Implementation of Automatic Excitation Initiator Circuit using Microcontroller based PLC for Standalone Induction Generator

摘要

As per observation most of single phase or multiphase standalone induction generators are unable to self-excite. The no-load terminal voltage of low power Standalone single phase induction generators at rated speed is in the range of 2 to 5 volts RMS in unexcited mode due to low residual magnetic field of machine core. The residual magnetic field in the core of such machines does not remain enough at turn off so that the machine can self-excite at next starting of machine. The capacitors connected across main winding of single phase induction machine do not support self- excitation process because capacitors fully discharge across the winding resistance of machine. Generally pre charged capacitors are connected across the machine while rotating the shaft of machine to excite the machine and to achieve rated terminal voltage. This process is manual and needs a personal effort to establish excitation process. The process of excitation can be automated with the help of an electronic circuitry to omit the personal efforts and to make the machine operation fast. In this paper an electronic circuitry based on programmable logic controller is elaborated which automates the process of automation of machine excitation. This paper also covers circuitry of OPAMP based voltage sensor which sends terminal voltage signal of induction generator to Programmable Logic Controller to take appropriate switching action to push induction machine into self-excited state.