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Owing to the larger total harmonic distortion (HD) of the air‐gap magnetic field in the linear induction motors with the flat‐solid and direct‐slit secondary, the construction of V‐type secondary is proposed and investigated, to reduce the harmonic components. First, a skew factor is presented to indicate the influence of the tooth harmonic on the air‐gap magnetic field. The skew distance is a key point for the design of the V‐type secondary, and the influence of the different skew distances on the thrusts, HD, and efficiencies are analysed by the three‐dimensional finite‐element method. Finally, the eddy currents, the air‐gap flux densities, and electromagnetic forces are calculated in the linear induction motors with the V‐type secondary. It shows that the V‐type secondary can reduce the harmonic components and improve the performance. [ABSTRACT FROM AUTHOR]

Due to the influence of the switch and rail equipment, the secondary cannot be laid continuously in the linear metro. An equivalent circuit of the single‐sided linear induction motor (SLIM) is presented to consider the discontinuity of the secondary plate, and the electromagnetic characteristics of the motor with the discontinuous secondary are obtained. First, the analysis model of the SLIM considering the missing part of the secondary plate is proposed. Second, the variation of the length of the coupled region between the primary and secondary are considered by the method of approximate linearisation to correct the parameters including the primary leakage inductance, magnetising inductance, secondary resistance and secondary leakage inductance. Third, three typical cases of the relative position between the primary and discontinuous secondary are analysed, and the equivalent circuit in each case is deduced according to the distribution of the secondary magnetic motive force and air gap flux density. Then, two coefficients considering the longitudinal end effect, on the basis of the corrected secondary time constant, are proposed to correct the magnetising inductance and secondary resistance. Finally, the analytical results are verified by the results measured on the test rig of an SLIM. [ABSTRACT FROM AUTHOR]

Electromagnetic variations of the single‐sided linear induction motor (SLIM) are calculated by three‐dimensional (3D) finite‐element method (FEM) when the primary is displaced sideways from a symmetrical position. For geometrical and electrical asymmetry, a full 3D model, which considering the longitudinal and transverse end effects, overhangs of the primary windings and secondary, as well as lateral displacement, is developed. Apart from the thrust and vertical force, lateral force is produced when the transverse asymmetry occurred. Hence, the calculation equation of thrust, vertical and lateral forces in each element of the 3D FEM model and boundary conditions are presented. Air‐gap flux densities along the longitudinal and transverse directions with different lateral displacements are obtained, as well as the distortion coefficients of the air‐gap flux density is proposed. Corresponding induced currents in the secondary are predicted. Finally, the variations of the thrust, vertical and lateral forces are experimentally validated by measurements on reciprocal power‐fed test rig. It shows that the flux in between overhangs of the primary winding and secondary has great effect on the lateral force, the thrust and vertical force decrease with the increase of the lateral displacement. [ABSTRACT FROM AUTHOR]