Explain working of three-phase transformers, Electrical Engineering

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.

Posted Date: 6/27/2013 12:20:36 AM | Location : United States

Related Discussions:- Explain working of three-phase transformers, Assignment Help, Ask Question on Explain working of three-phase transformers, Get Answer, Expert's Help, Explain working of three-phase transformers Discussions

Write discussion on Explain working of three-phase transformers
Your posts are moderated
Related Questions
L filters: An L filter contains two reactive elements that are one in series and one in parallel. T and π filters: Main article: Capacitor-input filter

Q. For the configurations of the coupled coils shown in Figure, obtain the voltage equations for v 1 and v 2 .

A 300 km, 3-phase, 50Hz transmission line has spacing as shown in Figure. Each phase of the line consists of a bundle of three conductors. (a) Find the total per-phase inductanc

Q. Obtain the truth table for the logic block shown in Figure

a. With neat circuit diagram and frequency response curve define the two stages RC coupled amplifier. What are its benefits and applications? b. Sketch ideal and the actual resp

Octal to binary Conversion Conversion form  octal to binary  is the reverse  of this process. Express each  octal digit  in three bit  binary  equivalent. Ex. Convert 3576

Q.9 What are the main differences between VGA and CGA graphics adapters? Ans: Colour Graphics Adapter (CGA), initially also known as Colour/Graphics Adapter or IBM Colo

Give an industrial look at modern CAM/CAD. Define explicit, implicit and parametric representations. What are the basic advantages of parametric representations over the impli

Bias circuit requirements: Signal requirements for Class A amplifiers The Q-point is placed thus the transistor stays in active mode (does not shift to operation in the s

A 440v 4-pole dc generator takes an armature current of 50A when rotating at 626 rpm. the armature circuit resistance is 0.25 ohms. determine the generated emf?