Due to the fringing effect, magnetic flux in the ait gap of the electrical machines is reduced. This leads to largered the effective air gap length. Currently, Carter coefficient is applied to compensate the slots effects. This coefficient is calculated with respect to the slots dimensions and air gap length, using Carter formulas and corresponding curves. These curves are taken by solving the two dimensional Laplas equation for voltage, and cannot be accurate (errorless) completely. Nowadays, using the FEM (finite element method) packages of numerid methods, slot effects on the air gap flux distribution are calculated carefully. In this paper using the Ansys package of FE these effects are studied Using the resulu of these studies and comparing them with carter method, the carter coefficient is modified. gap of the machine is reduced strongly in h n t of the slots, and distorted from the sinusoidal shape._.-._.__ i 1
INTRODUCTlONDesigning of the electrical machines spatially rotating one, involves the solving of some complicated electromagnetic, thermal and mechanical problems. Due to the capabilities and flexibilities of the FEM, nowadays FEM is applied in solving such problems. In this method, after the design of the geometry of the model, specifying the material types of different parts of the model and its parameters and physical characteristics, different surfaces of the model are meshed by elements suitable for the proposed analysis. Then applying the excitation and boundary conditions, the model is solved. In the FEM for analyzing of a model, type of the meshes must he chosen suitably with respect to the analysis type. Elements are Figure 1. a-Two dimensiond cut of machine and flux lines dishbution, triangular or rectangular. If the model geometrical shape is regular, the map meshing can be made, otherwise free meshing is applied Slot shape and dimensions effect in the air gap flux scattering, are studied by different researchers, such as Caner 18. 91 and Green. and different results are oroduced S t d v of b b-nux density disnibution in the air gapIn an electrical machine v a n from the effect of the slots opening and flux scanerin& having a larger permeability of the iron wre, the reluctance of each pole flux is calculated as (1). If . . ~ the slot dimensions on the flux density of the magnetic fields is returned to the beginning of the last century, where the numerical methods are not developed yet. So the results of those methods cannot be accurate completely.In this paper using the Ansys package, the effect of flux scattering in air gap between the slots, on the magnetic characteristics is studied. The results are compared with the classic methods and finally the mcdified Carter wefficient is introduced.
EFFECT OF FLUX SCATTERING ON THE FLUX DENSITYthe slots effect is considered, the core surface under each pole is reduced and the flux of each pole, having a constant ampereturn, is reduced. This difference can be applied by inducing the air gap length and the real air gap length g is compensated to a...
