It is hereby declared that this project and thesis entitled "DESIGN AND CONSTRUCTION OF AUTOMATIC STAR-DELTA STARTER" has been carried out by the following students under my direct supervision and this work has been carried out by them in the laboratories of the Department of Electrical and Electronic Engineering under the Faculty of Engineering of Daffodil International University in partial fulfillment of the requirements for the degree of Bachelor of Science in. 2.3 Motor performance ratings of 120 kW: delta and star connection 13 2.4 Relationship between phase and line currents and voltage 14 5.1 Three-phase motor current rating for star delta 26. Then we would like to take this opportunity to express our appreciation and gratitude to our project - and thesis supervisor Mr.
Mahmudur Rahman, Assistant Professor of Department of EEE for being dedicated to support, motivate and guide us through this project. To our beloved family, we want to give them our deepest love and gratitude for being very supportive and also for their inspiration and encouragement during our studies in this university.
ABSTRACT
CHAPTER -1
INTRODUCTION
- Introduction of Star-Delta Starter
- Problem statement
- Objective
- Methodology
- Thesis outline
Chapter 1: Introduction Chapter 2: Literature Review Chapter 3: Theoretical Model Chapter -4: Hardware Description Chapter -5: Result and Discussions. In this chapter, we first explain the induction motor starting problem and then describe its existing solution. In this chapter some related systems and working principle of induction motor and star starter are discussed.
Chapter 3 is the theoretical model of the project, which describes the working principle of the project. Chapter -4 is the hardware description of components, which describes all the components used in the project. In this chapter, we discuss the conclusion, limitation of the project and future work of the project.
LITERATURE REVIEWS
- Introduction
- STAR-DELTA CONNECTION
- Star or Y-connected system
- Delta or Mesh Connected Circuit
- Theory of Star Delta Starter of Starting of Induction Motor
- Working Principle of Induction Motor & Star-Delta Starter
- Necessity of star delta starter
The current flowing through each coil is called phase current and the current flowing through the main line is called line current. Each coil is connected via a main line and the neutral line, as shown in the figure. Therefore, the voltage across a coil or phase is equal to the voltage between a main line and the neutral.
In delta or mains connection, each coil or phase is connected through two main lines. Star-delta starter, the starting current from the main supply is 1/3 of the delta switching. Starting in a delta, the starting torque is reduced to 1/3 of the starting torque when switching in a delta.
Hence, the equation 3 shown above gives the starting torque of an induction motor in the star-delta starting method. This will cause an electromagnetic force according to Lorentz force law and the rotor will rotate in the same direction as the RMF. Electricity is induced on the rotor bars due to electromagnetic induction rather than direct connection.
This means that the rotating magnetic field will cut the rotor bar at a very high speed. When starting, the stator current must also be high as the rotor and stator currents are coupled due to the operation of the transformer. The main purpose of the star-delta starter is to reduce the high starting current required.
Normally, the starting current of an induction motor is 6 to 7 times the full load current. This will produce a large voltage drop in the line and affect other devices when a powerful induction motor starts. As with larger motors, the starting current can be so high that it can damage the stator coil or even the power cables.
Torque vs. Speed Curve
Current vs. Speed Curve
To really understand the differences between these two starting methods, we will list the values side by side in table 2.3, and on graphs 2.5 and 2. Thus, when the motor is started in the star connection, the phase voltage of the motor is reduced by a factor of √ 3. If we apply this equation for the star delta start, we see from equation 2 where the 67%.
CHAPTER- 3
Design Methodology
Introduction
Block diagram of star-delta starter
Flowchart
CHAPTER-4
Design and Implementation
- Introduction
- Our project consists of following hardware parts
- Magnetic conductor
- Overload Relay
- Timer Relay
- START and STOP push buttons switch
- Cables
- Interlock switches
- Circuit diagram
- Operating principle
There are two basic types of time delay relay- 1.On delay timer or delay on timer. Interlock switches are safety switch connected between star and delta contactor so that one cannot activate without deactivating other contactor. For any fault if star and delta contactors are activated at the same time, the motor will be damaged.
There are main contactors, star switches and delta switches. The main switch and the delta switch are active during operating mode. At the start time, the star relay is active until the auxiliary contactor of the time delay relay is opened. The star switch carries star current and the current is one-third of the rated current.
In the run mode, the main and delta contactor are initially active and after a time, the star contactor is active until the timer contactor contact is de-energized. When the timer contactor is de-energized, the star contactor coil is open and at some point the delta contactor coil is on. The two star and delta contacts are electrically interlocked which means that one is active without the other being deactivated.
Primary push start switch and first activated main contactor and star contactor and timer relay contractor coil. When the star contactor coil is energized and the auxiliary contactor changes its normally open to close state. At the same time, the main delta contactor is active and the motor operates in delta mode.
Star auxiliary close contactor is connected to delta main coil and delta auxiliary close contactor is connected to star main coil. When the star contactor coil is active, the delta contactor coil cannot be active without deactivating the star contactor coil. Similarly when delta contactor coil is active, the star contactor coil cannot be active without deactivating the delta contactor coil.
CHAPTER-5
RESULTS AND COST ANAYLYSIS
- Introduction
- Result
- Three phase motor current rating for star delta starter
- Cost sheet
- Cost comparison
Star delta starter is very common types of starter and widely used, compared to other types of starter. In this project we design star-delta starter which protects the motor from the starting moment. This is the cheapest and safest way to start the induction motor available to others.
CHAPTER-6
CONCLUSIONS
Conclusion
Limitation of the work
Future Scopes
Appendix
