In the article schemes of power circuits of a feed of synchronous reluctance machines are considered. The features of the choice of the most rational scheme by the criterion of improved weight and size parameters are shown. It is shown that the specific parameters of electric drives have values that exceed similar synchronous electric drives by approximately 20%. Improvement of specific parameters in the agriculture electric drive can be achieved not only due to the complexity of the electric machine construction, but also due to the choice of optimal schemes of power circuits. So, in agriculture electric drives with individual sources with rectangular current form, the values of overloads corresponding to electric drives with complex (compound) rotor design.

The article presents ways to improve reliability of agricultural semiconductor frequency converters. It is shown that an increase in reliability of semiconductor converters can be achieved increasing the power reserve. At the same time, if the economic indicator is chosen as an optimization criterion, the coefficient of failure-free operation reaches no more than 0.8. In the event that resulting coefficient of failure-free operation is allowed according to operating conditions, selected criterion can be successfully applied at design stage of semiconductor converters.