Magnetic Field Modulation Mechanism And Topology Investigation Of Primary Permanent Magnet Linear Motor

In order to achieve energy conservation and environmental protection,high-rise buildings and public transport are gradually popularized.Rail transport system is the indispensable equipment both in high-rise buildings and public transport.As one of the main driving components of rail transportation,linear traction motor has attracted wide attention from scholars at home and abroad because of its high efficiency,precise positioning,simple structure and small volume.In order to solve the problems of low thrust density and low reliability of existing linear motors,the principle of magnetic field modulation is introduced into primary permanent magnet linear motors,which are referred to flux-modulation permanent magnet linear(FMPML)motor for short.The effect of magnetic field modulation is used to improve the flux change rate of motor windings,increase the back EMF and enhance the thrust performance of motor.Based on the models of magnetomotive force and permeability,the working principle and topology of FMPML motor are analyzed,and the basic design method of FMPML motor is summarised.The influence of modulation ratio and slot pole number of FMPML motor on electromagnetic performance is studied.The topologies of ring type winding FMPML motor with high force density and reliability and FMPML motor with high power factor are proposed respectively.The electromagnetic performances of these two FMPML motors are analyzed by finite element method.The mechanism of high power factor in FMPML motor is revealed.The experimental platform of FMPML motor is built and the experimental research is carried out.The main research results of this paper include the following aspects:1.Based on the models of magnetomotive force and permeability,the air-gap flux density and operation principle of FMPML motor are analyzed.It is revealed that the magnetic field modulation effect can improve the force performance.The equations of power,electromagnetic thrust and cogging detent force of the motor are deduced respectively.The main parameters affecting the modulation and electromagnetic performance of the motor are determined based on the above equations,which provide a theoretical basis for the design and optimization of FMPML motor.2.A new half-Halbach array structure with different size ratios and magnetizing directions is proposed.The influence of different PM array structures on the working harmonics in the air gap flux density of FMPML motor is analyzed and compared.The mechanism of different PM array structures affecting the electromagnetic performance of the motor is revealed,such as back electromotive force(EMF),thrust density,pulsation,cogging detent force and so on.The optimum parameters of half-Halbach PM array are determined and the analysis of demagnetization is also carried out to ensure the safety and reliability of the designed FMPML motor.3.The influence of modulation ratio and slot pole number on the performance of FMPML motor is studied.The electromagnetic performance of FMPML motor under different modulation ratio and slot pole number is analyzed and compared.Finally,the optimum range of modulation ratio and slot pole number can be determined.The multi-objective optimization method is used to optimize the structure parameters and the prototype scheme of motor can be determined,which provides a reasonable reference for the optimization design of FMPML motor with high thrust density and high reliability.4.The topologies of FMPML motor with ring type winding and FMPML motor with high power factor are proposed respectively.The no-load magnetic field distribution of FMPML motor with ring type winding is analyzed.The conception and origin of ring type winding in FMPML motor are expounded.The electromagnetic performances of ring type winding FMPML motor with different pole pairs are compared.Beside,the reason of low power factor in FMPML motor with ring type winding is also studied.The no-load magnetic field distribution of FMPML motor with high power factor is analyzed to reveal the mechanism of high power factor.Finally,the electromagnetic performance of FMPML motor with high power factor is summarized,which provides necessary parameters for the establishment of mathematical model and system of motor.5.The mathematical models of three-phase static coordinate system and dq coordinate system of FMPML motor are established.The vector control principle of FMPML motor is studied.Based on the motor control system framework,the simulation model is established,and the dynamic performance of id=0 control method is studied and analyzed,which verifies the feasibility of control system.6.The experimental prototypes of a 36/42 modular FMPML motor and a 36/20 FMPML motor with high power factor are fabricated respectively.The experimental test platforms are built.The experimental research is carried out.The no-load back EMF,resistance,inductance and thrust of 36/42 modular FMPML motor an no-load back EMF and thrust of 36/20 FMPML motor with high power factor are measured.The measured data are compared with the simulation data,which verifies the correcteness of the design and optimization method of FMPML motor.