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This lecture series is from Electrical Engineering courses. A collection of lectures on all the important topics in EE. These slides covers points such as: Instrument Transformer, Uses of Instrument Transformer, Instrument Transformer as Ct, Advantages, Current Transformers, Core Type, Phasor Diagram, Ratio Error, Types of Current Transformers, Potential Transformer
Typology: Slides
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of
instrument
transformer
transformer
type
current
transformer
type
current
transformer
of
an
instrument
transformer
diagram
These are special type of transformers used for
the measurement of voltage, current, powerand
energy.
As
the
name
suggests,
these
transformers are used in conjunction with therelevant
instruments
such
as
ammeters,
voltmeters, watt meters and energy meters.
Such transformers are of two types :1. Current Transformer (or Series Transformer)2.
Potential Transformer (or Parallel Transformer)
Current transformers are used when the magnitude
of AC currents exceeds the safe value of currentof measuring instruments.
Potential transformers are used where the voltage
of an AC circuit exceeds 750 V as it is notpossible
to
provide
adequate
insulation
on
measuring instruments for voltage more thanthis.
Measurement of current as CTThe primary winding is so connected that the
current to be measured passes through it andthe secondary is connected to the ammeter. The function of CT is to step down the current.
away
from
the
high
voltage
side
by
connecting
long
wires
to
the
instrument
transformer.
This
ensures
the
safety
of
instruments as well as the operator.
extend the range of measuring instrumentslike ammeters and voltmeters.
The
only
main
draw
back
is
that
these
instruments can not be used in DC circuits.
In order to minimise the exciting ampere turns
required, the core must have a low reluctanceand small iron losses. The following three types of core constructions
are generally employed :
In shell type, the windings are placed at thecentral limb, thus it gives better protection tothe windings.
Ring
type
core
is
commonly
used
when
primary
current
is
large.
The
secondary
winding is distributed round the ring and theprimary winding is a single bar.
-^
It is a joint less core and there is very smallleakage reactance.