Transformer rating indicated in (kVA)in light of the fact that copper loss of a transformer relies upon current andiron misfortune on voltage. Along these lines, add up to transformer reliesupon volt ampere (VA) and not on stage point amongst voltage and current. It isfree of load power factor. That is the reason rating of transformer in (kVA)and not in KW(kilowatt). 5. Why transformerrating specified in KVA?Thefour fundamental setups of a three-stage transformer, we can list thetransformers optional voltages and streams as for the essential line voltage,VL and its essential line current IL as appeared in the accompanying table.
Where: n breaks even with the transformers “turns proportion” (T.R.)of the quantity of optional windings NS, partitioned by the quantity ofessential windings NP. (NS/NP) and VL is the line-to-fix voltage with VP beingthe stage to-unbiased voltage. Three phase transformerline and voltage current. Where once more, VL is the line-to-linevoltage, and VP is the stage to-unbiased voltage on either the essential or theoptional side.
Three phase voltage and current. (vi) Scottconnection- Twotransformers are utilized as a part of this sort of association. One of thetransformers has focus taps on both essential and auxiliary windings.
Scott-association can likewise be utilized for three stage to two stage change. (v) Open delta connection- Opendelta association can be used when one of the transformers in delta-delta isincapacitated and the administration is to be continued until the point whenthe defective transformers is repaired or supplanted.(iv) Delta-starconnection- The essentialwinding is related in delta and the optional winding is related in star withunbiased grounded. This sort of connection is fundamentally used in step uptransformer toward the begin of transmission line. (iii) Star-delta connection-The essential winding is star-star associated with grounded impartial and thesecondary winding is delta associated. Step down transformer at the substationend of transmission line is mainly utilized for this connection. (ii) Delta-deltaconnection –Generally, large and low voltage transformer use this connection.Number of required turns is decently greater than star-star association.
Thisconnection can be used notwithstanding for unbalanced loading. Regardless ofwhether one transformer is not balanced, system can keep on operating in opendelta association is one of the benefit of the connection (i) Usually small, high voltage transformersuse Star-star connection. In starconnection number of required turn is reduced. Thus, reduction of the amount ofinsulation also takes place. (star-star), (delta-delta), (star-delta), (delta-star), (open-deltaconnection), (scott connection)Staror delta can be connected in the winding of primary or secondary windings.
Itwill provide a total of 4 possible connections for 3 phase transformer.Threephase transformer connectionIn a shell type three phasetransformer, three stages are more autonomous than they are in core type. Eachstage has its individual magnetic circuit. The development of shell type threestage transformer is shown in the figure above. The advancement resembles thatof three single stage shell form transformers kept on the most noteworthypurpose of each other.
The advancement of a centre kindthree phase transformer is as showed up in the figure. The core contains threelegs or limbs. Obviously, the centre is contained thin overlaid sheets todiminish eddy current hardships. Each limb has fundamental and auxiliarywindings in cylindrical shape. Three phase ac systempresent in almost all major generation and distribution systems in the world.It constructed from 3 single phase transformers. A three-stage transformer isset up by three arrangements of essential and auxiliary windings, each setwound around one leg of an iron center get together.
Fundamentally it wouldseem that three single-stage transformers sharing a joined center as in figure.Three phase transformer center contains three arrangements of windings. Thosearrangements of essential and optional windings will be associated in either ?or Y setups to shape a whole unit. 3. Three phase transformer (operation andtypes)Presently we will examine the saving of copper in autotransformer contrasted with two windings electrical power transformer. Werealize that weight of copper of any winding relies on its length and cross -sectional zone. Again length of conductor in winding is corresponding to itsnumber of turns and cross – sectional area changes with evaluated current.
Soweight of copper in winding is straightforwardly corresponding to result ofnumber of turns and evaluated current of the winding. 2.How copper is saving in autotransformer?3. Absent of galvanic isolation.2. Used just in theconstrained places where a slight variation of the output voltage from inputvoltage is required.
1. The auxiliary winding isn’t protected from theessential winding. On the off chance that an auto transformer is utilized tosupply low voltage from a high voltage and there is a break in the auxiliarywinding, the full essential voltage comes across the optional terminal which isrisky to the operator and equipment. Disadvantages of auto transformer. 3. higher efficiencythan two winding transformer.
2. voltageregulation as voltage drop in resistance 1. smaller in size and cheaper.
Advantagesof auto transformerExampleof step down transformer. The picture shows that number of primary higher thannumber of secondary coil. B.
Step Down Transformer- Atransformer in which Np >Ns is called a step down transformer. A step downtransformer is a transformer which converts high alternating voltage to lowalternating voltage.Exampleof step up transformer. The picture shows that Ns>Np.
A. Step Up Transformer –At the point whenthe number of secondary coil is higher than the primary coil, it will be calledas step up transformer. It converts low alternative voltage to high alternativevoltage.Principleof working operation.
Alongthese lines, the part of the windings passes on the contrast between the twocurrents cab be made from a smaller conductor size, since the currents are muchsmaller saving on the cost of an equivalent double wound transformer. An autotransformer is used principally for theadjustments of line voltages to either change its value or to keep itconsistent. If the voltage modification is by a small amount, either up ordown, at that point the transformer ratio is small as Vp and Vs are almostequal. Currents Ip and Is, are also nearly equivalent.
Auto transformer terminalmarkings. The standard procedure for denoting an auto transformerwinding is to name it with capital letters. Essentially the normal unbiasedassociation is set apart as N or (n). For the secondary tapping’s, suffix numbersare utilized for all tapping points along the auto transformer secondarywinding. These number generally begin at number1 and continue in ascendingorder for all tapping points as shown.
Autotransformer with multiple tappingpointsThe autotransformer canalso be constructed with more than one single tapping point. Auto-transformerscan be utilized to provide different voltage points along its winding orincrease its supply voltage concerning its supply voltage VP as shown.Atthe point when the essential current Ip, is moving through the single windingtoward the arrow as shown up, the secondary current, Is, streams in theopposite direction. Along these lines, in the part of the winding thatgenerates the secondary voltage, Vs the present streaming out of the winding isthe difference of Ip and Is. Thestreams of the essential and optional windings are streaming on the contraryheadings, so the aggregate current moving through the regular piece of thewinding is equivalent to the contrast between the current on the low-voltagewinding and the current on the high-voltage winding. All together for anautotransformer to work legitimately, the two windings ought to have a similarwinding sense.
Theguideline of operation of the transformer is the same as the one of the regulartransformer, at that point the connection amongst information and yieldvoltages and info and yield streams and the proportion of number of turnsbetween the essential and the auxiliary winding is the same. Theautotransformer has just a single winding. In this unique sort of transformer,some portion of the winding is basic to both the essential and the optionalone. A variable autotransformer· Construction: Auto transformer is a thatwith just a single twisting wound on a covered center.
An auto transformer is similar to a two winding transformer however contrast inthe way the essential and auxiliary winding are interrelated. Both essentialside and optional side is regular to a piece of the winding. On stackcondition, a piece of the heap current is acquired straightforwardly from thesupply and the rest of the part is gotten by transformer activity. An Autotransformer works as a voltage regulator.· Introduction:1) AutoTransformer