| In the traditional shafting ship propulsion system,its propulsion shaft occupies a large amount of space in the ship,which reduces the utilization rate of the ship.The advent of podded propeller has effectively solved the problern of traditional propulsion shafts,but it also has defects such as easy failure and difficult maintenance.So ’the rim driven motor(RDM)appeared as a new type of marine propeller.The RDM does not have fault-tolerant ability.Combining it with a fault-tolerant permanent magnet motor,a fault-tolerant permanent magnet rim driven motor(FTPM-RDM)appears.And combining the FTPM-RDM and the shroud structure,a truncated-cone shape FTPM-RDM is proposed in this paper.Firstly,the research status at home and abroad of RDM,FTPMM and shroud device are introduced in this paper which shows that the truncated-cone shape FTPM-RDM has important research significance.The structural characteristics of the motor are analyzed.Aiming at the special shroud structure,the structural design scheme of the truncated-cone shape FTPM-RDM is given.The 3D Maxwell finite element software is used to analyze the performance of the motor with different cone angle and the selection principle of the cone angle is given.Aiming at the shortcomings of low sine degree of the induced voltage waveform of the truncated-cone shape FTPM-RDM,:the polar arc coefficient and centrifugal height of the magnet are optimized and three-dimensional finite element verification is carried out by the segmentation method.The selection principle of the two optimization parameters is given.After optimization,the induced voltage harmonic content of the motor is significantly reduced,and the cogging torque ripple is reduced.Aiming at the problem that the front side outer diameter of the truncated-cone shape FTPM-RDM is larger than traditional FTPM-RDM,which makes the fluid resistance larger,the winding self-inductance is analyzed by an analytical method,and anew type of notch thickness distribution structure is proposed in this paper.This structure keeps the winding self-inductance unchanged,reduces the outer diameter of the motor.Aiming at the problem of uneven distribution of the magnetic density of teeth,the total magnetic flux of the teeth is calculated and the optimization methods of tooth width is given.After optimization,the axial distribution of the magnetic density of the teeth is almost the same.The stability of motor operation is improved,and the size of the motor is slightly reduced.A six-phase H-bridge current hysteresis control circuit was built based on Simploler,the starting performance and fault-tolerant capability of the truncated-cone shape FTPM-RDM were verified by simulation experiments.Finally,a comparison is made between a truncated-cone shape FTPM-RDM and a cylindrical FTPM-RDM.It shows that when the electrical characteristics of the two are consistent,the truncated-cone shape FTPM-RDM has higher propulsion efficiency due to the special fluid structure design. |
