Design and Implementation of Switched Capacitor Banks Controlled by a Programmable Logic Controller for Power Factor Improvement of Three-Phase Induction Motors

Abstract

Industries widely use three-phase inductive loads, such as induction motors, due to their cost-effectiveness, low maintenance, reliability, and durability. However, these loads decrease the power factor, which leads to power wastage, higher billing costs, and penalties from electric power supply companies. To address this issue, a system has been developed that employs a programmable logic controller (PLC) to enhance the power factor of three-phase loads, which reduces the plant's operating costs and lessens the demand for electricity supply from the utility side. The system combines hardware and software components. The software includes logic-based PLC programming that controls the sequence of operations step by step, whereas hardware consists of power and control circuits and protective devices. When an inductive load is added to the system, the PLC reads the input signal from the magnetic contactor's contactor coil connected with the motor and sends an output signal to the corresponding contactor coil of the magnetic contactor to switch the appropriate capacitor bank to enhance the power factor. This paper discusses the experimental results for seven cases utilizing different load combinations with and without the developed system. Thus, energy management requires improving the load's power factor, and the PLC is used as a power factor controller (PFC) for many industrial control applications.