Research On Dual Consequent Pole Transverse Flux Linear Motor

The main flux path of the transverse flux motor is perpendicular to the direction of motion,which realizes the decoupling of electrical loading and magnetic loading.The force density of the motor can be further improved by reducing the pole distance and increasing the number of poles.Transverse flux linear motor integrates the feature of high force density of the transverse flux motor and the feature of directedly driven load via linear motion of the linear motor,which is especially suitable for low-speed linear direct-drive applications.In order to solve the problem of insufficient space utilization in the traditional transverse flux linear motor s,a dual-consequent-pole transverse flux linear motor(DCP-TFLM)with double-side excitation structure is proposed in this paper.The basic structure configurations,mathematical model,design method,thrust force characteristics and temperature rise characteristics of the DCP-TFLM are studied.Based on the principle of minimum reluctance,the flux distribution of primary and secondary magnets under no-load condition is analyzed.The results show that both primary and secondary magnets can produce effective flux which is cross linked with the winding in the DCP-TFLM.The air gap magnetic field of the motor is analyzed by using the method of air gap magnetic potential-permeance distribution method.The distribution law of the air gap flux density with the movement of the mover is obtained.It is found that the average value of the air gap flux density changes periodically with the displacement of the mover.The magnetic circuit method is used to analyze and calculate the main inductance and leakage inductance of the motor,and the distribution of the winding inductance with varied current amplitudes in an electric cycle is calculated by the finite element method.The voltage equation,thrust equation and motion equation of the motor are derived,and the mathematical model of the DCP-TFLM is established.The air gap magnetic field distribution law is obtained by analyzing the no-load air gap magnetic field of the motor by three-dimensional finite element method.Combined with theoretical calculation,the air gap magnetic field modulation coefficient of the motor is defined to describe the influence of permanent magnet magnetic field and air gap permeance distribution on the average air gap magnetic density amplitude.The influence rules of pole pitch,air gap and magnet thickness on the air gap magnetic field modulation coefficient are summarized.The transverse flux leakage coefficient is adopted to consider the influence of magnetic flux leakage when the main flux propagates along the transverse plane.It is found that the transverse flux leakage coefficient is mainly affected by the air gap length.The variation law of the transverse flux leakage coefficient under different air gaps is summarized.An electromagnetic design method based on the maximum thrust density is proposed.The main dimension parameters,primary parameters and secondary parameters of the motor are analyzed respectively,and an experimental prototype is developed.The electromagnetic force characteristics of the DCP-TFLM are studied,and the characteristics of detent force,reluctance force and electromagnetic thrust are analyzed.Because the permanent magnets on the adjacent primary teeth of the motor are staggered by a pole pitch,the electromagnetic characteristics on the primary teeth have the characteristics of staggered complementary.The distribution characteristics of no-load flux linkage and back EMF under the staggered complementary characteristics are studied.The influence of permanent magnet thickness and tooth width coefficient on the harmonic distribution in the back EMF is summarized.According to the different generating mechanism of the detent force,the distribution characteristics of the cogging force and the end force of the motor are studied by using the characteristic analysis method based on Fourier series,and the influence law of the main structural parameters on the motor detent force is summarized,which provides a theoretical basis for weakening the detent force of the motor.It is found that in the DCP-TFLM,the reluctance force mainly produces thrust fluctuation and has no contribution to the output thrust.Compared with traditional transverse flux linear motors and permanent magnet synchronous linear motor,the overload capacity and thrust density characteristics of the DCP-TFLM are studied.The results show that the overload capacity of the DCP-TFLM is poor,but it can obtain larger thrust under a low current density.In the DCP-TFLM,there are windings and permanent magnets in the primary side at the same time.Too high working temperature will affect the insulation of windings and the performance of permanent magnets.The time domain method is used to calculate the core loss,so that the influence of motor speed on the core loss distribution can be taken into account.The distribution of motor loss under different current density and different mover speed is studied.The calculation method of the heat transfer coefficient of the motor is analyzed,and the expression of the heat transfer coefficient of each heat transfer surface is given.Through the calculation of the temperature field,it is found that the temperature rise is mainly concentrated on the primary winding,and the temperature distribution is the same on the primary core and the primary permanent magnet.