Optimization Analysis Of Thrust And Quantity Of Permanent Magnet Of Submersible Halbach Tubular Permanent Magnet Linear Motor

In order to further improve the average thrust of the tubular permanent magnet linear synchronous motor(TPMLSM)and reduce the cost of the motor,this paper optimized the maximum average thrust of TPMLSM under different magnetization modes based on sensitivity analysis.Based on the results,a new type of TPMLSM(Halbach TPMLSM-I)is proposed to reduce the thickness of the radial magnetization PMs.This structure can keep the average thrust and reduce the quantity of PMs.The main research contents and achievements of this paper mainly include the following aspects:Firstly,the basic structure and principle of TPMLSM are introduced.The motor thrust formula shows that the motor thrust is closely related to the motor volume,air gap magnetic density and armature winding current Then,taking the Halbach TPMLSM model as an example,the magnetic circuit model of the motor is established,and the relationship between the size change of TPMLSM and the air gap magnetic density is analyzed,which provides a theoretical basis for the subsequent size optimization.Secondly,the sensitivity of different size parameters to the average thrust of TPMLSM is analyzed.According to the results of sensitivity analysis,the average thrust of three TPMLSM is optimized,and more permanent magnet is used.The average thrust of TPMLSM magnetized by Halbach is the largest,but the amount of permanent magnet is also the largest.Then,Halbach TPMLSM-I is proposed,which reduces the thickness of radial magnetized permanent magnet.It is concluded that Halbach TPMLSM-I can reduce the flux leakage and the magnetic resistance of the permanent magnet.Afterwards,the sensitivity analysis of different size parameters and the optimization of the average thrust are carried out to reduce the consumption of permanent magnet without reducing the average thrust,thus reducing the production cost of the motor.In addition,Halbach TPMLSM-I is almost the same electromagnetic performance as the traditional Halbach TPMLSM.Finally,the split ratio,the permanent magnet length and thickness of Halbach TPMLSM with double-layer and unequal-length axially magnetized permanent magnets(Halbach TPMLSM-Ⅱ)and Halbach TPMLSM(Halbach TPMLSM-Ⅲ)which replaced half of the radial magnetized permanent magnets with a magnetized core(Halbach TPMLSM-Ⅲ)are optimized.The influence of the the permanent magnet size on the average thrust of the motor and the amount of permanent magnet are analyzed.The results show that compared with Halbach TPMLSM-Ⅰ,the lengthening of the lower axial magnetized permanent magnets of Halbach TPMLSM-Ⅱ is not beneficial to increase the average thrust,and the quantity of PMs and manufacturing costs are increased.Halbach TPMLSM-Ⅲ reduces the amount of permanent magnets by adopting a magnetic core structure,but the average thrust is reduced.When the size of the motor’s primary iron core is unchanged,changing the motor pole distance can simultaneously reduce cogging force and end force.Among them,reducing the pole-pitch is better than increasing the pole-pitch to suppress the magnetic resistance of the motor.