The article describes the method for determining the optimal angular velocity and the number of turns of the generator winding on permanent magnets powered by a wind turbine operating in specific operating conditions according to the wind speed regime. The optimization criterion is the maximum potential of energy that can be used to charge the battery. The permissible power of the generator and wind turbine, current and battery charging voltage are accepted as limiting factors. The restriction is provided by connecting a ballast resistor to the generator output. The power developed by the turbine is determined taking into account the wind energy utilization factor, which depends on the angular velocity of its shaft and wind speed. Two variants of power limitation are compared: by limiting the angular velocity by aerodynamic means and by stopping the wind turbine. The return of energy to charging in both cases is determined taking into account the distribution of wind speeds, obeying the Weibull probability distribution law. As an example, the calculation of the possible annual power generation for charging a battery with a capacity of 200 A∙h with a voltage of 24 volts from a synchron generator with a number of poles of 48 driven by a wind turbine with a radius of 2 meters, operating in an area with an average wind speed of 5 m/s. The calculation shows that for the parameters and operating conditions of the electrical installation used in the example, the maximum annual energy output (3.3 × 103 kWh) is observed at optimal 11 turns of the winding at each of the poles of the generator. The deviation of the number of turns from the optimal one in both directions by 2 times leads, with the same dimensions of the wind turbine, to a decrease in annual energy output by 3...5 times, which is a clear proof of the need to carry out such a calculation for each specific wind turbine.

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The article considers the issues of current protection circuitry of asynchronous motors operating from the AC mains of standard frequency. It is noted that in the vast majority of cases transformer current sensors operating in idle mode (transreactors) or in short circuit mode (current transformers) are used as current sensors in such protections. Current transformers have a more stable linear "input-output" characteristic, less current and angular errors, so they are most widespread. The purpose of the work is to substantiate the parameters of the universal current transformer and methods of setting setpoint currents for the protection unit of asynchronous motors having a wide range of rated currents. It is shown that nominal currents of protection units for different groups of electric motors with the multiplicity of the maximum to the minimum nominal currents equal to four will be determined only by the number of turns and the section of the primary winding installed in each specific unit of the current transformer. Moreover, with the maximum possible nominal current for a particular design of the protection unit, which allows direct switching into the controlled current circuit without intermediate current transformers, the number of turns of the primary winding should be equal to one. Under these conditions, it is technically possible to change the nominal current of the current protection device by changing the number of turns of the primary winding of current transformers with a discrete coefficient equal to 2:1 turns, 2 turns, 4 turns, 8 turns, etc. At the same time, it is proposed to set the actuation current of the protection unit for each specific motor by discrete change in the conductivity of the load included in the secondary winding of the current transformer.

The article is devoted to the development of methods for theoretical substantiation of the permissible supply voltage asymmetry coefficient for an asynchronous electric motor operating in the steady state under nonnominal operating conditions. The core of the technique lies in the fact that the heat loss power of the electric motor operating in the steady state with the actual: load/utilization level, asymmetry degree, supply voltage is calculated. The calculation is carried out using an L-shaped equivalent circuit of the electric motor, which is connected separately to the voltage components of the forward and inverse phase sequences with the subsequent imposition of the calculation results produced by the algorithm proposed by the authors and developed on the basis of the program in the MathCAD system for each of the components. Provided that we predetermine the motor torque under voltage u, the degree of asymmetry of voltage k and angular velocity ω -М(u,k,ω); the moment of resistance as a function of degree of load z and angular velocity ω -М с (z,ω); and the steady angle speed ω y (z,k) by numerically solving the equation М(u,k,ω) -М с (z,ω) = 0. Then, we find the power of heat loss ∆Р у (u,z,k) for this angular velocity. The permissible asymmetry of the voltage k d (u,z,t) is determined by equating these losses to losses permissible under heating conditions, which are a function of the temperature t of the ambient temperature ∆Р d (t), and solving the resulting equation for the asymmetry factor of the supply voltage.As an example, we made the calculation of the parameters of the steady state of the 4A355S6U3 electric motor. According to the calculation results, the curves of the dependence of the power of heat losses on the magnitude and degree of voltage asymmetry at different values of the motor utilization/load rate were plotted. An acceptable voltage asymmetry factor is determined for these conditions.