Question

**A single phase 3kVA 480/240 V 50 Hz transformer has the
following parameters:**

**High** **voltage side: r1 = 0.25 Ω Xl1 =
0.75**

**Low** **voltage side: r2 = 0.05 Ω Xl2 =
0.18**

**a) Draw** **the equivalent circuit with
quantities referred to the low voltage side;**

**b) Determine the voltage regulation when the transformer
is supplying full load at 240** **Vrms**
**and 0.9 power factor lagging;**

**c) If the load terminals are accidentally
short-circuited determine the currents in the high voltage and low
voltage windings.**

**Neglect core losses**

Answer #1

A single phase transformer rated at
3000 KVA, 69kV, 60 Hz has a total internal impedance Zp of 127ohm,
referred to the primary side.
Calculate:
a) primary and secondary
currents
b) voltage regulation from no load to
full load for 2000 kW resistive load, knowing that the primary
voltage supply is fixed at 69 kV.
c) primary and secondary currents if
the secondary is accidentally short circuited.

A 2.2 KVA, 440---220 V, 60 Hz, step-down transformer has the
following parameters: Rp= 3.0 Ω, Xp= 4.0 Ω, Rs= 2.5 Ω, Xs= 2.0 Ω,
Rc= 60 KΩ, and Xm = 15 KΩ. The transformer is operating at full
load with a power factor of 0.707 lagging. The magnetizing branch
impedance can be ignored.
a) Draw the transformer’s equivalent T-circuit,
b) Find the equivalent winding impedance referred to the high
side,
c) Calculate the primary and secondary currents,
d) Determine...

A 2.2 KVA, 440---220 V, 60 Hz, step-down transformer has the
following parameters: Rp= 3.0 Ω, Xp= 4.0 Ω, Rs= 2.5 Ω, Xs= 2.0 Ω,
Rc= 60 KΩ, and Xm = 15 KΩ. The transformer is operating at full
load with a power factor of 0.707 lagging. The magnetizing branch
impedance can be ignored.
a) Draw the transformer’s equivalent T-circuit,
b) Find the equivalent winding impedance referred to the high
side,
c) Calculate the primary and secondary currents,
d) Determine...

Three 1-φ, 100 kVA, 1730/208 V, 60 Hz transformer are connected
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ohms. The transformer delivers 40 kW to the load at 0.8 p.f.
leading.
a) Determine the phase and the line currents at the primary and
the secondary sides.
b) Draw the equivalent per-phase circuit refereed to the primary
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and the voltage rating of 345kV wye /34.5kV delta with a leakage
reactance of 12% and transformer connection is wye-delta. Select a
base of 20 MVA and 345 kV on the high-voltage side. Please
determine the following:
(a) Turn ratio of windings
(b) Transformer reactance referred to low-voltage side in ohms
(c) Transformer reactance referred to low-voltage side in per
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Use MATLAB:
A three-phase Y-A transformer is rated 225-kV:24-kV, 400 MVA and
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terminals. The transformer is supplying a load of 375 MVA, with
0.89 power factor lagging at a voltage of 24 kV (line-to-line) on
its low-voltage side. It is supplied from a feeder whose impedance
is 0.17 + j 2.2 Ohms connected to its high-voltage terminals. The
total load in the system remains constant at 375 MVA....

A 525 V to 110 V, 50 Hz, single phase transformer has
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sketch the phasor diagram representing this
situation. (10) 3.2...

A 10-kVA, 250 / 100-V, 50-Hz single-phase transformer gave the
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Open circuit test: 250 V, 2.6 A, power factor: 0.3 on HV
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Short circuit test: 18 V, 80 A, input power: 240 W on HV
side.
Calculate the following:
4.1 The equivalent circuit parameters of the transformer. (6)
4.2 The efficiency at full load unity power factor. (NB the test
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A 20 kVA single phase transformer
4800/480V has primary resistance and reactance of 5Ω and 15Ω
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(i) The parameter referred to primary
side of transformer and draw the equivalent circuit
(ii) The approximate value of
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a) A three phase transformer rated at 30 MVA 10 kV(Δ)/1 kV(Y) is
supplying a load at the low voltage side. The load absorbs 5 MVA,
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system. Find the Line to Line voltage at the primary side of the
transformer.
b) A three-phase synchronous generator...

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