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TITLE PAGE

 

BY

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--/H2013/01430
DEPARTMENT OF ----
SCHOOL OF ---
INSTITUTE OF ---

DECEMBER,2018

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APPROVAL PAGE

This is to certify that the research work, "design and construction of forward and reverse direct online motor starter" by ---, Reg. No. --/H2007/01430 submitted in partial fulfillment of the requirement award of a Higher National Diploma on --- has been approved.

By
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Supervisor                                                  Head of Department.
Signature……………….                           Signature……………….        

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External Invigilator

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DEDICATION
This project is dedicated to Almighty God for his protection, kindness, strength over my life throughout the period and also to my --- for his financial support and moral care towards me.Also to my mentor --- for her academic advice she often gives to me. May Almighty God shield them from the peril of this world and bless their entire endeavour Amen.

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ACKNOWLEDGEMENT

The successful completion of this project work could not have been a reality without the encouragement of my --- and other people. My immensely appreciation goes to my humble and able supervisor mr. --- for his kindness in supervising this project.
My warmest gratitude goes to my parents for their moral, spiritual and financial support throughout my study in this institution.
My appreciation goes to some of my lecturers among whom are Mr. ---, and Dr. ---. I also recognize the support of some of the staff of --- among whom are: The General Manager, Deputy General manager, the internal Auditor Mr. --- and the ---. Finally, my appreciation goes to my elder sister ---, my lovely friends mercy ---, ---, --- and many others who were quite helpful.

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A direct on line starter, often abbreviated DOL starter is an electrical/electronic circuit composed of electro-mechanical and electronic devices which are employed to start and stop an electric motor. Regardless of the motor type (AC or DC), the types of starters differ depending on the method of starting the motor. A DOL starter connects the motor terminals directly to the power supply. Hence, the motor is subjected to the full voltage of the power supply. Consequently, high starting current flows through the motor. Electric motors can run in both forward and reverse direction depending on the requirement of the application where it is to be installed, for example, like in a conveyor system which would require moving on both direction of items contained in the conveyor table. When such arrangement is necessary for a certain type of application, then a forward reverse motor controller is applied to the control circuit of the electric motor to achieve this purpose. Again the device required for the possibility of this operation is the magnetic contactor. This work is on operating forward and reverse of a direct online starter using contactor.

TABLE OF CONTENTS
COVER PAGE
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWELDGEMENT
ABSTRACT
CHAPTER ONE
INTRODUCTION
1.1      BACKGROUND OF THE PROJECT

• OBJECTIVE OF THE PROJECT
• SCOPE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• LIMITATION OF THE PROJECT
• FEATURES OF DOL STARTING
• APPLICATION OF THE PROJECT

CHAPTER TWO
LITERATURE REVIEW

• REVIEW OF MOTOR STARTERS
• OVERVIEW OF DIRECT ONLINE
• REVIEW OF RELATED STUDIES
• CONTROL APPROACHES OF INDUCTION MOTOR
• REVIEW OF VARIOUS METHODS OF CONTROLLING THE SPEED OF INDUCTION MOTOR

CHAPTER THREE
SYSTEM METHODOLOGY

• PRINCIPLE OF DIRECT ON LINE STARTER (DOL)
• PARTS OF DOL STARTERS
• WIRING OF DOL STARTER
• WIRING DIAGRAM OF DOL STARTER
• WORKING PRINCIPLE OF DOL STARTER
• MOTOR STARTING CHARACTERISTICS ON DOL STARTER

CHAPTER FOUR

• CALCULATE SIZE OF CONTACTOR, FUSE, C.B, O/L  OF DIRECT ON LINE MOTOR STARTER (DOL) 
• CALCULATION OF MOTOR TORQUE & CURRENT
• SIZE OF FUSE
• SIZE OF CIRCUIT BREAKER
• THERMAL OVER LOAD RELAY

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION
• REFERENCES

 

CHAPTER ONE
1.1                                                        INTRODUCTION
An electric motor converts electrical energy into mechanical energy. The reverse of this would be the conversion of mechanical energy into electrical energy and is done by an electric generator.
In normal motoring mode, most electric motors operate through the interaction between an electric motor's magnetic field and winding currents to generate force within the motor. In certain applications, such as in the transportation industry with traction motors, electric motors can operate in both motoring and generating or braking modes to also produce electrical energy from mechanical energy.
Found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives, electric motors can be powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as from the power grid, inverters or generators. Small motors may be found in electric watches. General-purpose motors with highly standardized dimensions and characteristics provide convenient mechanical power for industrial use. The largest of electric motors are used for ship propulsion, pipeline compression and pumped-storage applications with ratings reaching 100 megawatts. Electric motors may be classified by electric power source type, internal construction, application, type of motion output, and so on.
However, for a motor to work or achieve the purpose they are made to do whether in industrial or workshop, they must be controlled. The direct, speed and torque must be controlled by a controller.
A motor controller is a device or group of devices that serves to govern in some predetermined manner the performance of an electric motor. A motor controller might include a manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and faults.
Different starting methods are employed for starting induction motors because Induction Motor draws more starting current during starting. To prevent damage to the windings due to the high starting current flow, we employ different types of starters.
The simplest form of motor starter for the induction motor is the Direct On Line starter. The Direct On Line Motor Starter (DOL) consist a MCCB or Circuit Breaker, Contactor and an overload relay for protection. Electromagnetic contactor which can be opened by the thermal overload relay under fault conditions.
Typically, the contactor will be controlled by separate start and stop buttons, and an auxiliary contact on the contactor is used, across the start button, as a hold in contact. I.e. the contactor is electrically latched closed while the motor is operating.

1.2                             OBJECTIVE OF THE PROJECT
The objective of this work is to design a device for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and faults.

1.3                                SCOPE OF THE PROJECT
This device connect a motor to a power source, such as in small appliances or power tools. The switch may be manually operated or may be a relay or contactor connected to some form of sensor to automatically start and stop the motor. The switch may have several positions to select different connections of the motor. This may allow reduced-voltage starting of the motor, reversing control or selection of multiple speeds. Overload and over current protection may be omitted in very small motor controllers, which rely on the supplying circuit to have over current protection. Small motors may have built-in overload devices to automatically open the circuit on overload. Larger motors have a protective overload relay or temperature sensing relay included in the controller and fuses or circuit breakers for over current protection. An automatic motor controller may also include limit switches or other devices to protect the driven machinery.

1.4                      SIGNIFICANCE OF THE PROJECT

• Most Economical and Cheapest Starter
• Simple to establish, operate and maintain
• Simple Control Circuitry
• Easy to understand and trouble‐shoot.
• It provides 100% torque at the time of starting.
• Only one set of cable is required from starter to motor.
• Motor is connected in delta at motor terminals.

1.5                          LIMITATION OF THE PROJECT

•  It does not reduce the starting current of the motor.
• High Starting Current: Very High Starting Current (Typically 6 to 8 times the FLC of the motor).
• Mechanically Harsh: Thermal Stress on the motor, thereby reducing its life.
• Voltage Dip: There is a big voltage dip in the electrical installation because of high in-rush current affecting other customers connected to the same lines and therefore not suitable for higher size squirrel cage motors
• High starting Torque: Unnecessary high starting torque, even when not required by the load, thereby increased mechanical stress on the mechanical systems such as rotor shaft, bearings, gearbox, coupling, chain drive, connected equipments, etc. leading to premature failure and plant downtimes.

1.6      FEATURES OF DOL STARTING

• For low- and medium-power three-phase motors
• Three connection lines (circuit layout: star or delta)
• High starting torque
• Very high mechanical load
• High current peaks
• Voltage dips
• Simple switching devices

1.7                                          APPLICATION OF THE PROJECT
Industries are using forward and reverse ac motor solutions for process, control of devices such as ac conveyor
Consumer products including electronic toys, home security, gate and garage door openers also make use of this device.

CHAPTER FIVE
5.1                                                           CONCLUSION
Different starting methods are employed for starting induction motors because Induction Motor draws more starting current during starting. To prevent damage to the windings due to the high starting current flow, we employ different types of starters.
The simplest form of motor starter for the induction motor is the Direct On Line starter. The Direct On Line Motor Starter (DOL) consist a MCCB or Circuit Breaker, Contactor and an overload relay for protection. Electromagnetic contactor which can be opened by the thermal overload relay under fault conditions
Most induction motors are started directly on line, but when very large motors are started that way, they cause a disturbance of voltage on the supply lines due to large starting current surges. To limit the starting current surge, large induction motors are started at reduced voltage and then have full supply voltage reconnected when they run up to near rotated speed.
Voltage reduction during star-delta starting is achieved by physically reconfiguring the motor windings during starting the motor windings are connected in star configuration and this reduces the voltage across each winding. This also reduces the torque by a factor of three.
                                                         
5.2                                                    RECOMMENDATION
Direct-On-Line Motor Starter (DOL) is a cost effective method to reduce the power, torque and current required for motor startup. This technique may be used for larger motors and reduces the potential for brownout conditions. Compared to motors that use across-the-line control, Direct-On-Line Motor Starter (DOL) minimizes the number of shock/jolt reduction results. This method, however, does not provide running speed adjustments and only reduces energy usage when starting the motor.
When it comes to choosing the best method of control for your motor systems, it is imperative to account for the characteristics of your application, desired performance and energy usage/savings considerations.

 

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CHAPTER TWO: The chapter one of this work has been displayed above. The complete chapter two of "design and construction of forward and reverse direct online motor starter" is also available. Order full work to download. Chapter two of "design and construction of forward and reverse direct online motor starter" consists of the literature review. In this chapter all the related work on "design and construction of forward and reverse direct online motor starter" was reviewed.

CHAPTER THREE: The complete chapter three of "design and construction of forward and reverse direct online motor starter" is available. Order full work to download. Chapter three of "design and construction of forward and reverse direct online motor starter" consists of the methodology. In this chapter all the method used in carrying out this work was discussed.

CHAPTER FOUR: The complete chapter four of "design and construction of forward and reverse direct online motor starter" is available. Order full work to download. Chapter four of "design and construction of forward and reverse direct online motor starter" consists of all the test conducted during the work and the result gotten after the whole work

CHAPTER FIVE: The complete chapter five of "design and construction of forward and reverse direct online motor starter" is available. Order full work to download. Chapter five of "design and construction of forward and reverse direct online motor starter" consist of conclusion, recommendation and references.

 

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