For a cascaded transformer with 2 stages, an impedance test is performed for each stage. Suppose that the results were identical for both stages and were as follow: Xps which is the impedance measured at the primary after shorting the secondary terminals is 1.9 2. Xpt which is the impedance measured at the primary after shorting the tertiary terminals is 1.8 2. Xst which is the impedance measured at the secondary after shorting the tertiary terminals is 1.1 0. For simplicity, assume all turns ratios to be 1:1. Assuming lossless transformer, the resultant reactance representing the whole system will be:

For a cascaded transformer with 2 stages, an impedance test is performed for each stage. Suppose that the results were identical for both stages and were as follow: Xps which is the impedance measured at the primary after shorting the secondary terminals is 1.9 2. Xpt which is the impedance measured at the primary after shorting the tertiary terminals is 1.8 2. Xst which is the impedance measured at the secondary after shorting the tertiary terminals is 1.1 0. For simplicity, assume all turns ratios to be 1:1. Assuming lossless transformer, the resultant reactance representing the whole system will be:

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 3.5MCQ: For an ideal 2-winding transformer, an impedance Z2 connected across winding 2 (secondary) is...

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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
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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