Dielectric Materials Dielectric Substances: Dielectric substance is simply an insulator which can be polarized by means of applied electric field. If a dielectric is placed within an electric field, electric charges don't move throughout the substance as they do in the conductor, but a bit transfer from their average equilibrium position leads dielectrics to polarization. Because of dielectric polarization, positive charges usually are displaced towards the electric field and negative charges shifts towards contrary direction. This generates an internal electric field which minimizes the overall field in the dielectric by itself. If the dielectric is composed of weakly bonded molecules, those molecules not merely turn out to be polarized,
When heat is applied to one of the two conductors or semiconductors, heated electrons flow toward the cooler one. If the pair is connected through an electrical circuit, direct current (DC) flows through that circuit. Fig.1.4 • The voltages produced by Seebeck effect are small, usually only a few microvolts per kelvin of temperature difference at the junction. If the temperature difference is large enough, some Seebeck-effect devices can produce a few millivolts. • Numerous such devices can be connected in series to increase the output voltage or in parallel to increase the max.
INTRODUCTION TO CAPACITOR Capacitors are widely known as an electrical component which is mostly found in power supplies because of their capacity to store energy. They are two terminal electrical elements consisting of two conductor plates which are separated by a dielectric material or insulator, i.e., poor conductor material. They are also referred as condenser they have an ability to store energy in the form of electric charge which produces a static voltage across its plates. The capacitor consists of parallel metal plates which do not touch each other. The capacitors may be some form of a good insulating material such as waxed paper, mica,, ceramic, plastic or some form of a liquid gel as used in electrolytic capacitors.
It also has a very high tensile strength and is a moderately good conductor to heat and electricity. Pure iron is relatively soft, but is significantly hardened and strengthened by impurities in particular carbon. Its surface is usually discoloured by corrosion forming red-brown oxides, since it combines quickly with oxygen of the air in the presence of moisture, but absolutely in dry air it does not rust. The melting point of pure iron is 1,536 C and its boiling point is about 3000 C. Its density is about 7.87 grams per cubic centimetre. It is used more than any other metal for producing metal alloys.
Lithium-ion batteries has been developing and improvised continuously after being introduced commercially in 1991. At present, lithium-ion batteries uses lithium vanadium phosphate as the energy efficiency is much more improved in the forward and reverse reaction compared to other lithium compounds that has been used before. The working principle of a rechargeable Lithium ion does not differ much from an alkaline battery. However, the process of converting chemical energy to electrical energy during discharging of a rechargeable battery produces product that can later be used for the reversed reaction which is the process of converting electrical energy to chemical energy. In simpler manner, the reaction in a rechargeable battery is reversible.
1. INTRODUCTION 1.1 BACKGROUND AND MOTIVATION In the recent years, an extensive advancement in the field of phosphors has been bloomed by deliberately introducing trivalent rare earth ions (lanthanides) as luminescent centers (dopants) in different host matrices to produce rare earth activated phosphors for lighting applications. A phosphor literally, light bearer is a material capable of absorbing energy and re-emitting it in the form of light (ultra violet, visible or Infrared). In general, Most of the phosphors are usually made up of a host material (matrix) and dopant. The host material is normally an insulator or a semiconductor with a wide band gap and it serves to accommodate the dopant.
Silicon first replaced the vacuum tube transistor mainly for their unusually large size and the excessive power consumption. Vacuum tube transistors were also known as thermionic triodes. The vacuum tubes had an operational advantage over the Si transistors purely because the electron mobility is better in vacuum than in Si. Silicon transistors were less immune to electro-magnetic interferences and weren’t then suitable for high frequency applications but that was hardly a deal breaker compared to the size reduction and minimized power consumption. Hence Si was chosen to lead the electronics industry henceforth.
In general, epoxies are stiffer and stronger, but more brittle than polyesters, it also has wide variety of properties. Epoxies also retain their properties better in high temperatures than polyesters do, but epoxies are expensive and has a long curing time. On the other hand, polyester has faster cure time and cheaper than epoxy, but has lower variety of properties than epoxy. When we look at phenolic’s propeties, it has many positive properties that epoxy and polyester do not have. These materials are much like a thermoplastic material at room temperature but change to a thermosetting material at elevated temperature.
1.6.5 MATRIX CONVERTER(Fig. 1.6.5) A matrix converter is a direct power-conversion topology that can convert energy from an AC source to an AC load without the need for bulky and limited-lifetime energy storage elements in the dc link.Matrix-converter topologies can be divided into two types: direct matrix converters (MCs) and indirect matrix converters(2MCs). Even though this topology has some disadvantages, such as limited voltage transfer ratio (0.86)and a high number of power semiconductor device requirements,the matrix converter has received extensive research attention due to its significant advantages: adjustable input power factor, regeneration capability, and high-quality input current waveforms.This topology has the advantage that generated voltage of PMSG is converted into desired AC output voltage without theneed of any intermediate AC to DC conversion stage. In [Alejandro Garces, Marta Molinas et.al Jan. 2012]the output of PMSG is converted by a Reduced Matrix Converter (RMC), placed in the nacelle of each turbine, into ahigh frequency single phase AC voltage. A high frequencytransformer of reduced weight and size is used for insulationpurposes.
As the name implies, BLDC motors do not use brushes for commutation; instead, they are electronically commutated. BLDC motors have many advantages over brushed DC motors and induction motors. A few of these are: • Better speed versus torque characteristics • High dynamic response • High efficiency • Long operating life • Noiseless operation • Higher speed ranges In addition, the ratio of torque delivered to the size of the motor is higher, making it useful in applications where space and weight are critical factors. 1.1.1 STATOR: The stator of a BLDC motor consists of stacked steel laminations with windings placed in the slots that are axially cut along the inner periphery. Traditionally, the stator resembles that of an induction