Design and Simulation of Automatic Load Tap Changer

Design and Simulation of Automatic Load Tap Changer   Introduction CE 3.1 This is the third project I did as a graduate Electrical Engineering while pursuing my Bachelor of Engineering in the field of Electrical Engineering from Balochistan University of Engineering and Technology, Balochistan, Pakistan. I wanted to conduct a project that would enable the transformer to attain different voltage levels using a load tap changing transformer and thus wanted to learn about different electrical/electronic components that would be needed and thus learn about its design and how to implement it. I was able to improve my written and oral presentation skills as well as my interpersonal skills by the successful completion of this project. Background CE 3.2 For my third project as an undergraduate in electrical engineering, I wanted to start working on a project during my second year. I wanted to learn about the different and commonly used electrical/electronic components, the working mechanism and the implementation in complex projects. This served as a motivation to conduct a project on Load Tap changers. I had studied during my bachelors that Transformer Load changers are an integral part to any power grid whether in big projects or small. I knew that there were the Mechanical Load tap changer and the Electronic Load Tap Changer. I wanted to design an automatic Electronic type Load tap changer to the problems with reliability and maintenance of the Mechanical type.Also, I learned that by using Thyristors to take the on-load current while the main contacts change over from one tap to the next, the design would have no moving parts and thus have a longer service life. And it is due to this reason that I selected the Design of Automatic Load Tap Changer for my project. CE 3.3 The objective of this project is to design and build a prototype of a fully electronic on load tap changer for power transformers by using Triacs as switching devices and microcontroller as the triggering circuit. CE 3.4 CE 3.5 I successfully completed this project by engaging in the following activities: I divided my project into Power circuitry and Control circuitry. I designed the power circuitry to basically consist of a tapping transformer connected to the load through the switching devices. I designed the Control circuitry to sense the voltage signal fed from the step down transformer and compare it to a pre-set reference value. I used a Triac which is a three terminal semiconductor for controlling the current in both directions. I used a Power Circuit, Microcontroller Unit, Analog To Digital Converter, Zero Crossing Detector, Multiplexer, LCD, Buzzer as the parts of the circuit I completed the project within the time frame specified by the university. I conducted detailed literature review on all the components used here. Personal Engineering Activity CE 3.6 I approached a professor with an idea of conducting a project with transformers. Along with my team mate, I had a lot of brainstorming sessions and review meetings with my project supervisor to select a suitable topic. I suggested that I work on a project that was concerned with designing and fabricating a system based on Automatic Electronic Load Tap Changer of a Transformer and the supervisor agreed to this and asked us to begin working on this by first conducting a literature review on all the components we would require and the working of this project and to start working on this project. CE 3.7 I first started with the design of the Power circuitry which consists of our main Tapping Transformer. The tapping is provided at 231V, 225V, 220V, 214V, 209V and 0V. Furthermore, I decided to incorporate BTA16 Triacs. I also decided to build a snubber circuit using 100ÃŽÂ © resistor and a 104pF capacitor. I decided to use the Triac instead of the SCR because a triac operates in the same way as the SCR however it operates in both forward and reverse directions. Also, I had to ensure the TRIAC will turn off correctly at the end of each half-cycle of the AC power. And due to this reason I used the snubber circuit to assist in the turning off and on. I used a MOC 3021 to assist with this. Circuitry Diagram The following are the components I used for this project: I used the AT80S8252 Microcontroller or the 89C52 which is a high performance CMOS 8bit microcomputer of sorts. ADC 0804 Analog to Digital Controller which feeds the input to the microcontroller. I used a step down transformer to provide samples to the ADC of the load.-   Zero Crossing Detector to provide the required pulses for the AND logic along with the multiplexer. A Multiplexer or Mux is a device that selects one of several analog or digital input signals and forwards the selected input into a single line.In my project, the Interlocking mechanism is achieved by using Multiplexer. Thus, at any instant of time, no two triacs would be in their ON STATE. This is particularly important and advantageous in case the logic of microcontroller fails. I used a Liquid Crystal Display (LCD) to display the output voltage that would be across the load side. I used an Optocoupler MOC 3021 to transfer signals between different elements of a circuit. CE 3.8 The following is the manner of the working of this project using a block diagram: The block diagram shows the basic strategy, as to how the Load Tap Changer will work automatically. I used TRIACs as the switching devices. I made sure that the The transformer has five tappings at the voltage level. Each of these tappings is connected to the one of the main terminals of the TIRAC. The second main terminals of all the five TRIACS have been shorted. So at any given time when any of the TRIAC has been switched on there is only one conducting path to the load. I used a step down transformer to step down the voltage level to instrumentation levels so that it can be used in the control circuitry. As the voltage increases or decreases depending on the nature of the load the voltage at the primary of the step down transformer varies, resulting in an equivalent variation at the secondary side. I then had to make sure that this sampled AC voltage is rectified to an almost smooth DC value. This DC voltage is then fed to the analog to digital converter, which gives a digital output that can be understood by the microcontroller. The ADC output is fed to the microcontroller which had been already programmed to compare this incoming value to a set of predefined values and send a high signal on one of its port bits. The output of the microcontroller is fed to a multiplexer. It is incorporated to ensure that at any given time, even if the logic fails there is only 1 conduction path to the load. I.e. only one TRIAC is switched on at any instance in time. I also used the zero crossing detector in order to detect the instance when the AC voltage crosses the zero amplitude mark. The output of this zero crossing detector is in the form a pulse generated every half cycle. I then fed the output of the zero crossing detector and the multiplexer to the AND logic as shown in the diagram. Each time the zero crossing detector gives an output, a pulse is generated at the output of the AND logic This output of the AND logic is basically our trigger signal for the switching devices i.e. the TRIACs however in order to isolate the control and high voltage circuitry and to implement DC triggering on the TRIACs operating at AC voltages the Optocouplers have been incorporated. So basically the Optocouplers are only there to provide isolation. CE 3.9 The following are simulation results I obtained: When input is 220v, the Triac on Tap 3 is on. When the input is 225v, the Triac on Tap 2 is on. Summary CE 3.10   Ã‚   I successfully completed the project titled Design and Simulation of Automatic Load Tap Changer along with my team mate. I learned how to build a circuit board and how all the different electrical components talk to each other in this project. I learned how important the Load Tap Changer is for any power grid and how useful it is over the Mechanical type Load type changer. By successfully completing this project, I was able to improve my written, oral and interpersonal skills.

A Journal of Woe Essay

The pain was excruciating as I struggled to fight for my life under the pillow that my beloved husband had forced upon me. I remember how much it hurts as I tried to gasp for air beneath Othello’s powerful arms. I can recall those murderous eyes driven mad by jealousy and hate. For an instant, I failed to recognize the man I have fought to love. I cannot recognize that man I secretly married despite my father’s objections. For a moment, I failed to see the man who promised to love me for the rest of our lives. It all started that fateful night when Othello fired Michael Cassio from his lieutenant position. He accused me of sleeping with Cassio. The jealousy was probably most triggered when he felt that I was being too concerned with Cassio’s situation. He must have thought that my acts in favor of Cassio’s defense were signs of affection for him. He accused me of giving Cassio the handkerchief which was a gift from him. There is no way I would have given such a valuable gift to someone else! My love and affection is undividedly offered for Othello. It does not seek other men aside from him. My fidelity to my marriage and to my husband is pure and untainted. How could he even dare think of me with such immorality! However, it was too late to defend myself further, for the fire in his eyes was already consumed with too much evil to pay any heed to my cries. Yet, before death consumed what was left of my body, the image of the man I love came before my eyes. I forgive him. He is a victim and not a murderer. I know in his heart that he loves me still, and once this madness brought about by his jealousy ends, he would repent and ask for forgiveness. Or, he might end his life as well to follow me, so he can make it up to me personally—and I will be waiting on the other side.

Attempting to Define Art - 993 Words

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There may not be a â€Å"Unified Theory of Aesthetics,† but works of art are open to critical assessment. Unfortunately, the three characteristics I listed are too broad to be satisfying; yet anything I can think to add would be too exclusive. Some art communicates ideas and values, but not all of it. Some art captures beauty, but other art expresses ugliness. Some art doesn’t really communicate and express anything beyond an aesthetically pleasing (whatever that means) use of a medium. Another possible problem with these general characteristics of art is that they do not exclude the productions of animals. The music of songbirds is not generally considered art to us, but to birds it may be. This is not a minor point: while human art exists in a more complicated social context, our capacity for it is something we evolved. Our complex and varied aesthetics may be the outgrowth of biological urges to produce and receive art, just as the bird’s singing comes from an innate impulse. 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The American Identity - 2684 Words

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