End Effect And Characteristic Analysis For Linear Doubly Fed Machine With Nested-loop Secondary

In order to gain improving climbing ability of trains,reduced turning radius and lower running noise,more and more linear machines are applied in the field of rail transit.The linear doubly-fed machine has a good application prospect in this field due to its technical advantages such as adjustable power factor,diversified operation mode and energy regenerative braking.At present,some scholars have carried out research on this kind of machine.The analysis model and method of the rotating doubly-fed machine are adopted in the research process,which is not conducive to further research and application of the machine.In order to solve the above problems,the end effect of the machine is analyzed in depth.The structure characteristics of linear brushless doubly fed machine is introduced firstly.Then,taking the basic condition of average electromagnetic thrust generated by linear machine as the entry point,expounds the working principle of the machine from two aspects of harmonic generation mode and stable operating condition and introduces a variety of operating modes.Then from the perspective of one-dimensional field,the mechanism of the longitudinal end of linear machine is analyzed and the winding analysis method of linear machine considering the influence of longitudinal end is proposed.And the inductance of the motor is calculated.Finally,the mathematical model of the motor is established,and the operation characteristics of the motor in asynchronous,synchronous and double-fed operation modes are analyzed by comparing with the equivalent brushless double-fed machine combining the finite element software.The analysis shows that the end effect of the linear doubly fed machine with nestedloop secondary will lead to the direct coupling between the power winding and control winding.The direct coupling will make some input power pass directly between the two sets of windings as transformer excitation power.It can cause the thrust ripple and make the performance of the machine worse.