Explain working of three-phase transformers, Electrical Engineering

Assignment Help:

Q. Explain working of three-phase transformers?

Transformation in three-phase systems can be accomplished in either of two ways: (1) connecting three identical single-phase transformers to form a three-phase bank (each one will carry one-third of the total three-phase load under balanced conditions); or (2) a three-phase transformer manufactured for a given rating. A three-phase transformer, compared to a bank of three single-phase transformers, for a given rating will weigh less, cost less, require less floor space, and have somewhat higher efficiency.

The windings of either core-type or shell-type three-phase transformers may be connected in either wye or delta. Four possible combinations of connections for the three-phase, two- winding transformers are Y- Δ, Δ -Y, Δ -Δ , and Y-Y. These are shown in Figure with the transformers assumed to be ideal. The windings on the left are the primaries, those on the right are the secondaries, and a primary winding of the transformer is linked magnetically with the secondary winding drawn parallel to it. With the per-phase primary-to-secondary turns ratio (N1/N2 = a), the resultant voltages and currents for balanced applied line-to-line voltages V and line currents I are marked in the figure.

2459_Explain working of three-phase transformers.png

As in the case of three-phase circuits under balanced conditions, only one phase needs to be considered for circuit computations, because the conditions in the other two phases are the same except for the phase displacements associated with a three-phase system. It is usually convenient to carry out the analysis on a per-phase-of-Y (i.e., line-to-neutral) basis, and in such a case the transformer series impedance can then be added in series with the transmission-line series impedance. In dealing with Y- Δ and Δ -Y connections, all quantities can be referred to the Y-connected side. For Δ- Δ connections, it is convenient to replace the -connected series impedances of the transformers with equivalent Y-connected impedances by using the relation.

2044_Explain working of three-phase transformers1.png

It can be shown that to transfer the ohmic value of impedance from the voltage level on one side of a three-phase transformer to the voltage level on the other side, the multiplying factor is the square of the ratio of line-to-line voltages, regardless of whether the transformer connection is Y-Y, Δ -Y, or Δ -Δ . In some cases, where Y-Y transformation is utilized in particular, it is quite common to incorporate a third winding, known as tertiary winding, connected in delta. Such multiwinding transformers with three or more windings are not considered in this text.


Related Discussions:- Explain working of three-phase transformers

Describe what you understand by offset voltage, a. Describe what you unders...

a. Describe what you understand by 'offset voltage' and 'offset current' of op-amp.  Discuss with a neat circuit diagram the method used for minimizing offset voltage and offset cu

Construct a suitable piecewise linear equivalent circuit, Problem: The ...

Problem: The current voltage characteristic [ ID versus VD] of a semiconductor diode for VD > 0 [forward bias] is given in Figure Under reverse bias conditions [VD Fi

Calculate efficiency to load at unity power factor, Q. A 300-kVA transforme...

Q. A 300-kVA transformer has a core loss of 1.5 kW and a full-load copper loss of 4.5 kW. (a) Calculate its efficiency corresponding to 25, 50, 75, 100, and 125% loads at unity

Explain in brief about the robots, Explain In brief about the Robots - ...

Explain In brief about the Robots - Robot is programmed with a series of instructions that enable it to carry out a series of tasks - On the other hand, an operator manually

Find current in bjt, Q. A BJT is biased by the method shown in Figure. If V...

Q. A BJT is biased by the method shown in Figure. If V BEQ = 0.7V, β = 100, V CEQ = 10 V, and I CQ = 5 mA, find I 1 , I 2 , and IEQ.

Explain light-emitting diode, Q. Explain Light-emitting diode? This is ...

Q. Explain Light-emitting diode? This is a reliable, rugged, and inexpensive semiconductor display device requiring about 10 mA of current flow for full illumination. An LED is

., Ask quA 380-V, 15-hp, 50-Hz, four-pole, Y-connected wound-rotor inductio...

Ask quA 380-V, 15-hp, 50-Hz, four-pole, Y-connected wound-rotor induction motor has the following impedances in ohms per phase referred to the stator circuit: R1= 0.453? R2= 0.24

Quality of supply and services - power distribution, Quality of Supply and...

Quality of Supply and Services  - Power Distribution For effectual management and performance improvement it is essential to measure the several defined parameters of the proc

Sign flag - sub subtract instruction , Sign flag Since D 7  bit in ...

Sign flag Since D 7  bit in the  results is 0sign flag is reset. This also  shown that the results is positive.

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd