Electromagnetic Characteristic Analysis And Experimental Study Of Soft Starting Brushless Doubly Fed Motor Based On Compound Coil Structure

Brushless doubly fed motor is a new type of induction motor with simple structure,reliable operation and good speed regulation performance.With the development of industrial application,the brushless doubly-fed motor is not only used as a generator in the field of wind power generation and hydroelectric power generation,but also used as a motor in the field of electric power driving and coal mining and other industrial production.With the progress and maturity of control technology,brushless doubly-fed motors are widely used in the field of Variable frequency speed control.In order to improve the starting performance of motor,a soft starting method is proposed to reduce the impulse current.The core of this method is to reconstruct the stator power winding and rotor winding.The brushless doubly-fed motor with wound rotor has flexible structure,which can adjust the pitch and number of turns of stator and rotor coil as well as the connection mode to change the distribution of air gap magnetic field to improve the starting performance of the motor.Starting from the winding design of the brushless doubly-fed motor,this paper shows the whole development process of the brushless doubly-fed motor from design to parameter calculation,mathematical model building,simulation calculation,prototype manufacturing and experimental measurement.It is mainly divided into the following parts.This paper first discusses the development history and significance of brushless doubly-fed motor,and summarizes the development of ontology and control strategy respectively.In the introduction of the development of the motor body,the advantages and disadvantages of different types of rotor structure and stator structure are compared in detail,and then the winding rotor is selected as the basis to carry out the research on the soft starting method of the brushless doubly-fed motor.At the same time,the operation principle of the brushless doubly-fed motor and the power distribution of the power winding and the control winding are introduced in detail.Secondly,based on the basic operation principle of the brushless doubly-fed motor,the design concept and requirements of the power winding of the soft-start brushless doubly-fed motor are determined.In order to verify the correctness of the design theory,the paper takes a brushless doubly-fed motor with 36 slots and 2/4 poles as an example to show the design process of its power winding in detail,such as different connection modes,slot number selection method and multiple scheme generation method.Using this design idea,the design scheme of 54-slot power winding with two pairs of poles is also presented.It is verified that this method can be extended to brushless dual feeders with other number of slots,and not restricted to 36 slots.In addition,the rotor of the brushless doubly-fed motor used with stator winding is introduced,and the design scheme and operation principle are analyzed.Finally,after the connection mode and winding scheme of the motor are selected,the parameters of the motor are calculated to build a more accurate finite element simulation model.After finite element simulation,a brushless doubly-fed motor test prototype is manufactured.Based on the finite element simulation and test data,the stator current impact characteristics and the steady-state load capacity of the motor during starting and stable operation are analyzed.Then the correctness and superiority of the design idea and method of soft starting scheme are explained.