Analysis Of Fundmamental Theory And Design On Disc Contra-rotating Pm Synchronous Motor

In order to drive the contra-rotating propellers of the surface and underwater watercraft,this paper proposed a new kind of electric propulsion mode in this paper,which adopted a permanent magnetic disk type contra-rotating motor's rotors to drive the contra-rotating propellers.The motor has the advantages of simple structure,compact and light,which make the original propulsion system volume reduced and system weight lightened.This motor only need a set of three-phase inverter to drive,cost saving.The whole system has the advantages of high reliability because of no brush,commutator and gear.The stator of the motor adopts slotless structure,so the output torque ripple and vibration noise of the motor was very small.Based on the above advantages,the new motor will be widely used in the water surface and under water watercraft.Therefore,the basis of the theoretical study will be divided into the following several points in this paper:First of all,the structure characteristics and operation principle of the contra-rotating motor are discussed in detail.The structural characteristics of the contra-rotating motor mainly concern the stator and double rotors.For one thing,the stator core adopts slotless disc structure,winding adopts cross-surround structure,a set of winding achieves two contra-rotating magnetic field.For another thing,double rotors with the fan-shaped magnet magnetized in parallel,which have disc symmetry structure,are easy to be controlled.The operating principle of the contra-rotating motor is:the two contra-rotating magnetic fields produced by one stator pull the double disc type rotors to rotate and output mechanical energy.Secondly,the electromagnetism relationship of contra-rotating motor was introduced mainly.Firstly,due to contra-rotating motion of the double rotor,it would cause the unfixed magnetic circuit of the motor,which is magnetic circuit in series,magnetic circuit in parallel and equivalent magnetic circuit,on this basis,getting equivalent magnetic circuit model of each magnetic circuit and summing up the characteristics of each magnetic circuit.Secondly,the different initial position of double rotors will lead to the different phase of EMF.In order to get the maximum total EMF,we must ensure that the two disk type motor units' EMF have the same magnitude and phase.Through the sharing of stator core and winding,the relation of electromagnetism and vector of the contra-rotating motor are given.Then,the essence of contra-rotating motor was summarized:the two disc type motor units are compound into one motor by a single stator structure.Then,the simulation model of the motor is established by finite element analysis software Opera.The existence of two contra-rotating magnetic field at two side of stator winding and the characteristic,namely the magnetic circuit of the motor is changed are verified.Static simulation:the double air gap magnetic density of the motor and magnetic cloud diagram of each part of the motor are analyzed;the rationality of the design of the motor is verified.Transient simulation:the maximum no-load back EMF waveform and double rotor torque waveforms are analyzed too.The conclusion that the influence to motor caused by the different winding end length could be neglected was summed up.Finally,through the previous theoretical analysis,two 2.2 kW prototype motors were designed and fabricated.Then an experimental platform was established.The no-load EMF,torque and the waveform of position angle were tested.The theoretical analysis and experiments on a prototype machine verify the correctness and effectiveness of proposed machine.