Analytical Calculation And Analysis Of Characteristics Of Linear Induction Motor Considering The Discontinuous Secondary Plate In Urban Rail Transit

Trains driven by short primary single-sided linear induction motors(SLIM)have gained advantages in rail transit due to their strong climbing ability,small turning radius,low operating noise,ability to overcome the limitation of adhesion between wheel and rail and low tunnel construction cost.The main operating conditions of the trains driven by SLIM are that the primary is completely coupled with the secondary(normal operation).However,the trains encounter intermittent areas of the secondary plate at the turnouts and corners,as well as at outbounds and warehousing.As the most important traction unit of the train,the SLIM will causes the short-circuit fault of the converter during the process of passing through the discontinuous secondary,causing irregular wear of the train wheel pair,seriously affecting the safety and stable operation of the train.As a special working condition with little relevant research so far,the process of the primary of SLIM passing through the intermittent section of the secondary plate requires electromagnetic characteristics in terms of air gap flux density,thrust and parameter variation of the equivalent circuit.The analysis lays a solid foundation for the control strategy of the primary of SLIM safely and stably passing through of the secondary discontinuous area.This article has carried out in-depth research around the above issues.The main contents of the full text are as follows:In this dissertation,the finite-elemenmt method(FEM)is used to carry out detailed and accurate calculation of SLIM.The air gap magnetic field,secondary eddy current,thrust and normal force of SLIM during normal operation and cases with differently discontinuous secondary are obtained and analyzed.And the relationship between magnetic field,eddy current and force are summed up.In addition,the process of SLIM passing through the intermittent area of the secondary plate is divided into three kinds of missing conditions,and the thrust,efficiency and the trend of self-inductance and mutual inductance of the three-phase windings are analyzed in detail.The results show that with the increament of the uncoupled region between the primary and secondary plate,the thrust and efficiency of the motor show a decreasing trend as a whole,and the self-inductance and mutual inductance of three-phase windings decrease with periodic fluctuations.Aiming at the construction of the equivalent circuit during the process of SLIM passing through the discontinuous secondary,this dissertation firstly adopts the Duncan model to construct the equivalent circuit,and analyzes the inapplicability of the equivalent circuit of Duncan during the intermittent region of the secondary plate.The distribution curves of the air gap flux density and secondary magnetomotive force under different missing conditions are derived.The correction coefficient of the magnetizing inductance in the magnetizing branch and the correction coefficient of the equivalent resistance of the eddy current loss characterizing the longitudinal end effect are derived.The equivalent circuit considering the normal operation and the discontinuous secondary are derived,and the transient change trend of the equivalent circuit parameters are analyzed.The comparison between the analytical results and the results of FEM shows that the equivalent circuit based on the Duncan model can effectively describe the transient process of SLIM passing through the discontinuous region of secondary plate.Considering that the equivalent circuit based on the Duncan model fails to fully reflect the particulars such as the transient process of the half-filled slots of the primary passing through the discontinuous secondary,three analytical methods in normal operation based on different assumptions such as the infinite length of the primary,the correction of the infinite length of the primary and the finite length of the primary are deducted,and selected the best method.Considering the influence of the half-filled slots and the exit end effect,the process of the primary of SLIM passing through the discontinuous secondary area is divided into nine special conditions.According to the air gap magnetic field of the primary and secondary coupling regions,the variation trend of the parameters in the magnetizing branch and the secondary branch is derived and analyzed.The uncoupled region between the primary and the secondary plate is mainly considered by the correction of the primary leakage inductance.The comparison of the equivalent circuit between the quasi-one-dimensional analytical theory and the Duncan model shows that the equivalent circuit constructed by the quasi-one-dimensional analytical theory more accurately describes the process of SLIM passing through the intermittent region of the secondary plate,but complexity and computation of the method are relatively large.