Study On Finite Element Analysis Of Synchronous Brushless AC Exciter

The traditional exciter will inevitably generate arc and spark due to the presence of the brush and the slip ring on the rotor side.It is easy to generate heat and make the temperature rise too high.It is also difficult to design the ventilation and cooling of the motor.The brushless AC exciter studied in this paper adopts the brushless excitation method,which has two advantages in technology: First,as the capacity of the generator increases,the excitation current also increases,and there are no brushes and slip ring components.The excitation current is not limited by the increase and is suitable for large steam turbine generator sets.Second,the rotor rotates synchronously with the rotary rectifier,eliminating spark,friction loss,heat and noise caused by commutation,and is also suitable for working in special environments like explosives.In this paper,the analysis method and basic structural theory of synchronous brushless AC exciter are described in detail.Aiming at the complexity of the iron core structure of the brushless AC exciter and the influence of the saturation characteristics of the ferromagnetic material,the finite element analysis of the brushless AC exciter is carried out by the method of field-path combination and the finite element software Ansoft Maxwell.Specific research was conducted on setting,splitting,and post-processing.Establish a transient field to calculate the no-load voltage and obtain a no-load characteristic curve.The external circuit is built to simulate the rated load,and the magnetic field distribution and air gap magnetic density under different working conditions are obtained,and the load excitation current under the rated working condition is calculated.The calculated fundamental potential is consistent with the measured results,which provides a theoretical basis for the design of electromagnetic fields of such motors.This method has practicality and can provide reference for the calculation of the excitation current of a general AC exciter.In this paper,the electromagnetic design process of a 28 kW synchronous brushless AC exciter is introduced in detail,the specific parameters of the motor are listed,and the electromagnetic relationship inside the motor is analyzed.Finally,according to the principle of brushless AC exciter and finite element calculation,Maxwell 16.0 is used as the development platform,and the Visual Basic for Application(VBA)program development language is used to model,add materials,apply excitation,split and post-process the motor.Conduct secondary development.The stator winding,the magnetic pole and the rotor slot in the modeling of the brushless AC exciter are parameterized,and have the function of one-key solution and automatic splitting.Excel-based development platform,design visual interface,strengthen human-machine information interaction,reduce repetitive steps,improve designer efficiency,and shorten motor design cycle.