PLC BASED INDUCTION MOTOR STARTING AND PROTECTION (original) (raw)

— The intent of the paper is starting, speed control and protection of induction motor. There bylimitingthe starting current and increase the starting torque and so as to protect the induction motor. There are different methods for starting of the Slip Ring induction Motor. But we have opted the Rotor Resistance Control method forStarting the Induction Motor. Programming is done by using Programmable Logic Controller; control panel isdesigned and programmed according to requirements. The motor will start with high rotor resistance and the rotorresistance is cut off with respective time delay and the motor will run at rated speed. The contactor is used for theswitching of three phase supply to the stator winding. This is how the starting, speed control and protection of induction motor is achieved and the operation is very reliable, sufficiently high efficient. Induction motors arewidely used in many operating areas and industrial applications as they are simple, robust, reliable and have lowproduction costs. The reliability of an induction motor is of great Importance in applications such as commercial,aerospace and military and many industrial applications. In this paper different problems of IM are dealt with asover current, overvoltage, over temperature, over speed, inrush current, vibration monitoring during it's time ofoperation. There are various proposed methods for fault diagnosis and protection of IM. Some of them are Stator fault monitoring techniques, protection system using On-line fault detection, Programmable Logic Controller (PLC)based protection system. In this study, the method which is applied is PLC based protection system of an IM. INTRODUCTION The starting, speed control and protection of Induction motor can achieved easily by using PLC.Three-phase induction motors are widely used in industrial drives because they are rugged, reliable and economical. High Starting torque is a desired feature in some special industrial applications which use 3-Ph Slip Ring Induction motor. An induction motor or asynchronous motor is a 3phase 4pole induction motor. This is a type of alternating current motor where power is supplied to the rotor by means of electromagnetic induction. The 3 phase 4pole induction motor electric motor turns because of magnetic force is exert between the stationary electromagnet called the stator and a rotating. The three-phase induction motors are the most widely used electric motors in industry. They run at essentially constant speed from no-load to full-load .However ,the speed is frequency dependent and consequently these motors are not easily adapted to speed control .We usually prefer d.c. motors when large speed variations are required. Nevertheless, the 3-phase induction motors are simple, rugged, low-priced, easy to maintain and can be manufactured with characteristics to suit most industrial requirements.This3phase 4pole inductions electric motor turns because of magnetic force exert between emotion less electromagnet called the stator and a rotating electromagnet called the rotor. If the slip ring induction motor is started with all the slip rings or the rotor terminals shorted, like a normal induction motor, then it suffers extremely high locked rotor current, ranging upto1400%, accompanied with very low locked rotor torque as low as 60%.So,it is not advised to start a slip ring induction motor with its