INSTRUMENT
TRANSFORMERS
These
are special type of transformers used for
the
measurement of voltage, current, power and energy.
As
the name suggests, these transformers are used in conjunction
with the relevant instruments such as ,
Ammeters,
Voltmeters, Watt meters and energy meters.
Such
transformers are of two types :
- Current Transformer (or Series Transformer)
- Potential Transformer (or Parallel Transformer)
CUREENT TRANSFORMERS
A
current transformer is an instrument transformer which is
used to measure alternating current of large magnitude by stepping
down by transformer action. The primary winding of CT is connected
in series with the line in which current is to be measured and the
secondary is connected to the ammeter.
Measurement
of current as CT :-
The
primary winding is so connected that the current to be
measured passes through it and the secondary is connected to the
ammeter .
The
function of CT is to step down the current.
POTENTIAL TRANSFORMERS
Potential
transformers are used where the voltage
of an AC circuit exceeds 750V as it is not possible to provide
adequate insulation on measuring instruments for voltage more than
this.
Measurement
of voltage by PT:-
The
primary winding is connected to the voltage side to be
measured and secondary to the voltmeter. The
function of PT is to steps down the voltage to the level of
voltmeter.
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