International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 07 Issue: 10 | Oct 2020 www.irjet.net p-ISSN: 2395-0072 © 2020, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 879 IMPLEMENTATION OF OVERVOLTAGE PROTECTION SCHEME FOR INDUCTION MOTOR Chandan Pathak 1 , Dr. M.K. Bhaskar 2 , Nitish Roat 3 , Rakesh Kumar 4 , Prachi Bundela 5 , Monika Meena 6 2 Professor, Dept. of Electrical Engineering, MBM Engineering College, Jodhpur, Rajasthan, India 1,3,4,5,6 Students of B.E. Electrical Engineering, MBM Engineering College, Jodhpur Rajasthan, India ---------------------------------------------------------------------***---------------------------------------------------------------------- Abstract – Induction motors are widely used nowadays with applications ranging from residential, commercial and industrial like washing machines, blenders, drilling machines, pumps, compressors, paper mills, textile mills etc. It could be assumed that properly planned, dimensioned, designed, installed, operated and maintained motor systems and drives should not break down, in reality however these conditions are hardly ever ideal. Motor breakdowns can be attributed due to motor undervoltage, overvoltage and electrical faults. These breakdowns in motor operations result in huge losses both in time and money. Hence it becomes necessary to select proper protection systems to prevent damage to motors, so as to preserve the lifetime of motors, ensuring operation continuity, preventing motors from stopping abruptly and enabling restart in the best conditions. This project is designed to detect overvoltage conditions, so that under these conditions damage to motors can be prevented. Key Words: Astable multivibrator, Decade counter, Overvoltage, Time delay, Comparators, 555 Timer, Relay, Induction motor. 1. INTRODUCTION The operators of electrical drive systems are under continual pressure to reduce maintenance costs and prevent unscheduled down times, which result in lost production and financial income. Most of the surveys of failure in electrical rotating machines indicate that in general, failures are dominated by bearing and stator winding failures with rotor winding problems being less frequent. Thus motor protection is an essential function for ensuring the continuity of machine operation. So, overvoltage protectors are the arrangements implemented in order to avoid operation of motors in abnormal conditions which could result in negative events such as: overheating, premature ageing, destruction of electrical windings, damage to coupling or gear box. This project helps us to detect overvoltage conditions by continuously comparing the DC sampled voltage which we get at the output of diode D1 with the reference voltage set by potentiometer VR3 and in case of overvoltage conditions the output of the comparator A3 is high, after this with the help of integrator network, Zener diode, SCR and transistors we are able to de-energize the relay thus disconnecting the load from the supply mains. We have used ICs to perform the overvoltage protection instead of circuit breakers or microcontroller. In case of overvoltage condition we prevent the connection of the motor or disconnection of the motor, as an increased voltage could not ensure a correct operation of the motor. 2. OVERVOLTAGE PROTECTION SCHEME FOR INDUCTION MOTOR The overvoltage protection of induction motor works by comparing DC sampled voltage with the reference voltage, so if overvoltage condition occurs the DC sampled voltage is more than the reference voltage, so further operations are performed by the circuit in order to de-energize the relay thus disconnecting load from mains supply. The main components of the overvoltage protection are NE555 timer, decade counter 4017, quad comparator LM339, quad NOR gate CD4001, current transformer, relay, transistors BC547 and SL100 and a few other components. In normal operating conditions while switching on the mains supply and the 12V DC supply, NOR gate N2 of CD 4001 IC is wired as a NOT (inverter) gate for making an initial reset pulse circuit with RC network formed by R12 and C6. This reset circuit is essential to reset decade counter CD 4017 on initial power on, so that output Q0 of decade counter becomes high and switches on T2. This in turn energizes relay RL1 to provide AC power to the load. In order to achieve overvoltage protection for induction motor, the amount of load current to the motorized electrical gadget is sensed by the coil of 50 Hz, 5A current transformer in the form of AC voltage. Sampled AC voltage in CT coil is proportional to the load current of the electrical gadget. This 50 Hz AC voltage across the coil is rectified and filtered to get corresponding DC sample voltage which is compared with the VR3 reference voltage. If overvoltage condition occurs then this output is high which is further applied to reverse-biased Zener diode through an integrator network to provide the required time delay, then SCR is fired, when the anode potential of the SCR decreases it turns off transistor T4, due to which transistor T3 turns on which decreases the bias of transistor T2 due to which the relay is de-energised and thus the load gets disconnected from the mains supply and hence the damages to the induction motor has been prevented.