26. A 200 KVA transformer has an iron loss of 1 kW and full-load Cu loss of 2kW. Its load kVA cor- responding to maximum efficiency is ....... kVA. (a) 100 (b) 141.4 (c) 50 (d) 200 If Cu loss of a transformer at 7/8th full load is 4900 W, then its full-load Cu loss would be .......watt. (a) 5600 (b) 6400 (c) 375 (d) 429 28. The ordinary efficiency of a given transformer is maximum when (a) it runs at half full-load (b) it runs at full-load (c) its Cu loss equals iron loss (d) it runs slightly overload. 29. The output current corresponding to maximum efficiency for a transformer having core loss of 100 W and equivalent resistance referred to secondary of 0.25 $2 is....... ampere. (a) 20 (b) 25 (c) 5 (d) 400 30. The maximum efficiency of a 100-kVA trans- former having iron loss of 900 kW and F.L. Cu loss of 1600 W occurs at....... kVA. (a) 56.3 (b) 133.3 (c) 75 (d) 177.7 27. 1

26. A 200 KVA transformer has an iron loss of 1 kW and full-load Cu loss of 2kW. Its load kVA cor- responding to maximum efficiency is ....... kVA. (a) 100 (b) 141.4 (c) 50 (d) 200 If Cu loss of a transformer at 7/8th full load is 4900 W, then its full-load Cu loss would be .......watt. (a) 5600 (b) 6400 (c) 375 (d) 429 28. The ordinary efficiency of a given transformer is maximum when (a) it runs at half full-load (b) it runs at full-load (c) its Cu loss equals iron loss (d) it runs slightly overload. 29. The output current corresponding to maximum efficiency for a transformer having core loss of 100 W and equivalent resistance referred to secondary of 0.25 $2 is....... ampere. (a) 20 (b) 25 (c) 5 (d) 400 30. The maximum efficiency of a 100-kVA trans- former having iron loss of 900 kW and F.L. Cu loss of 1600 W occurs at....... kVA. (a) 56.3 (b) 133.3 (c) 75 (d) 177.7 27. 1

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 3.7P: Consider a source of voltage v(t)=102sin(2t)V, with an internal resistance of 1800. A transformer...

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Similar questions

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
Consider an ideal transformer with N1=3000andN2=1000 turns. Let winding 1 be connected to a source whose voltage is e1(t)=100(1| t |)volts for 1t1ande1(t)=0 for | t |1 second. A2- farad capacitor is connected across winding 2. Sketch e1(t),e2(t),i1(t),andi2(t) versus time t.
In developing per-unit circuits of systems such as the one shown in Figure 3.10. when moving across a transformer, the voltage base is changed in proportion to the transformer voltage ratings. (a) True (b) False
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A 23/230-kV step-up transformer feeds a three-phase transmission line, which in turn supplies a 150-MVA,0.8 lagging power factor load through a step-down 230/23-kV transformer. The impedance of the line and transformers at 230kVis18+j60. Determine the tap setting for each transformer to maintain the voltage at the load at 23 kV.
For an ideal 2-winding transformer, the ampere-turns of the primary winding, N1I1 is equal to the ampere-turns of the secondary winding, N2I2 (a) True (b) False
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Three single-phase, two-winding transformers, each rated 450MVA,20kV/288.7kV, with leakage reactance Xeq=0.10perunit, are connected to form a three-phase bank. The high-voltage windings are connected in Y with a solidly grounded neutral. Draw the per-unit equivalent circuit if the low-voltage windings are connected (a) in with American standard phase shift or (b) in Y with an open neutral. Use the transformer ratings as base quantities. Winding resistances and exciting current are neglected.
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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.
For developing per-unit equivalent circuits of single-phase three-winding transformer, a common Sbase is selected for all three windings and voltage bases are selected in proportion to the rated voltage of the windings (a) True (b) False