PLC Based Monitoring & Protection of 3-Phase Induction Motors against Various Abnormal Conditions

In this manuscript, low-cost and efficient protection scheme for three phase induction motors is designed against the most commonly occurring abnormal conditions – over current, over voltage and over temperature. This protection scheme makes use of the modern control equipments used in the industrial processes. The brain of the scheme – Programmable Logic Controller (PLC) – continuously monitors the different parameters of an induction motor and gives an alert message on Human Machine Interface (HMI) about any abnormal condition detected, and trips the induction motor if no troubleshooting action is taken within defined time. The design has an additional feature of automatically start of induction motor when fault is removed which mitigates the need of a recloser. The design has been tested on different three phase induction motors of different parameters available in laboratory. Keeping operating time in consideration the design replaces the old mechanical relays with modern solid-state relays, and the same relay has been used for signaling for all abnormal conditions which again makes this design an economically low-cost.