4. 100 kVA, 6800-240 V, 50 Hz single phase step down transformer has the following parameters: RLS=0.0082 RHs=2.62 Rfe-HS=50002 XLs=0.0152 XHs=5.22 Xm,HS=88002 Transformer is delivering 80% of rated load at rated voltage and 0.95 lagging power factor. Determine the following: a) The equivalent impedance of the transformer referred to primary. b) Input impedance of the combined transformer and load. c) Actual input voltage at HV side. d) Input impedance if load is disconnected. e) Exciting current at no load.

4. 100 kVA, 6800-240 V, 50 Hz single phase step down transformer has the following parameters: RLS=0.0082 RHs=2.62 Rfe-HS=50002 XLs=0.0152 XHs=5.22 Xm,HS=88002 Transformer is delivering 80% of rated load at rated voltage and 0.95 lagging power factor. Determine the following: a) The equivalent impedance of the transformer referred to primary. b) Input impedance of the combined transformer and load. c) Actual input voltage at HV side. d) Input impedance if load is disconnected. e) Exciting current at no load.

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 3.63P: A 23/230-kV step-up transformer feeds a three-phase transmission line, which in turn supplies a...

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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.
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.
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Rework Problem 3.14 if the transformer is delivering rated load at rated secondary voltage and at (a) unity power factor, (b) 0.8 power factor leading. Compare the results with those of Problem 3.14. -
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