. Figure 10.Baisc Electrical Installation Work
214
Secondary coil
500 turns
Ns 500
Vp 230V supply 115V output
Primary coil
1000 turns
Np 1000
L
o
a
d
Magnetic flux
2:1 turns ratio
FIGURE 10. The ammeter calibrated take account the turns
ratio the transformer, that the ammeter displays the actual current
being taken the load when the ammeter actually only taking small
proportion the load current.23 shows step transformer where the
primary winding has only half the number turns the secondary wind-
ing.
Definition
Step down Transformers are used to
reduce the output voltage, often for
safety reasons. The turns ratio 1:2 and, therefore, the secondary voltage doubled. The turns
ratio 2:1 and, therefore, the secondary voltage halved. Figure 10.
From the general equation:
V
V
N
N
p
s
p
s
the equation for the secondary turn is:
N
N V
V
N
V
V
s
p s
p
s
∴
800 12
230
42 turns
42 turns are required the secondary winding this transformer give secondary
voltage 12V.
A Current Transformer (or CT) has the large load currents connected to
the primary winding the transformer and the ammeter connected the
secondary winding.
Step Transformers are used increase the output voltage.22 shows step down transformer where the pri-
mary winding has twice many turns the secondary winding. The elec-
tricity generated power station stepped for distribution the
National Grid Network.22
A step down transformer.
Instrument Transformers are used industry and commerce that large
currents and voltage can measured small electrical instruments. The elec-
tricity generated power station
is stepped for distribution the
National Grid Network.
Step Transformers are used to
increase the output voltage.
Key Fact
Transformers
● Transformers are very efficient
(more than 80%) because they do
not have any moving parts.
Types transformer
Step down Transformers are used reduce the output voltage, often for
safety reasons
