Abstract
The study is devoted to energy efficiency control of squirrel-cage induction motors of low and medium power and is a continuation of development of the theory of compensated induction motors. The aim of the research is to substantiate the influence of capacitance value on compensation of internal capacitive reactive power of induction motor in starting mode. The mathematical modeling of compensated induction motor allowed us to study quasitransient electromagnetic processes taking into account spatial and temporal directionality of currents of main and additional windings of stator and rotor phases of compensated induction motor. Achievement of the objective is based on the establishment of regularities of influence of compensating capacitance value on energy characteristics of a compensated induction motor during its start-up and achievement of nominal electromagnetic torque on the rotor shaft. Numerical modeling is performed at spatial displacement of phase axes of main and additional phase windings of stator of compensated induction motor by 30°. It provides equality of currents of main and auxiliary stator windings of CAM. As shown by numerical experiment, changing the value of compensation capacitance gives an idea of the conditions for ensuring normal excitation mode of such electrical device. Provision of normal excitation at start-up of a compensated induction motor leads to changes in energy parameters of the machine - minimization of power losses in windings and reactive power consumed by the motor and increase of its power factor. It has been established that the value of compensation capacitance required to ensure normal excitation mode at start-up and steady-state normal mode of a compensated induction motor is different. As a result of simulation, it was found that to ensure energy-efficient starting mode and acceleration to nominal slip, the value of compensating capacity of induction motor should be almost 5 times greater than for the steady-state nominal mode. The results of these studies can be useful for improving the energy efficiency of microgrids with small and medium capacity induction motors.