Three-dimensional finite element analysis of slitted reaction plate in linear induction motor

While a solid plate is usually adopted to the reaction plate of the linear induction motor (LIM), slits are often introduced to the plate in order to obtain the higher thrust force by enforcing eddy currents effectively. In this paper, we investigate the slit effect to find a suitable configuration of slits by the three-dimensional finite element analysis with A-φ method, and we propose a face-elements procedure with double nodes for φ at the slit to express its infinitesimal width. We also adopt a current-sheet expression, which consists of three regions for primary winding MMF, that is given by diamond coils. Based on above approaches, we evaluate the slit effect in the LIM, and compare it with the experimental data to conform the validity of the methods, resulting follows; (1) Number of slit per slot-pitch is required more than 4 for obtaining sufficient performances. (2) Preferable slit length is a little bit longer than the stator width. (3) A belt of no slit region in the middle part of the reaction plate is proposed from the structural point of view. However, its width should be less than 40% of the stator width to enforce eddy currents effectively.