltage waveform can meet the requirement of AVR.The accuracy and reliability of the calculating method used in this paper are proved by the experimentations. A design example of a 3rd harmonic excitationgenerator was given, and the theories and methods offered in this papar were provedby the example.