Transformer - Wikipedia. A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. A varying current in one coil of the transformer produces a varying magnetic field, which in turn induces a voltage in a second coil. Power can be transferred between the two coils through the magnetic field, without a metallic connection between the two circuits. Faraday's law of induction discovered in 1. Transformers are used to increase or decrease the alternating voltages in electric power applications. Since the invention of the first constant- potential transformer in 1. ![]() Find energy market research reports and pharmaceuticals industry analysis including industry overviews, market segmentation data, market share and growth. Study Of LANCO 2*600 MW Udupi Thermal Power Plant 1. 1 A Project Report on STUDY OF 600MW THERMAL POWER PLANT UDUPI POWER CORPORATION LIMITED 2*600 MW. International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research. The equivalent circuit of a power system with a PureWave DSTATCOM is shown below. PureWave DSTATCOM generates a variable voltage, V d, that is very nearly in phase. Pvc cable more reliable from. ![]() ![]() ![]() ![]() Transformers range in size from RF transformers less than a cubic centimeter in volume to units interconnecting the power grid weighing hundreds of tons. Basic principles. Ideal transformer. Ideal transformer equations (eq.)By Faraday's law of induction: VS=. Perfect coupling implies infinitely high core magnetic permeability and winding inductances and zero net magnetomotive force. This varying magnetic field at the secondary winding induces a varying EMF or voltage in the secondary winding due to electromagnetic induction. The primary and secondary windings are wrapped around a core of infinitely high magnetic permeability. Difference between Power Transformer and Distribution Transformer (photo credit: dorazioenterprises.com). ![]() With a voltage source connected to the primary winding and load impedance connected to the secondary winding, the transformer currents flow in the indicated directions. However, some sources use the inverse definition. In practice, some flux traverses paths that take it outside the windings. It is not directly a power loss, but results in inferior voltage regulation, causing the secondary voltage not to be directly proportional to the primary voltage, particularly under heavy load. It can be shown that if the percent impedance. VA unit in parallel with 1,0. VA unit, the larger unit would carry twice the current). However, the impedance tolerances of commercial transformers are significant. Also, the Z impedance and X/R ratio of different capacity transformers tends to vary, corresponding 1,0. VA and 5. 00 k. VA units' values being, to illustrate, respectively, Z . Magnetizing current is in phase with the flux, the relationship between the two being non- linear due to saturation effects. However, all impedances of the equivalent circuit shown are by definition linear and such non- linearity effects are not typically reflected in transformer equivalent circuits. With open- circuited secondary winding, magnetizing branch current I0 equals transformer no- load current. This introduces error but allows combination of primary and referred secondary resistances and reactances by simple summation as two series impedances. Transformer equivalent circuit impedance and transformer ratio parameters can be derived from the following tests: open- circuit test. Positively increasing instantaneous current entering the primary winding's dot end induces positive polarity voltage at the secondary winding's dot end. However, properties such as core loss and conductor skin effect also increase with frequency. Aircraft and military equipment employ 4. Hz power supplies which reduce core and winding weight. Hz and 2. 5 Hz) than normal utility frequencies (5. Consequently, the transformers used to step- down the high overhead line voltages (e. V) were much larger and heavier for the same power rating than those required for the higher frequencies. At a lower frequency, the magnetizing current will increase. Operation of a transformer at other than its design frequency may require assessment of voltages, losses, and cooling to establish if safe operation is practical. For example, transformers may need to be equipped with 'volts per hertz' over- excitation, ANSI function 2. One example is in traction transformers used for electric multiple unit and high- speed train service operating across regions with different electrical standards. The development of switching power semiconductor devices and complex integrated circuits made switch- mode power supplies viable, to generate a high frequency from a much lower one (or DC), change the voltage level with a small transformer, and, if necessary, rectify the changed voltage. Energy losses. Real transformer energy losses are dominated by winding resistance joule and core losses. Transformers' efficiency tends to improve with increasing transformer capacity. The efficiency of typical distribution transformers is between about 9. Hysteresis and eddy current losses are constant at all load levels and dominate overwhelmingly without load, while variable winding joule losses dominating increasingly as load increases. The no- load loss can be significant, so that even an idle transformer constitutes a drain on the electrical supply. Designing energy efficient transformers for lower loss requires a larger core, good- quality silicon steel, or even amorphous steel for the core and thicker wire, increasing initial cost. The choice of construction represents a trade- off between initial cost and operating cost. As frequency increases, skin effect and proximity effect causes the winding's resistance and, hence, losses to increase. Core losses. Hysteresis losses. Each time the magnetic field is reversed, a small amount of energy is lost due to hysteresis within the core. According to Steinmetz's formula, the heat energy due to hysteresis is given by. Wh. Eddy currents therefore circulate within the core in a plane normal to the flux, and are responsible for resistive heating of the core material. The eddy current loss is a complex function of the square of supply frequency and inverse square of the material thickness. However, any leakage flux that intercepts nearby conductive materials such as the transformer's support structure will give rise to eddy currents and be converted to heat. This energy incites vibration transmission in interconnected metalwork, thus amplifying audible transformer hum. When windings surround the core, the transformer is core form; when windings are surrounded by the core, the transformer is shell form. At higher voltage and power ratings, shell form transformers tend to be more prevalent. Each lamination is insulated from its neighbors by a thin non- conducting layer of insulation. Thinner laminations reduce losses. The cut- core or C- core type is made by winding a steel strip around a rectangular form and then bonding the layers together. It is then cut in two, forming two C shapes, and the core assembled by binding the two C halves together with a steel strap. When power is then reapplied, the residual field will cause a high inrush current until the effect of the remaining magnetism is reduced, usually after a few cycles of the applied AC waveform. On transformers connected to long, overhead power transmission lines, induced currents due to geomagnetic disturbances during solar storms can cause saturation of the core and operation of transformer protection devices. The higher initial cost of the core material is offset over the life of the transformer by its lower losses at light load. These materials combine high magnetic permeability with high bulk electrical resistivity. For frequencies extending beyond the VHF band, cores made from non- conductive magnetic ceramic materials called ferrites are common. The closed ring shape eliminates air gaps inherent in the construction of an E- I core. The primary and secondary coils are often wound concentrically to cover the entire surface of the core. This minimizes the length of wire needed and provides screening to minimize the core's magnetic field from generating electromagnetic interference. Toroidal transformers are more efficient than the cheaper laminated E- I types for a similar power level. Other advantages compared to E- I types, include smaller size (about half), lower weight (about half), less mechanical hum (making them superior in audio amplifiers), lower exterior magnetic field (about one tenth), low off- load losses (making them more efficient in standby circuits), single- bolt mounting, and greater choice of shapes. The main disadvantages are higher cost and limited power capacity (see Classification parameters below). Because of the lack of a residual gap in the magnetic path, toroidal transformers also tend to exhibit higher inrush current, compared to laminated E- I types. Ferrite toroidal cores are used at higher frequencies, typically between a few tens of kilohertz to hundreds of megahertz, to reduce losses, physical size, and weight of inductive components. A drawback of toroidal transformer construction is the higher labor cost of winding. This is because it is necessary to pass the entire length of a coil winding through the core aperture each time a single turn is added to the coil. As a consequence, toroidal transformers rated more than a few k. VA are uncommon. Relatively few toroids are offered with power ratings above 1. VA, and practically none above 2. VA. Small distribution transformers may achieve some of the benefits of a toroidal core by splitting it and forcing it open, then inserting a bobbin containing primary and secondary windings. The air which comprises the magnetic circuit is essentially lossless, and so an air- core transformer eliminates loss due to hysteresis in the core material. They're also used for resonant transformers such as Tesla coils where they can achieve reasonably low loss in spite of the high leakage inductance. Windings. Windings are usually arranged concentrically to minimize flux leakage. The transposition equalizes the current flowing in each strand of the conductor, and reduces eddy current losses in the winding itself. The stranded conductor is also more flexible than a solid conductor of similar size, aiding manufacture. Coils are split into sections, and those sections interleaved between the sections of the other winding. Power- frequency transformers may have taps at intermediate points on the winding, usually on the higher voltage winding side, for voltage adjustment.
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