DESIGNING ELECTRICAL MACHINES WITH A CROSS MAGNETIC FLUX
Abstract
For new application fields of electrical machines: a motor vehicle equipped with a hybrid power installation, a direct electric drive of the ship screw, and a wind generator with a gearless drive of the electric generator, a new design of a multipole electrical machine with permanent magnets is developed, featuring a high torque at low rotation speeds. Such a machine is referred to in the literature as a machine with a cross magnetic flux or a machine with a switched magnetic flux. This machine can be used in a motor and generator modes, which are controlled by power semiconductor switches. Two standard magnetic circuit arrangements are presented, which differ from each other in the number of permanent magnets on a pole. Ring stator windings are used in the majority of cases. The length of stator pole part interacting through the air gap with permanent magnets and determining the machine axial length and the magnetic core cross sections was adopted as the basic size determining the sizes of the machine and its winding. The basic calculation formula for the basic size is obtained in the form of a fourth root from the expression containing the machine torque. All other sizes of the magnetic core and windings are interrelated with the basic size through constant coefficients. The machine model in the Matlab computer program operating as a wind generator with variable electric load is presented. When switching loading towards increase and reduction Variations of rotation speed, torque, and power triggered by stepped changes of the load toward increasing and decreasing were recorded during simulation. For the 75 kW capacity level, the characteristics of this machine and earlier known types of machines were indicated, and it is shown that this machine has the minimum weight and volume and the maximum efficiency at rotation speeds close to of 570--610 rpm. Recommendations for using this machine as a motorized wheel for a hybrid transport power installation are given.
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