Calculations of the losses and thermal operation conditions for controlled alternating-current drives

Abstract

A survey of methods of calculating losses has been proposed for a class of controlled ac drivers that work under extreme conditions with arbitrary control laws of currents and configurations of magnetic systems for electrical machines. It is shown that the existing methods have low calculation accuracy for the considered class of electric drivers (error up to 30%). The results of calculations by the finite-element method and the experimental data of simulations of thermal conditions and losses using 3D models, in which an electromechanical converter is regarded as a system with distributed parameters, have been considered; moreover, the parallel calculating algorithms have been used. For example, the calculations of losses in the 3D models of a field-regulated reluctance machine have shown that the discrepancy with the experimental data is not higher than 2%. Note that the main share of losses in steel is eddy currents. The results of calculations by numerical methods using 3D models allow one to determine the losses in controlled ac drivers for nonsinusoidal control laws of phase current of the stators with complex configurations of the magnet system of the electromechanical converter. For the considered class of electric drivers, the largest share of losses (from 60 to 80%) is eddycurrent losses.