International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 02 | Feb -2017
p-ISSN: 2395-0072
www.irjet.net
PLC APPLICATIONS FOR SPEED CONTROL OF INDUCTION MOTOR THROUGH VFD Ms. N. M. Rao1, Vidya Gaikwad2, Prachi Kashid3 , Pavan Dandale4 1Assistant
professor, Electrical Dept, AISSMS’S IOIT, Pune, India. year student, Electrical Dept, AISSMS’S IOIT, Pune, India. 34th year student, Electrical Dept, AISSMS’S IOIT, Pune, India. 44th year student, Electrical Dept, AISSMS’S IOIT, Pune, India. 24th
---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - The paper is about controlling the speed of a
three phase induction motor using variable frequency drive(VFD) through programmable logic controller(PLC). Programmable logic controller is an industrial controlling device and is used to automate machines and factory assembly lines. Main purpose of this paper is to automate the three phase induction motor by controlling the inputs to variable frequency drive through PLC and therefore as a result the inputs to the induction motor will be changed and thus the speed of induction motor will changed accordingly. VFD employed in this experiment is based on V/f method of speed control in which flux remain constant. Key Words: Variable frequency drive, Programmable logic controller, Induction motor, V/f method.
1.INTRODUCTION
|
Stator frequency control method used have disadvantages such as at low frequencies reactance will be low leading to high motor currents, more losses and reduces efficiency, after saturation of magnetic circuit, motor parameters will changes leading to inaccurate speed-torque characteristics.[2]
All the above mentioned methods of speed control have considerable disadvantages therefore V/f method of speed control is adopted which has advantages such as starting current decreases, however starting torque becomes more.
A variable frequency drive is used for applications where speed control is important factor due to load changes wherein the speed needs to be increased or decreased accordingly. VFD reduces energy consumption and energy costs, extents equipment life and reduces maintenance cost.
Figure 1: Block diagram of variable frequency drive 1.2 Programmable logic controller It is used in electrical system to improve the reliability and efficiency of electrical equipment (electrical motor) inn automation processes. In this application PLC of Allen Bradley is used which communicate with VFD and in turn control the speed of induction motor. Main parts of PLC are
Stator voltage control method used have many disadvantages such as it offers control over limited range, its use introduces harmonics content and thus reduces the input supply power factor and can be used for only low power drives like fan, blowers etc.[2]
© 2017, IRJET
Stator current control method used have disadvantages such as low starting torque as compared to stator voltage control method.
1.1 Variable frequency drive
Three phase induction motors are mostly used AC motors in industry for various operations due to its low cost and simplicity. Many factories use PLCs in automation processes to diminish production cost and to increase quality and reliability. By implementing a monitoring and control system for the speed of motor, the induction motor can be used in high performance variable speed application. Variable frequency drives are generally required because in many applications it is not desired to run the motor at same speed all the time due to surrounding circumstances. For example, a pump delivering cooling liquid supply may require peal load operation only for a requisite period of time and may require only much less amount during remaining time of day. VFD will allow the speed of the pump to run at a lower rate in such case thereby enabling energy saving benefits [1]. Speed control methods of induction motors
Impact Factor value: 5.181
|
ISO 9001:2008 Certified Journal
|
Page 1221