DIMENSIONING OF THE INDUCTOR’S POLE SYSTEM OF CONVERTER-FED SYNCHRONOUS GENERATORS WITH PERMANENT MAGNETS

Abstract

The system of the magnetic circuit equations of a synchronous generator excited from permanent magnets, which defines the magnetic flux in the air gap as a function of the magnetomotive force (MMF) of the permanent magnets in the design mode, as well as the no-load and short-circuit modes is given. When taken in combination with the supplementing it correlations between the electromagnetic parameters of the generators and coefficients, this system of equations can be transformed into a system of equations linking the dimensions of the generator pole system with the electromagnetic loads in the design and short-circuit modes using which it becomes possible to determine the permanent magnet dimensions at which the electromagnetic load values adopted at the stage of defining the major dimensions of the designed generators are achieved. The article differs from the previously published materials in presenting dependencies between the electromagnetic parameters of electric machines that have never been used in designing them, or were used, but reflected them to insufficient detail. The list of such dependencies includes an analytical expression for determining the magnetic flux leakage factor linking the values of this coefficient with electromagnetic loads, and the dependences of generator short-circuit current ratio and direct-axis reactance on the electromagnetic loads and pole system geometry. As regards electromagnetic loads, the choice of their values in the design mode in designing electrical machines with permanent magnets can be made based on their application fields according to the recommendations developed for solving typical problems concerned with designing electrical machines for general industrial use, motor vehicles, aircraft electric machines or electric machines that are used in other fields of technology, provided that these recommendations are drawn up as applied to solving the same tasks that are set forth before the developer of a particular electric machine and as applied to the same cooling system that it is supposed to be used in this machine. The dependences presented in the article open a possibility to more accurately determine the sizes of not only the generator pole system, but also the sizes of all its active part. The obtained equations interconnecting the dimensions of the generator's pole system with permanent magnets with their electromagnetic parameters, enable the designer to use, in determining the size of their armatures and winding data, the same equations and in the same sequence as when determining the size of generators with electromagnetic excitation. The algorithm for determining the size of the active part of generators with permanent magnet excitation, taken in combination with the algorithm for determining the size of their pole system described in the article, becomes is more sophisticated as compared with the algorithms currently used in designing these machines. As an example of using the obtained analytical dependencies in engineering calculations, the final part of the article presents the results of determining the sizes of the inductor pole system of a particular generator excited from with permanent magnets.