Design Of A 4Th Quadrat Chopper For Dc-Dc Motor

ABSTRACT

cThe chopper responds by providing variable voltage to the armature for receiving desired speed in accordance with the signal received from controller via firing circuit. There are two controlling loops one for controlling current and one for controlling speed. In this way modeling of separately excited DC motor is done. The model is simulated using matlab after obtaining the complete model of the system. Simulation is done for analyzing various speeds and load torque conditions. The above simulated model can be implemented as applicable to be used in HEV’S in open loop working in the entire four quadrants as per voltage v/s current plot. The IGBT’S are triggered by using pulse width modulation technique .Recent HEV employs a complex control system that involves vehicle to work on electric motor till the speed switch over the control of vehicle of the IC engine .The speed limit depends upon the efficiency of the IC engines in its initial gears .Therefore in the above context, the four quadrant operation is designed to operate at speeds from 0 to 700rpm.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1      BACKGROUND OF THE STUDY

• AIM/OBJECTIVE OF THE STUDY
• PURPOSE OF THE STUDY
• SCOPE OF THE STUDY
• LIMITATION OF THE STUDY
• SIGNIFICANCE OF THE STUDY
• APPLICATION OF THE STUDY
• RESEARCH METHODOLOGY
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

• OVERVIEW OF DC MOTOR
• REVIEW OF DIFFERENT TYPES DC MOTOR
• PRINCIPLE OF DC MOTOR
• DESCRIPTION OF CHOPPER
• PRINCIPLE OF CHOPPER OPERATION

CHAPTER THREE

METHODOLOGY

• BASICS OF CHOPPER
• SYSTEM MODELLING
• SIMULATION

CHAPTER FOUR

RESULT ANALYSIS

• RESULTS

CHAPTER FIVE

• CONCLUSION AND RECOMMENDATION
• FUTURE SCOPE
• REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

The application of DC-DC convertors are widely found in switched mode power supplies. Input of the converter varies widely especially when the source is renewable source .So the input to these converters is unregulated but the output from this is expected to be harmonic and ripple free. Voltage regulation in the DC-DC converters is achieve by continuous adjustment of the amount of energy absorbed from source that is injected in the load which in turn can be achieved by controlling the time intervals of energy absorption and injection in the circuits . These two basic process of absorption and injection constitutes a switching cycle presented as duty cycle of operation D. There are two modes of operation current continuous and current discontinuous mode.

Various techniques were applied aiming at regulating chopper’s duty cycle ‘d’ for reducing voltage ripple’s and to maintain voltage at minimum switching losses. PWM converters are required to operate at high frequency due to demand high power density with reduced switching losses by using soft switching techniques. In order to achieve this aim zero-voltage switching method is employed in the main circuit with an auxiliary circuit that is activated just before the main circuit is to be turned on and is deactivated after sometime. Auxiliary circuit consist of IGBT((active switch) and passive elements (inductances and capacitances) that have lower ratings than the main circuit as auxiliary circuit is only activated for the fraction of switching cycle. PWM with such circuits are referred as zero-voltage transitions .The auxiliary circuits can be a non-resonant circuit with hard turn off or resonant circuit with soft turnoff.

1.2                                 AIM AND OBJECTIVE OF THE STUDY

The main aim of this work is to setup a device that will control the speed of separately excited DC motor using chopper. The objectives are:

1. To provide a variable voltage to the armature.
2. To control the speed of a dc motor from 0 to rated speed

• To simulate a model using MATLAB

1. To analyze various speeds and load torque conditions of a dc motor.

1.3                                            PURPOSE OF THE STUDY

The purpose of the study is to ensure that a dc motor operates from the zero speed to the rated speed. This can be done by using choppers from 0 to rated speed.

1.4                                                SCOPE OF THE STUDY

The major component of this work is the chopper. The chopper responds by providing variable voltage to the armature for receiving desired speed in accordance with the signal received from controller via firing circuit. There are two controlling loops one for controlling current and one for controlling speed. In this way modeling of separately excited DC motor is done.

1.5                                           LIMITATION OF THE PROJECT

Using chopper to control the speed of a dc motor has the following limitations:

1. Source current of a chopper fed drive consists of pulses which are rich in harmonics and can also cause fluctuations in supply voltage.
2. For the same rating the size of DC drive is much bigger than the AC drives.

• DC drives require more maintenance.

1.6                                         SIGNIFICACE OF THE STUDY

Chopper circuit is simple and can be modified to provide regeneration and the control is also simple.  Lower cost, reliability and simple control for variable speed application. And it generates the maximum speed of a dc motor, that is, from 0 to the rated speed.

1.7                                        APPLICATION OF THE STUDY

Chopper speed control of the dc motor can be useful in the following places:

1. Battery operated vehicle.
2. Traction motor control in electric traction.

• Trolley Cars

2. Electric braking

1.8                                             RESEARCH METHODOLOGY

In the course of carrying this study, numerous sources were used which most of them are by visiting libraries, consulting journal and news papers and online research which Google was the major source that was used.

1.9                                    PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work,   chapter two presents the literature review of the study,  chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.