Vernier Pseudo-direct-drive Permanent Magnet Machine:Research And Design

In modern industry,many applications put forward the requirements of low speed and large torque for motor system.The traditional way to realize the low speed and high torque is to use the gear box with the permanent-magnet motor,but the gearbox usually brings noise,vibration,mechanical wear and other problems,resulting in the increase of the system volume and the decrease of reliability.The coaxial magnetic gear uses magnetic force to realize torque transmission,so as to avoid the problems caused by mechanical contact.Vernier pseudo-direct-drive permanent-magnet(PM)machine is a kind of magnetic field modulation machine which uses the magnetic gear effect.It couples the magnetic gear into the motor and has the advantage of high torque density.It is suitable for direct drive applications requiring low speed and high torque.The research work and achievements in this thesis are as follows:1.The principle of magnetic field modulation,the structure of Vernier pseudo-direct-drive machine,the relationship of slot pole matching and the working principle are introduced.The air gap magnetic field of the motor and the method to find the maximum torque output of the machine are described.2.On the basis of an original design,the rotor structure of the machine is improved,and the torque density of the motor is also improved.This thesis proposes a high-speed rotor's flux focusing structure,and compares the flux focusing structure with other structures to study their impact on the torque.The effect of different structure of low-speed rotor on the output torque of the machine is also compared,and the demagnetization of the PM is checked.The span of the armature winding is reduced and its coil coefficient is improved.The electromagnetic finite element method(FEM)simulation shows that the torque density of the active length of the motor can be increased to 173.9Nm/L when the current density of the slot is 2.25A/mm~2(RMS).3.A prototype of the Vernier pseudo-direct-drive machine is made.The mechanical structure of the prototype and the fixture used in the assembly of the prototype are designed.The principle of selecting materials or selecting type of parts is introduced.The assembly method of the prototype is introduced.The problems encountered in the design and manufacturing of the prototype are analyzed.The back EMF of the prototype shows that the torque density of the effective volume of the motor should be higher than 112Nm/L.The prototype is tested and the possible causes of the errors are analyzed.