Investigation of energy parameters of a compensated asynchronous motor in the mode of repeated short-term starts

Abstract

The study is devoted to energy efficiency management of induction motors with a short-circuited rotor of low and medium power and is a continuation of the development of the theory of compensated asynchronous motors. The purpose of the study is to substantiate the influence of the capacitance value of the internal capacitive reactive power compensation of an asynchronous motor in starting mode. The performed mathematical modelling of the compensated asynchronous motor allowed investigating quasi-transient electromagnetic processes considering the spatial and temporal orientation of the currents of the main and additional windings of the stator and rotor phases of the compensated asynchronous motor. Achieving this goal is based on establishing the regularities of the influence of the value of the compensating capacitance on the energy characteristics of a compensated asynchronous motor during its start-up and reaching the nominal electromagnetic moment on the rotor shaft. Numerical modelling is performed at the 30o spatial shift angle of the phase axes of the main and additional phase windings of the stator of a compensated asynchronous motor. This ensures that the currents of the main and additional windings of the CAM stator are equal. As the numerical experiment showed, changing the value of the compensation capacitance gives an idea of the conditions for ensuring the normal excitation mode of such an electric device. Ensuring normal excitation during the start-up of a compensated asynchronous motor leads to changes in the energy parameters of the machine – minimising power losses in the windings and reactive power consumption by the motor and increasing its power factor. It is established that the value of the compensation capacitance required to ensure the normal excitation mode during start-up and the steadystate normal mode of a compensated asynchronous motor differ. As a result of modelling, it was found that in order to ensure an energy-efficient starting mode and acceleration to the nominal slip, the value of the compensating capacity of an asynchronous motor should be almost 5 times greater than for a steady-state nominal mode. The results of these studies can be useful for improving the energy efficiency of micro power grids that operate small-and medium-power asynchronous motors

Keywords

• energy efficiency
• medium-power motors
• reactive power
• internal capacitive compensation
• compensating capacity
• starting mode