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V/f CONTROL OF INDUCTION MOTOR DRIVE

I V/f CONTROL OF INDUCTION MOTOR DRIVE A Thesis submitted in partial fulfillment of the requirements for the degree of Bachelor of Technology in Electrical Engineering By Devraj Jee (109EE0039) Nikhar Patel (109EE0087) Under the guidance of Prof. M. Pattnaik Department of Electrical Engineering National Institute of Technology Rourkela-769008 (ODISHA) May-2013 ii DEPARTMENT OF ELECTRICAL ENGINEERING NATIONAL INSTITUTE OF TECHNOLOGY, ROURKELA ODISHA, INDIA-769008 CERTIFICATE This is to certify that the thesis entitled V/f CONTROL of INDUCTION MOTOR DRIVE , submitted by Mr. Devraj Jee (Roll No.)

In 1896, General Electric and Westinghouse signed a cross-licensing agreement for the Squirrel-Cage design of the Induction Motor, and by 1900, it was all set to become the industrial staple. By 1910, locomotives in Europe were fitted with Induction Motors and were able …

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  Control, Drive, Motor, Induction, Cage, Squirrel, F control of induction motor drive

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Transcription of V/f CONTROL OF INDUCTION MOTOR DRIVE

1 I V/f CONTROL OF INDUCTION MOTOR DRIVE A Thesis submitted in partial fulfillment of the requirements for the degree of Bachelor of Technology in Electrical Engineering By Devraj Jee (109EE0039) Nikhar Patel (109EE0087) Under the guidance of Prof. M. Pattnaik Department of Electrical Engineering National Institute of Technology Rourkela-769008 (ODISHA) May-2013 ii DEPARTMENT OF ELECTRICAL ENGINEERING NATIONAL INSTITUTE OF TECHNOLOGY, ROURKELA ODISHA, INDIA-769008 CERTIFICATE This is to certify that the thesis entitled V/f CONTROL of INDUCTION MOTOR DRIVE , submitted by Mr. Devraj Jee (Roll No.)

2 109EE0039), and Mr. Nikhar Patel (Roll No. 109EE0087) in partial fulfilment of the requirements for the award of Bachelor of Technology in Electrical Engineering during session 2012-2013 at National Institute of Technology, Rourkela is a bona-fide record of research work carried out by them under my supervision and guidance. The candidates have fulfilled all the prescribed requirements. The Thesis which is based on candidates own work, have not submitted elsewhere for a degree/diploma. In my opinion, the thesis is of standard required for the award of Bachelor of Technology degree in Electrical Engineering. Place: Rourkela Dept.

3 Of Electrical Engineering Prof. M. Pattnaik National institute of Technology Supervisor Rourkela-769008iii ACKNOWLEDGEMENTS We would like to thank our project supervisor, Prof. M. Pattnaik, for her constant motivation and guidance during the project. We extend our heartfelt gratitude to Prof. B. Chittibabu for his unparalleled and timely help and support. This project could never have been completed without him. We would also like to thank all our sources, mentioned in the references, and our friends who helped us by providing mental and logistical support. Last but not the least we would like to thank our parents and God Almighty. Devraj Jee Nikhar Patel (Electrical Engineering) National Institute of Technology, Rourkela iv Dedicated to The Department of Electrical Engineering, NIT Rourkela, for all the knowledge and wisdom imparted to us in our four years and for preparing us for our lives ahead.

4 V ABSTRACT This thesis presents the need of Speed CONTROL in INDUCTION Motors. Out of the various methods of controlling INDUCTION motors, V/f CONTROL has proven to be the most versatile. The overall scheme of implementing V/f CONTROL has been presented. One of the basic requirements of this scheme is the PWM Inverter. In this, PWM Inverters have been modeled and their outputs fed to the INDUCTION MOTOR drives. The uncontrolled transient and steady state response of the INDUCTION MOTOR has been obtained and analyzed. A MATLAB code was developed to successfully implement Open Loop V/f CONTROL on a PWM-Inverter fed 3-phase INDUCTION MOTOR , and the Torque was found to be constant for various rotor speeds.

5 This was followed by a MATLAB model for Closed-Loop V/f CONTROL on a PWM-Inverter fed 3-phase INDUCTION MOTOR . It was observed that using a Closed-Loop scheme with a Proportional Controller gave a very superior way of controlling the speed of an INDUCTION MOTOR while maintaining a constant maximum torque. vi Contents: Certificate ii Acknowledgements iii Abstract v Contents vi List of Figure viii Abbreviations and Acronyms ix Chapter 1 INTRODUCTION Motivation 2 INDUCTION Motors: A Brief History 3 V/f CONTROL of INDUCTION MOTOR : An Introduction 4 Objective of the Project 5 Scope of the Thesis 5 Organization of the Thesis 5 Chapter 2 INDUCTION MOTOR DRIVES Introduction 7 Construction 7 Working 7 Torque-Speed Analysis 8 vii Chapter 3 PWM INVERTER Introduction 12 Single-Phase PWM Inverter 12 Three-Phase PWM Inverter 15 Chapter 4 V/f CONTROL OF INDUCTION MOTOR Introduction 23 Uncontrolled PWM Inverter-fed INDUCTION MOTOR 24 Open-loop V/f CONTROL Using MATLAB 32 Closed-loop V/f CONTROL of INDUCTION MOTOR Using MATLAB 33 Chapter 5 CONCLUSIONS Conclusions 37

6 References 38 viii LIST OF FIGURES Sl. No. Name of Figure Page No. 1 Equivalent Circuit of an INDUCTION MOTOR 8 2 Torque and Speed Curves for an INDUCTION MOTOR 9 3 Simulink Model for 1-Phase Inverter with Resistive Load 13 4 Input and Output Voltage for Single-Phase PWM Inverter 15 5 Simulink Model for 3-Phase PWM Inverter 16 6 Output and Input Current Waveforms for 3-phase PWM Inverter 17 7 3-phase PWM Inverter Using Simulink Blocks 19 8 Input and Output Voltage Waveforms for 3-phase PWM Inverter With Inductive Load 20 9 Torque-Speed Characteristics for V/f Controlled INDUCTION MOTOR 23 10 3-Phase INDUCTION MOTOR fed by PWM Inverter 24 11 Parameters passed for PWM Generator Block 25 12

7 Parameters passed for Universal Bridge Block 26 13 Parameters passed for Asynchronous Machine Block 27 14 Torque Characteristics for Uncontrolled INDUCTION MOTOR 28 15 Speed Characteristics for Uncontrolled INDUCTION MOTOR 29 16 Rotor Current Characteristics for Uncontrolled INDUCTION MOTOR 30 17 Stator Current Characteristics for Uncontrolled INDUCTION MOTOR 31 18 Torque vs Speed Curves for Open-loop V/f Controlled INDUCTION MOTOR for Various Frequencies 33 19 Torque-Speed Characteristics for Tlstarting= and Wref= 1000 rpm in Closed-loop V/f CONTROL of INDUCTION MOTOR 34 20 Torque-Speed Characteristics for Tlstarting = 1 and Wref= 500 rpm in Closed-loop V/f CONTROL of INDUCTION MOTOR 35 ix ABBREVIATIONS AND ACRONYMS DC - Direct Current AC - Alternating Current IGBT - Insulated-Gate Bipolar Transistor PWM - Pulse Width Modulation RPM - Rotations Per Minute - Tlstarting - Starting Load Torque Wref - Reference Speed x CHAPTER1 Introduction2 Motivation Electrical Energy already constitutes more than 30 % of all energy usage on Earth.

8 And this is set to rise in the coming years. Its massive popularity has been caused by its efficiency of use, ease of transportation, ease of generation, and environment-friendliness. Part of the total electrical energy production is sued to produce heat, light, in electrolysis, arc-furnaces, domestic heating etc. Another large part of the electrical energy production is used to be converted into mechanical energy via different kinds of electric motors- DC Motors, Synchronous Motors and INDUCTION Motors. INDUCTION Motors are often termed the Workhorse of the Industry . This is because it is one of the most widely used motors in the world.

9 It is used in transportation and industries, and also in household appliances, and laboratories. The major reasons behind the popularity of the INDUCTION Motors are: i. INDUCTION Motors are cheap compared to DC and Synchronous Motors. In this age of competition, this is a prime requirement for any machine. Due to its economy of procurement, installation and use, the INDUCTION MOTOR is usually the first choice for an operation. ii. squirrel - cage INDUCTION Motors are very rugged in construction. There robustness enables them to be used in all kinds of environments and for long durations of time. iii. INDUCTION Motors have high efficiency of energy conversion.

10 Also they are very reliable. iv. Owing to their simplicity of construction, INDUCTION Motors have very low maintenance costs. v. INDUCTION Motors have very high starting torque. This property is useful in applications where the load is applied before starting the MOTOR . Another major advantage of the INDUCTION MOTOR over other motors is the ease with which its speed can be controlled. Different applications require different optimum speeds for the MOTOR to run at. Speed CONTROL is a necessity in INDUCTION Motors because of the following factors: i. It ensures smooth operation. ii. It provides torque CONTROL and acceleration CONTROL . 3 iii. Different processes require the MOTOR to run at different speeds.


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