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#### placide

Joined Oct 1, 2011
22

1) A transformer:100kvA, 50Hz, 600v/230v has been tested as follow:
at no load: V1=6000v, V20=240v, Iο=0.5A, Pο=400w at short circuit :
V1sc=200v, I1sc=16A, P1sc=1500w

a.determine the secondary voltage for the normal secondary current and with
1.cosØ=1
b.the same machine, determine the efficiency for animal current and power factor
0.7 lagging.
c. determine the value of r and x for this calculate the value of relative
voltage drop for a current equal to the half of the nominal current and
a power factor of 0.6 lagging.

2) A 20kvA 8000/480v distribution transformer has the following resistances and
Reactances: Rp=32Ω Rs=0.5Ω
Xp=45Ω Xs=0.6Ω
Rc=250kΩ Xm=30kΩ

The excitation branch impedances are given referred to the high-voltage
Side of the transformer
a.find the equivalent circuit of this transformer referred to the voltage side
b.find the per-unit equivalent circuit of transformer
c.assume that this transformer is supplying rated load at 80v and 0.8pf lagging what is this transformers input voltage
d.what is the transformers efficiency under the condition of part(c)

#### SgtWookie

Joined Jul 17, 2007
22,210
• VoodooMojo

#### Wendy

Joined Mar 24, 2008
22,146