The ratings of a three-phase, three-winding transformer are Primary: Y connected, 66 kV , 15 MVA Secondary: Y connected, 13 . 2 kV , 1 0 MVA Tertiary: Δ connected, 2 . 3 kV , 5 MVA Neglecting resistances and exciting current, the leakage reactances are: X PS =0 .09 per unit on a 15-MVA, 66-kV base X PT =0 .08 per unit on a 15-MVA, 66-kV base X ST =0 .05 per unit on a 10-MVA, 13 .2-kV base Determine the per-unit reactances of the per-phase equivalent circuit using a base of 15 MVA and 66 kV for the primary.
The ratings of a three-phase, three-winding transformer are Primary: Y connected, 66 kV , 15 MVA Secondary: Y connected, 13 . 2 kV , 1 0 MVA Tertiary: Δ connected, 2 . 3 kV , 5 MVA Neglecting resistances and exciting current, the leakage reactances are: X PS =0 .09 per unit on a 15-MVA, 66-kV base X PT =0 .08 per unit on a 15-MVA, 66-kV base X ST =0 .05 per unit on a 10-MVA, 13 .2-kV base Determine the per-unit reactances of the per-phase equivalent circuit using a base of 15 MVA and 66 kV for the primary.
Solution Summary: The author calculates the per unit reactance of the three-phase transformer neglecting winding resistances and excitation current.
In the single-phase, three-
winding, transformer, the
primary current is equal to lo at
the condition of
ints
there is no load on tertiary windings
the current in secondary windings equal
to zero
the resistances (R1, R2, and R3) in
transformer windings are equal
the inductances (L1, L2, and L3) in
transformer windings are equal.
A single-phase transformer has a voltage ratio on open circuit of 7900/660 V. The
primary and secondary resistances are 0.55 ohm and 0.035 ohm respectively.
The corresponding leakage reactances being 4.22 ohm and 0.18 ohm. The load is
equivalent to a coil of resistance 3.85 ohm and inductive reactance of 4.2 ohm.
Determine the terminal voltage of the transformer and the output in kW when
supplying a given load using approximate equivalent circuit when the applied
voltage is 7912 V.
Your answer
Chapter 3 Solutions
Power System Analysis and Design (MindTap Course List)
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How does a Transformer work - Working Principle electrical engineering; Author: The Engineering Mindset;https://www.youtube.com/watch?v=UchitHGF4n8;License: Standard Youtube License