Research On Counter Rotating Double Rotors Axial Flux Permanent Magnet Synchronous Motor

In recent years,countries around the world have increased their efforts in marine exploration.The safety,stability and driving efficiency of marine equipment such as ships and submarines depend on the driving mode to a large extent.The driving efficiency of counter rotating propeller is higher than that of single propeller.In this paper,a counter rotating double rotor axial flux permanent magnet synchronous motor for driving counter rotating propeller is studied.The motor has two rotors,one stator and one set of winding.The two rotors are respectively connected with the propeller.The motor only needs one driving controller.Compared with the existing driving mode,this mode greatly reduces the cost.The motor adopts a flat disc structure,which has the advantages of compact structure and small volume.The more outstanding advantage of disc structure is that the rotor structure size on both sides of the stator is exactly the same.The energy output of the motor is divided into two parts,and the same rotor size can ensure the average energy distribution of the motor.The disadvantage of axial flux motor is that there is axial force.Especially when there is stator core,the axial force will increase rapidly.The research contents of this paper are as follows:Firstly,the basic structure of the motor is introduced,and the structural characteristics of the ring winding in the same rotation and opposite rotation are analyzed.The interaction between the permanent magnets on both sides of the rotor was studied by adding a magnetic isolation material to the yoke of the stator core.Because of the randomness of the rotor position,the influence of the initial position of the rotor on the motor is analyzed.The results show that the power of the motor is the largest when the two rotors are in the same position.Secondly,the equivalent magnetic circuit model of the motor is established.The concept of variable magnetic resistance is introduced.The change of rotor position is represented as the change of magnetic resistance.The periodicity of the magnetic circuit is analyzed accurately,and the parameters in the model are calculated.The reason of cogging torque is analyzed,and the expression of cogging torque is deduced.Combined with the disc structure of motor,a topology structure of reducing cogging torque is proposed.The axial flux motor has large axial force.The influence of air gap length on axial force and back EMF is analyzed by finite element software.Thirdly,a kind of concentrated winding is proposed to generate the reverse rotating magnetic field.The characteristics of the ring winding and the concentrated winding are studied,including how the ring winding produces a better trapezoidal wave and how the concentrated winding adopts the slot pole coordination.This paper analyzes the speed and torque changes of the motor under different loads,studies the overload capacity of the motor,and discusses the adjustment mode of the motor when the two rotors of the motor are under unbalanced load.For the concentrated winding,a topological structure is proposed,which can effectively reduce the flux density of the yoke of the stator core.Under the same flux density,the structure can reduce the axial size of the stator core and improve the utilization ratio.Finally,the consequent pole structure is introduced,which can reduce the use of permanent magnet.Based on the comparative analysis of the three types of consequent pole,the results show that the traditional consequent pole structure has the highest utilization rate of permanent magnet.Based on the basic theory,this paper analyzes the reason why the consequent pole motor has good demagnetization performance.