РОЗРАХУНОК МЕХАНІЧНОЇ ХАРАКТЕРИСТИКИ АСИНХРОННОГО ДВИГУНА ПРИ НАЯВНОСТІ В НІЙ МІНІМАЛЬНОГО МОМЕНТУ

Abstract

Problem Asynchronous electric motors (AEs) are the most common among all electric motors. This is due to the simplicity of design, high reliability, relatively low cost, better weight and overall performance, etc. The asynchronous electric drive, which has a vector control based on modern static converters with microprocessor controllers, is especially widespread now. One of the most important characteristics of the engine is its mechanical characteristics. Based on the knowledge of the dependence of the moment on the electric motor shaft on its speed of rotation in various modes of operation, it is possible to implement high-quality and efficient control. Goal. The goal is conducting the analysis of operating modes of the asynchronous motor with the calculation of its mechanical characteristics in the presence of a minimal moment in it. Methodology. Analytical methods of research, methods of the theory of electric machines and electric drives are used, as well as methods of calculating electric circuits. The method of calculating the mechanical characteristics of AE in the presence of a site with a clearly expressed minimum torque is considered. Results. The analysis of the AE is based on its G-shaped replacement scheme. The mechanical characteristics of AE in different modes of operation were considered and analyzed in details. The mechanical characteristics of the AE were calculated in the presence of a minimal moment in it. It is determined that the value of the critical slip depends on the value of the active resistance of the rotor circle. Since the current of the motor is proportional to the voltage in the first stage, and the moment is the supply voltage squared, therefore, the characteristics of the voltage drop change both qualitatively and quantitatively. Originality. The current value of the moment of the AE depends on the square of the supply voltage, the active and inductive resistance of the windings of the rotor and the stator with the given values of slip and synchronous angular velocity. For all values of the voltage, the critical velocity (critical slip) does not change, that is, it does not depend on the voltage value. The magnitude of the moment varies significantly with the change in voltage. Practical value. In real conditions, all industrial networks may be subject to voltage, therefore, it is necessary to continuously monitor how significant it is to reduce the maximum and starting moments of the drives when reducing the voltage and how much they meet the demands of the technological process. If the control of a traction electric drive based on an electric motor is considered, the fact that the voltage from the energy storage will vary with the discharge should also be taken into account. Consequently, there will be a change in both the starting and the maximum moment that this drive can develop.Keywords: asynchronous motor; mechanical characteristic; minimum torque; Clause formula; traction electric drive; electric car; electric drive system.