Chapter 2
2.1 Frequency Converter From the electric energy conversion point of view we distinguish four basic converter types
(Pavelka and Čeřovský, 2002). Rectifiers convert an input AC voltage and current to an output DC voltage and current, choppers convert an input DC voltage and current to an output DC voltage and current of different values, inverters convert an input DC voltage and current to an output AC voltage, current, frequency and count of phases, AC converters convert an input voltage, current, count of phases and frequency to an AC energy with different parameters. The frequency converters that convert an input frequency to an output frequency and that simultaneously maintain the count of phases create a subgroup of AC converters
As a result it requires a special multi-winding transformer - so it is not a transformer less topology any more. This is the biggest disadvantage of the cascaded H-bridge inverter. However, there is a possibility to use capacitors as voltage sources in bridges and to develop a suitable control strategy for the stabilization of capacitor voltages, generally speaking. Another disadvantage is the high number of power electronic devices. The cascade multilevel inverter consists of a number of H-bridge inverter units with take apart dc source for each unit and is related in cascade or series as shown in Fig. 2.6 (a). Each H-bridge can generate three different voltage levels: +Vdc, 0 and –Vdc by connecting the dc source to ac output side by different combinations of the 4 switches S1, S2, S3, and S4.Cascaded-H bridge topology is used to give suppleness for expansion of the number of levels easily without introducing under complexity in the power circuit. The series H-bridge inverter appeared in
They untested it and presented its various advantages in 1997. Since then, the CMI has been utilized in a wide range of applications and shows dominance in high-power applications. The ac output of each H-bridge is related in series such that the synthesized output voltage waveform is the amount of all of the individual H-bridge outputs. By concerning sufficient number of H-bridges in pour and using proper modulation scheme, a nearly sinusoidal output voltage waveform can be synthesized. A three-phase CMI topology is basically composed of three identical phase legs of the series-chain of H-bridge converters, which can possibly produce different output voltage as shown in Fig. 2.5.The number of levels in the output phase voltage is 2S+1 and 4S+1 respectively, where S is the number of H-bridges used per phase. For example, on 1- H-bridge and 2- H-bridges per phase are explained for 3-level, and 5-level multilevel inverter
Contents Page Section 3 ……………… …………………… Introduction 3 ……………… …………………… The Pioneers of the Electronic Age 4 ……………… …………………… The Theory of the Synthesiser 5 ……………… …………………… Other Changes Due to Electronic Technology 6 ………………
Alternative energy sources are renewable, and is most commonly referred to as free energy sources. There are many alternative energy sources such as hydro power, solar power, wind, biomass, and geothermal. Using alternative sources is more expensive in the long run, but it is the much safer option for our environment compared to fossil fuels. Although everything used is completely free, such as water and wind, the equipment used to generate these things are expensive. There are several pros and cons that come with the utilization of alternative energy sources.
There is big deal of interest in silicon carbide (SiC) as an electronic material for high-voltage, high-power and high temperature applications. In this thesis, characteristics of Double gate vertical metal semiconductor field effect transistors (MESFET) fabricated on N/N+ 3C-SiC grown on N+ Si substrate are reported. The most intriguing electronic property of silicon carbide is that it is the only semiconductor material other than silicon that can have electronically passivated surface to industrial standards. The surface passivation is the main reason for the dominance of silicon but, in addition to that, silicon carbide has superior bulk properties. This combination of factors raises the question whether silicon carbide can play a role in main stream electronics (integrated-circuit based complex systems). After analysis of both technical and commercial factors and challenges leads to a conclusion that developing a silicon-carbide film on silicon wafers is the most promising way for silicon carbide enter the mainstream electronics. SiC MESFET shows great promise in high power/temperature operations when compared to Si counter parts. The simulations were performed on ATLAS (SILVACO) software, and results are presented.
The emergence of the Microgrids came after realizing that the architecture of the electricity grid existing nowadays (Figure 1) is getting obsolete, since it is based on the idea of a top-down system, which is predicated on unidirectional energy flows. [ASMUS09]
In thermodynamics Refrigeration is the major application area, in which the heat is transferred from a lower temperature region to a higher temperature region. The devices which produce refrigeration are known as Refrigerators and the cycle on which it operates are called refrigeration cycles. Vapour compression refrigeration cycle is the most regularly used refrigeration cycle in which the refrigerant is alternately vaporized and condensed and in the vapor phase it is compressed. Gas refrigeration cycle is the well-known refrigeration cycle in which cycle refrigerant remains in the gaseous phase throughout the cycle. Cascade refrigeration are the other refrigeration cycles discussed in this chapter; absorption refrigeration is the one more refrigeration cycle which is used where the refrigerant is dissolved in liquid before it is compressed. One more refrigeration in which refrigeration is produced by passing the electric current through two dissimilar materials is called as the thermoelectric refrigeration.
· B-phase transformer (EMTU-TT01) · Feedback electronic wattmeter · Multi-range moving-iron ammeter · Instrument voltage transformer THEORY AND INTRODUCTION ----------------------- Transformers are used all over the world to step-up and step-down electricity. The transformer is one of the most commonly used electrical devices. The reason the transformer is so popular is because they range in size from 240V to well over 240kV, stepping -up and stepping-down electricity all over the world.
AC and DC literally stand for Alternating Current and Direct Current. Direct Current is very convenient and is used in many modern day utilities. For a circuit with DC the current is constanly in one direction, while the voltage remains constant. This makes for a simplistic circuit, for example a flashlight, The batteries are a source of electrochemical DC power and . However AC is called Alternating Current because the voltage changes from negative to positive a given number of times a second, this is also described as the frequency of the power. An example of this would be a motor ran by a hand crank. The inversing of charges creates a sinusoidal graph which looks something like figure 1 (given in radians). This makes for an unsteady power source and can often times be warped from the sinusoidal shape. So the main difference between AC and DC is the way the energy is transmitted.
Alternating current is always changing in direction and amplitude. The current flow in alternating current changes in even intervals. Ac usually changes in power and direction. The vast majority of power supplied for households and big business is alternating current. This is because of the ease of generating alternating current in alternators. The main concept of alternators is moving a conductor through magnetic lines. The change in the magnetic field around the conductor or vice versa makes electrons move. When you have physically moved either the conductor or magnet in a complete 306-degree circle you have produced one sine wave or one complete cycle. The amount of time it takes to complete one cycle is referred to as a period. The frequency of an alternating sine wave is the amount of cycles per second. Frequency is measured in hertz. One hertz is equivalent to one cycle per second. The frequency coming out of your electrical plug at home is 60 Hz. The peak value in a sine wave is the top voltage level away from zero. The peak-to-peak voltage value is referring to difference between the positive peaks value to the negative peak value. The effective or rms value of a sine wave is the actual amount you would use or measure using a multi-meter. In three-phase alternating current there are three different coils or conductors that produce three different sine waves.
In this thesis, MATLAB/SIMULINK (version 11) software has been used to design and develop the control circuit for dc to ac conversion and analyze simulation in MATLAB environment along with Simulink and power system block set (PSB) toolboxes. The name MATLAB symbolizes for MATrix LABoratory. MATLAB was written initially to give easy access to matrix software developed by the LINPACK (linear system package) and EISPACK (Eigen system package) projects.
Basic Mathematics for Electronics seventh edition: Nelson M. Cooke, Herbert F.R Adams, Peter B. Dell, T. Adair Moore; Copyright 1960
In this paper, I will talk about how AC circuits can be described by considering voltage and current using complex numbers. An AC circuit requires two separate numbers to be able to completely describe it. This is because it takes into account the amplitude and the phase of the current. The fact that complex numbers can be easily added, subtracted, multiplied or divided with each other makes them ideal for this operation where both amplitude and phase have to work together.
In this thesis, CMOS Current Conveyors for high frequency applications have been presented. current conveyor, namely, Second Generation Current Conveyor (CCII) has been analyzed and designed using TSMC 0.18μm CMOS technology process parameters. The simulation results have been presented to demonstrate the feasibility of the circuits.
It converts the mechanical energy of the rotating shaft caused by wind into electrical energy (Correla, 1986). The focus of this research will be limited to devices that operate as electrical motors.... ... middle of paper ... ...
How did technology affect us? Did it affect us in a positive or a negative way? Technology has both positive and negative effects, it’s plainly about how people choose to use it. Throughout these years, technology has been a great advancement for our country and it helped us develop in many ways that we can’t even count.
The concept of this essay is to stress that biofuels are a viable and sustainable energy source than fossil fuels, showing its advantages but not ignoring its disadvantages which also enlightens us about the cleaner and renewable natural resources. Biofuels is an alternative source of energy which can end the global dependence on fossil fuels.