3. Single-phase T1-transformer with a power of 500 kVA and a single-phase T2- with a power of 400 kVA transformers are connected in parallel and load 1000 kVA with 0.8-back power factor. they are feeding. The equivalent circuit winding resistance of T1 is 0.025 b and the equivalent circuit reactance is 0.06 is b. The equivalent winding resistance of T2 is 0.016 b and the equivalent circuit reactance is 0.07 b. Both has the same conversion ratio in the transformer. a. Draw the connection diagram given in the question. b. Obtain the power sharing expression over the parameters given in the question. c. Calculate the kVA values and power factors of the transformers.

3. Single-phase T1-transformer with a power of 500 kVA and a single-phase T2- with a power of 400 kVA transformers are connected in parallel and load 1000 kVA with 0.8-back power factor. they are feeding. The equivalent circuit winding resistance of T1 is 0.025 b and the equivalent circuit reactance is 0.06 is b. The equivalent winding resistance of T2 is 0.016 b and the equivalent circuit reactance is 0.07 b. Both has the same conversion ratio in the transformer. a. Draw the connection diagram given in the question. b. Obtain the power sharing expression over the parameters given in the question. c. Calculate the kVA values and power factors of the transformers.

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter3: Power Transformers

Section: Chapter Questions

Problem 3.26P: A bank of three single-phase transformers, each rated 30MVA,38.1/3.81kV, are connected in Y- with a...

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A bank of three single-phase transformers, each rated 30MVA,38.1/3.81kV, are connected in Y- with a balanced load of three 1, Y-connected resistors. Choosing a base of 90MVA,66kV for the high-voltage side of the three-phase transformer. spify the base for the low-voltage side. Compute the per-unit resistance of the load on the base for the low-voltage side. Also, determine the load resistance in ohms referred to the high-voltage side and the per-unit value on the chosen base.
In per-unit equivalent circuits of practical three-phase transformers, under balanced thr-phase operation, in which of the following connect ions would a phase-shifting transformer come up? (a) Y-Y (b) Y- (c) -
The ratings of a three-phase three-winding transformer are Primary(1): Y connected 66kV,15MVA Secondary (2): Y connected, 13.2kV,10MVA Tertiary (3): A connected, 2.3kV,5MVA Neglecting winding resistances and exciting current, the per-unit leakage reactances are X12=0.08 on a 15-MVA,66-kV base X13=0.10 on a 15-MVA,66-kV base X23=0.09 on a 10-MVA,13.2-kV base (a) Determine the per-unit reactances X1,X2,X3 of the equivalent circuit on a 15-MVA,66-kV base at the primary terminals. (b) Purely resistive loads of 7.5 MW at 13.2 kV and 5 MW at 2.3kV are connected to the secondary and tertiary sides of the transformer, respectively. Draw the per- unit impedance diagram, showing the per-unit impedances on a 15-MVA,66-kV base at the primary terminals.
Consider the three single-phase two-winding transformers shown in Figure 3.37. The high-voltage windings are connected in Y. (a) For the low-voltage side, connect the windings in , place the polarity marks, and label the terminals a, b, and c in accordance with the American standard. (b) Relabel the terminals a, b, and c such that VAN is 90 out of phase with Va for positive sequence.
For an ideal 2-winding transformer, an impedance Z2 connected across winding 2 (secondary) is referred to winding 1 (primary) by multiplying Z2 by (a) The turns ratio (N1/N2) (b) The square of the turns ratio (N1/N2)2 (c) The cubed turns ratio (N1/N2)3
For a short-circuit test on a 2-winding transformer, with one winding shorted, can you apply the rated voltage on the other winding? (a) Yes (b) No
(a) An ideal single-phase two-winding transformer with turns ratio at=N1/N2 is connected with a series impedance Z2 across winding 2. If one wants to replace Z2, with a series impedance Z1 across winding 1 and keep the terminal behavior of the two circuits to be identical, find Z1 in terms of Z2. (b) Would the above result be true if instead of a series impedance there is a shunt impedance? (c) Can one refer a ladder network on the secondary (2) side to the primary (1) side simply by multiplying every impedance byat2 ?
The rated voltages of a single-phase transformer are 2000 V and 200 V in its primary and secondary respectively. The shunt impedance can be modelled with a resistance of 14000 ohms in parallel with a reactance of 1100 ohm, both refer to primary side. The primary and secondary series impedances are (0.12+j 0.35) ohms and (0.0012+j 0.0035) ohms respectively. A load is connected to the secondary side of transformer, draws 810 KVA with a lagging power factor of 0.85. The load voltage is same as rated voltage, that is 200 V. ▪ Use per unit method for analysis and find the voltage on primary side in pu.
A 50 Hz, Scott connected transformer supplies an unbalanced two phase load at ( 400 V) per phase. For the leading phase the load has a resistance of (13.3 ohm) and capacitor of (318) micro farad in series. For the other phase the load consists of resistance (10) ohm and an inductance of (42.3) mH. Calculate both mathematically and graphically the lines currents on 3- phase side. The main transformer primary to secondary turns ratio is (12/1).
Topic: Special Transformers and Three-Phase Transformers
Draw three transformers for each of the different three-phase connections. That is, draw three transformers and then make the connection, eg star-star, then redraw three transformers and make another three-phase connection, and so on until all four combinations of three-phase connections are made.
In no load phasor diagram of practical transformer, the magnetizing current Imag is with flux Ø O Leading by 30° O Lagging by 60° In phase O 90° out of phase