Comparative Analysis On The Effect Of Different Methods Of Starting Three Phase Squirrel Cage Induction Motor

Electrical Electronics Engineering | Industrial Physics | Physics

The initiation of a three-phase squirrel cage induction motor employs various methods, each impacting its performance and efficiency differently. Direct online (DOL) starting, a conventional method, involves supplying full voltage to the motor windings, leading to high inrush current and mechanical stress. Soft starters gradually ramp up the voltage, reducing initial current surges and minimizing mechanical shock, enhancing motor longevity and reliability. Conversely, star-delta starters first connect the motor in a star configuration, reducing voltage and current during startup before switching to a delta configuration, which limits torque and current surges. Additionally, variable frequency drives (VFDs) offer precise control over motor speed and torque by adjusting the frequency and voltage of the supplied power, enhancing energy efficiency and allowing for smoother acceleration. Each starting method presents distinct advantages and disadvantages, influencing factors such as motor lifespan, power quality, and operational cost, thus necessitating careful consideration of specific application requirements to optimize motor performance and longevity.

Induction Motor is the most widely used motor due to this reliability robust and low cost and it is used in both household. An industrial application is due to their high torque to volume ratio, ruggedness and low maintenance. Induction Motor draws a high starting current during starting period which effects on electromagnetic torque, speed and current. Traditional method include DOL, auto transformer, star delta starter etc. control this parameter up to certain limits. This study is about the starting method of induction motor DOL starter, star delta, autotransformer starter. Analysis is made for speed, torque and current during start. Simulation is made in MATLAB and comparatively results are estimated.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

1.0 INTRODUCTION

1.1 BACKGROUND OF THE STUDY

PROBLEM STATEMENT
AIM AND OBJECTIVES OF THE STUDY
SIGNIFICANCE OF THE STUDY
SCOPE OF THE STUDY
LIMITATION OF THE STUDY
RESEARCH METHODOLOGY
PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

INTRODUCTION
OVERVIEW OF STARTER
REVIEW OF RELATED LITERATURE
COMPARATIVE ANALYSES REVIEW
HISTORICAL BACKGROUND OF AN AC INDUCTION MOTOR

CHAPTER THREE

3.0 METHODOLOGY

ANALYSIS OF DIFFERENT STARTING METHOD
- DIRECT-ON-LINE STARTING OF INDUCTION MOTOR
- STAR-DELTA STARING OF INDUCION MOTOR
- AUTO-TRANSFORMER STARTING OF INDUCTION MOTOR

3.2 COMPARISON OF OUTPUT WAVEFORM OF STARTING PARAMETERS

CHAPTER FOUR

4.0 RESULTS AND DISCUSSION

RESIULT
DISCUSSION

CHAPTER FIVE

CONCLUSION
REFERENCES

CHAPTER ONE

1.0 INTRODUCTION

1.1 BACKGROUND OF THE STUDY

Starting induction motors on isolated or weak systems is a highly dynamic process that can cause motor and load damage as well as electrical network fluctuations. Mechanical damage is associated with the high starting current drawn by a ramping induction motor. In order to compensate the load increase, the voltage of the electrical system decreases. Different starting methods can be applied to the electrical system to reduce these and other starting method issues.

A 3-phase induction motor is theoretically self-starting. The stator of an induction motor consists of 3-phase windings, which when connected to a 3-phase supply creates a rotating magnetic field. This will link and cut the rotor conductors which in turn will induce a current in the rotor conductors and create a rotor magnetic field. The magnetic field created by the rotor will interact with the rotating magnetic field in the stator and produce rotation. Based on the construction of the rotor, a 3-phase induction motor can be categorized into two types:

Squirrel Cage Induction Motor
Wound Rotor or Slip Ring Induction Motor

The stator of both types of motors consists of a three phase balanced distributed winding with each phase mechanically separated in space by 120 degrees from the other two phase windings. This gives rise to a rotating magnetic field when current flows through the stator.

In squirrel cage IM, the rotor consists of longitudinal conductor bars which are shorted at ends by circular conducting rings. Whereas, the wound rotor IM has a 3-phase balanced distributed winding even on the rotor side with as many number of poles as in the stator winding.

Squirrel cage induction motor just before starting is similar to a poly phase transformer with a short-circuited secondary. If normal voltage is applied to the stationary motor then, as in the case of a transformer, a initial current, to the turn of 5 to 6 times the normal current or the normal rated current, will be drawn by the motor from the mains. This initial excessive current is objectionable, because it will produce line voltage (The potential difference or the voltage across two phases) drop, which in turn will affect the operation of the other electrical equipment and the lights connected to the same line.

The initial rush of current is controlled by applying a reduced voltage to the stator (motor) winding during the starting period and then the full normal voltage is applied when the motor has run up to speed. For the small capacity motors say up to 3H.P, full normal voltage can be applied at the start. However to start and stop the motor and to protect the winding from the over load current and low voltages, a starter is required in the motor circuit. In addition to this the starter may also reduce the applied voltage to the motor at the time of starting. A 3-phase induction motors employ a starting method not to provide a starting torque at the rotor, but because of the following reasons:

Reduce heavy starting currents and prevent motor from
Provide overload and no-voltage protection starter.

1.2 PROBLEM STATEMENT

Induction motor starting is a highly dynamic process that can have many adverse effects on the entire power system. Two of the prominent issues are the effects caused by high inrush currents on the mechanical system of the load, and the response of the generation source to the load step, of which voltage dip is of most concern. To address these issues, different starting methodologies have been developed to mitigate damaging effects. It is not economically practical to test each of these methods on a physical system because of possible equipment damage, electrical system vulnerability, and other problems. Through simulation of these systems it possible to compare the various starting methods in an economical, secure and yet effective manner.

1.3 AIM AND OBJECTIVES OF THE STUDY

The main aim of this study is to compare different types of motor starter according to their simulation models. The objectives of this work are as follows:

To study the starting period of induction motor when it’s connected with different starter at the time of starting.
To analysis starting current, torque and speed of induction motor when it is started with the help of direct-on-line, star-delta and auto-transformer

Using MATLAB SIMULINK we are going to compare their output

1.4 SIGNIFICANCE OF THE STUDY

This study will help to understand the starting period and their effect on induction motor. By building an accurate and usable simulation models this work is can aid the designer in making the choice of an appropriate motor starting method.

1.5 SCOPE OF THE STUDY

The purpose of this work is to develop an accurate simulation for comparing starting methods of a squirrel cage induction motor system. This work is to provide a comprehensive approach to simulate the starting methods and dynamic machine models for this type of system. The simulation program is performed in Matlab/Simulink as it has become a widely used and accepted platform. Matlab/Simulink allows for easily testing different simulation step times and solution algorithms (TransÉnergie Technologies Inc., 2003).

1.6 LIMITATION OF THE STUDY

As we all know that no human effort to achieve a set of goals goes without difficulties, certain constraints were encountered in the course of carrying out this project and they are as follows:-

Difficulty in information collection: I found it too difficult in laying hands of useful information regarding this work and this course me to visit different libraries and internet for solution.
Difficulty in parts gathering: I found it too difficult when setting up the simulation equipment because of the unfamiliarity of the equipment used.

1.7 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.

1.8 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.