Research on Power Factor Compensation and Self-excitation Phenomenon of Induction Motors

Low-voltage induction motors, which are widely used in industrial fields, have a large change in power factor from starting to reaching the rated speed when starting directly, and are used by installing an additional power factor compensation capacitor due to the low power factor at the rated speed. However, depending on the additional installation of this capacitor and the operating conditions of the induction motor, a self-excitation phenomenon in which the capacitor leading current becomes larger than the induction motor magnetizing current may occur, so detailed analysis and research on reduction measures are necessary. In this paper, the changes of parameters related to self-excitation during the starting in an analytical model including a 50 [hp] induction motor and a power factor correction capacitor is quantitatively analyzed using by electromagnetic transients program. In order to reduce the self-excitation phenomenon, the proper connection timing of capacitor was suggested based on the analysis results, and a method of implementing the capacitor switching controller was presented. In the analysis model to which this was applied, the application and feasibility of the switching controller is verified by the analysis and comparison of the magnetization current of the induction motor and the current of the capacitor.