The Stator Winding Design And Modeling Analysis Of Soft Start Wound Brushless Doubly-fed Machine

As a new type of multi-port induction motor,Brushless doubly-fed motor(BDFM)has been simplified greatly because of its implementation of the brush free,and has the characteristics of high safety and reliability,adjustable power factor and so on.The stator of BDFM has two sets of windings with different pole pairs,namely power winding and control winding.The rotor structure is usually wound type,cage type and reluctance type,so the design of BDFM is flexible.By changing the two sets of stator winding power supply type,BDFM can work in asynchronous,synchronous,doubly fed operation state.Due to the excellent speed regulation performance of BDFM,it has a wide application prospect in wind power generation,coal mine transportation and other fields.The realization of motor soft start has always been an important research content in the field of belt transportation,because the traditional motor soft start is mostly realized by external equipment,such as inverter and other power electronic equipment.With the increase of the capacity of the motor,the price of the matching converter and other equipment increases exponentially.This will not only lead to the motor system integrated into a larger,but also make the reliability of the system low.To solve this problem,this paper presents a new type of BDFM which can realize the soft starting mode only by changing the winding connection mode.Through the specially designed stator and rotor windings,different working characteristics can be produced in the starting and normal operation states,so as to realize the soft starting of BDFM.This method not only ensures the starting performance of the motor,but also greatly reduces the comprehensive cost of the motor system.It has a good balance in practicality and economy,promotes the development of BDFM in the field of belt transportation,and provides a new idea for the realization of soft starting of the motor.The research contents of this paper mainly include the following aspects:Firstly,by summarizing a large number of domestic and foreign literature,the structural characteristics,development history and research status of BDFM are fully analyzed.This paper briefly summarizes the analysis method and parameter calculation method of BDFM,and finds the research value and shortcomings of soft start in the field of motor.At the same time,the operation principle of BDFM is introduced in detail,and the basic design idea of soft start wound brushless doubly-fed machine is introduced.Secondly,based on the principle of pole-slot combination of conventional induction machine,the general selection principle of pole-slot combination of soft start BDFM is deduced.Based on the basic design idea of soft start wound BDFM,three kinds of power windings with different structures are designed.The design method and working mode are introduced in detail.The specific slot number of each phase is selected through the slot number phase diagram,and the harmonic magnetomotive force content of each winding is analyzed.Based on the unequal turn winding,the rotor windings with compound coil are designed,which can cooperate with the stator windings and produce different working characteristics under different pole pairs of magnetic fields,so as to realize the soft start of BDFM.After that,based on the analysis of the parameter calculation and mathematical model of the conventional wound rotor BDFM,the mathematical model of the soft start BDFM considering the influence of harmonics is deduced and designed.The starting characteristics of three kinds of windings with different structures are compared and analyzed by MATLAB.Finally,the finite element model of soft start type wound BDFM is built by using the finite element software,and the winding structure of the motor is further optimized.The electromagnetic and starting characteristics of the three schemes are analyzed and compared in detail.The soft start performance of the best scheme is compared with the asynchronous start,and the prototype is made for experimental verification.The experimental results are consistent with the theoretical analysis results,which fully shows the accuracy of the analysis method and the feasibility of the design theory.