Q/ 30-kVA, 2200/220-V, 50-Hz distribution transformer is tested for efficiency : and regulation as follows O.C. test( Low voltage side ) : 220 V 4.2 A, 148 W 10.5 A, 360 W S.C. test ( Low voltage side ) : 86 V نقطتان )2( Equivalent reactance referred to primary & referred to * secondary. .ohm, .ohm 6.71 , 0.0671 9.51 , 0.0951 7.51 , 0.0751 8.51 , 0.0851 نقطتان )2( The working current and resistance component of no-load are.. .amper, . .ohm 0.87, 556.89 0.67, 436.89 0.76, 326.89 0 57 236 89

Q/ 30-kVA, 2200/220-V, 50-Hz distribution transformer is tested for efficiency : and regulation as follows O.C. test( Low voltage side ) : 220 V 4.2 A, 148 W 10.5 A, 360 W S.C. test ( Low voltage side ) : 86 V نقطتان )2( Equivalent reactance referred to primary & referred to * secondary. .ohm, .ohm 6.71 , 0.0671 9.51 , 0.0951 7.51 , 0.0751 8.51 , 0.0851 نقطتان )2( The working current and resistance component of no-load are.. .amper, . .ohm 0.87, 556.89 0.67, 436.89 0.76, 326.89 0 57 236 89

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 3.4P: A single-phase 100-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down...

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A single-phase 100-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down transformer. The load, which is connected to the 240-volt secondary winding, absorbs 60 kVA at 0.8 power factor lagging and is at 230 volts. Assuming an ideal transformer, calculate the following: (a) primary voltage, (b) load impedance, (c) load impedance referred to the primary, and (d) the real and reactive power supplied to the primary winding.
An infinite bus, which is a constant voltage source, is connected to the primary of the three-winding transformer of Problem 3.53. A 7.5-MVA,13.2-kV synchronous motor with a sub transient reactance of 0.2 per unit is connected to the transformer secondary. A5-MW,2.3-kV three-phase resistive load is connected to the tertiary Choosing a base of 66 kV and 15 MVA in the primary, draw the impedance diagram of the system showing per-unit impedances. Neglect transformer exciting current, phase shifts, and all resistances except the resistive load.
Consider Figure 3.25 of the text for a transformer with off-nominal turns ratio. (i) The per-unit equivalent circuit shown in part (c) contains an ideal transformer which cannot be accommodated by some computer programs. (a) True (b) False (ii) In the - circuit representation for real c in part (d), the admittance parameters Y11 and Y12 would be unequal. (a) True (b) False (iii) For complex c, can the admittance parameters be synthesized with a passive RLC circuit? (a) Yes (b) No
A single-phase, 50-kVA,2400/240-V,60-Hz distribution transformer has the following parameters: Resistance of the 2400-V winding: R1=0.75 Resistance of the 240-V winding: R2=0.0075 Leakage reactance of the 2400-V winding: X1=1.0 Leakage reactance of the 240-V winding: X2=0.01 Exciting admittance on the 240-V side =0.003j0.02S (a) Draw the equivalent circuit referred to the high-voltage side of the transformer. (b) Draw the equivalent circuit referred to the low-voltage side of the transformer. Show the numerical values of impedances on the equivalent circuits.
An ideal transformer has no real or reactive power loss. (a) True (b) False
Consider Figure 3.4. For an ideal phase-shifting transformer, the imda nce is unchanged when it is referred from one side to the other. (a) True (b) False
The transformer of Problem 3.16 is supplying a rated load of 50 kVA at a rated secondary voltage of 240 V and at 0.8 posr factor lagging. Neglect the transformer exciting current. (a) Determine the input terminal voltage of the transformer on the high-voltage side. (b) Sketch the corresponding phasor diagram. (c) If the transformer is used as a step-down transformer at the load end of a feeder whose impedance is 0.5+j2.0, find the voltage VS and the power factor at the sending end of the feeder.
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 the transformer in Problem 3.10. The open-circuit test with 11.5 kV applied results in a power input of 65 kW and a current of 30 A. Compute the values for GcandBm in siemens referred to the high-voltage winding. Compute the efficiency of the transformer for a load of 10 MW at 0.8 p.f. lagging at rated voltage.
(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 efficiency of a 20 kVA 15.4 / 0.4 kV three-phase power transformer is 79.1% for a load with unit power factor at rated power. Transformer Relative short circuit voltage% Uk = 30.0 and relative idle current% I0 = 30. Since the transformer is connected star-delta; Note: In 3-phase electrical machines, the current-voltage information given on the label is always line values. Phase value When given, it must be specified separately. Therefore, all current-voltage information given in the question are line values. 1-Draw the primary reduced equivalent circuit. 2-What is the power value measured in the short circuit test of this transformer? -The value of iron losses of this transformer what?
The efficiency of a 20 kVA 15.4 / 0.4 kV three-phase power transformer is 74,1% for a load with unity power factor at rated power. Relative short circuit voltage% Uk = 30.0 and relative no-load current% I0 = 30. Since the transformer (Star-delta) is connected; Note: In 3-phase electrical machines, the current-voltage information given on the label is always line values. Phase valueWhen given, it must be specified separately. Therefore, all current-voltage information given in the question are line values. 1-) Draw the primary reduced equivalent circuit. 2-) What is the power value measured in the short circuit test of this transformer? 3-) What is the iron loss value of this transformer ?