Influencies of the Slits on Magnetic Flux Density for Induction Motors Having Different Rotor Slot Geometries

There are many methods in literature for canalizing of circulating useful flux from stator core to rotor core without radial movements in induction machines. It is obvious to healing of useful flux with decreasing radial moved zig-zag flux and it increases the motor performance. Magnetic barrier, cutout and using of slits are the most used methods for improve the circulating useful flux in the motor. As seen from literature, these methods are used to improve the performances of different motor types. These motor types are, switched reluctance motors, solid rotor motors, hybrid synchronous motors and induction motors etc. In this study, slits are applied on the centers of the stator core and rotor core teeth for three phase induction machine. Slit lengths are chosen same with the stator slot lengths. Slit widths are chosen to 0.1 mm for stator and rotor cores. Applied slits are act as air gap barriers and generate a magnetic conditioning for help to decrease the radial zig-zag flux that circulates in the machine. There are 10 different rotor slot geometries are used to simulate the behavior of the magnetic field distribution for different slitted slot geometries. Comparing of the flux densities for conventional and slitted motor structures and airgap magnetic field distributions of different motor geometries are given. From this database, determining of suitable stator and rotor structure for the machine is achieved. Analyzes are conducted with the finite element method based free software FEMM. Keywords—induction motor; magnetic field analysis; rotor slot geometry; slits