The aim of the work is to develop a method for determining the mechanical power of DC mo-tors when they are powered by semiconductor converters, since the harmonic components of the armature current do not create a torque on the shaft. This means that at the nominal electric power of the motor, it is necessary to reduce the mechanical power to ensure the nominal tem-perature regime of the armature winding. The aim is achieved by solving the problem of deter-mining the dependence of the mechanical power of the motor on the armature current pulsations factor, the value of which depends on the control parameter of the thyristor or transistor con-verter, on the inductance of the armature circuit and the load current. As a result, it was pro-posed to express the dependence of the mechanical power in terms of the allowable mechanical load factor, which, in turn, depends on the armature current pulsations factor. The method is as follows: 1) on a computer model determine the armature current pulsations factor; 2) determine the allowable mechanical load factor and the allowable mechanical power. The novelty of the work lies in the fact that the expression for determining the allowable mechanical load of DC motors with polyharmonic power has been further developed, which, unlike the known ones, contains the square of the armature current pulsations factor. An example of the practical use of the proposed method for calculating the allowable mechanical power of DC motor when pow-ered by single-phase thyristor rectifier.

The purpose of the article is to obtain a ratio for determining the reactive power of induction motors when powered by semiconductor converters. The task is to determine the dependence of reactive power on control parameters of the converters. The research method used is computer simulation of electric drive based on Fryze power theory for non-sinusoidal currents. The result is the obtained expression for the calculation of reactive power, which takes into account the rated idle current of the motor with sinusoidal power supply and the type of converter, due to introducing special coefficients. Numerical values of the latter, depending on the control parameter, are obtained on computer models with their subsequent approximation. The scientific novelty of the research is in the further development of Fryze power theory in the direction of decomposition of non-sinusoidal current components using computer models. The practical significance is the obtained expression for determining the reactive power of an asynchronous electric drive with a thyristor voltage converter, on the basis of which the capacity of compensating capacitors is calculated to increase its energy efficiency.

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