NIET ALWAR Avdhesh kumar

1. Presentation
on
Instruments Transformers
ByAvdhesh kumar meena
B.Tech 4th Year Electrical Branch
NIET Alwar Rajasthan
avdheshkumarmeena10@gmail.com

3. What is Transformer ??
A transformer is a static device
which is use to convert high
alternatic voltage to a low
alternatic voltage and vice versa,
keeping the frequency same

4. Principle Of Operation
Transformer works on the
principle of mutual induction of
two coils.
When current in the primary coil is
changed the flux linked to the
secondary coil also changes.
Consequently an EMF is induced
in the secondary coil.

6. What is Induction law ??
Faraday’s law states that:
Vs=Ns.dΦ/dt
where
Vs is the instantaneous secondry
winding voltage.
Ns is the number of turns in the
secondary coil.

7. Construction of Transformer
Mainly Transformers have two types
of construction….
CORE type construction
SHELL type construction

8. Core type Transformer
In the Core type the primary and
secondary windings are placed
on each side of the core.
The core type has two limbs

10. Shell type Transformer
In Shell type transformers the LV
& HV windings are sandwiched
between each other.
The shell type has three limbs.

12. Types of Transformer
Step UP Transformer :
A transformer in which Ns>Np is called a step up
transformer. A step up transformer is a transformer
which converts low alternatic voltage to high
alternatic voltage.
Step DOWN Transformer :
A transformer in which Np>Ns is called a step
down transformer. A step down transformer is a
transformer which converts high alternatic voltage
to low alternatic voltage.

13. A wide variety of transformer
designs are used for different
applications.
 Auto-transformer
 Poly-phase transormer
 Leakage transformer
 Resonant transformer
 Instrument transformer

14. AUTO-TRANSFORMERS
Autotransformer is a one winding
transformer in which a part of the
winding is common to both HV & LV
sides

15. POLY-PHASE
TRANSFORMER
Three separate single phase transformers
are suitably connected for 3 phase
operation.
A single three phase transformer in which
the cores and windings for all the three
phases are combined in a single structure.

17. INSTRUMENT
TRANSFORMERS
Instrument transformers are necessary for
 Isolating the protection, control &
measurement equipment from the high
voltages of a power system
 Supplying the equipment with the
appropriate values of current and voltage

18. Types of Instrument
Transformers
Two Types of Instrument X-formers
 Current Transformer (CT)
 Potential Transformer (PT)

19. Current Transformer
Construction

21. Lay
er
2 Lay
er
1
Co
re

23. Point to note about CT
 Primary current depends on load, but not
on the burden
 Current coil of Wattmeter or Ammeter is
connected across the terminal of the
secondary or Relay
 Secondary operates near short circuit
conditions
 One of the terminal of CT secondary
winding is earthed

24. Types of CT

25. Care, while operating with CT

26. Connections of CT and PT

27. Potential Transformer
 Potential transformer normally
known as PT.
 That is a type of step down
transformer.
 Step down transformer ,step down
the voltage and rise the current.
 The voltage is step down in the
known ratio called voltage ratio.

28. Principle of operation PT
 It is always connected in parallel to the
transmission line.
 It’s secondary winding is very low with respect to
the primary.
 The secondary winding is designed so that a
voltage of 100 to 150 v is delivered to the
instrument load.
 Line voltage =voltmeter reading/Ratio
Ratio=no. of turn in secondary/no.of turn
in primary

31. construction of potential
transformer
 Core size is large and made of by
steel.
 Primary side large no. of turn.
 Secondary side only few no. of
turn.
 Secondary and primary winding
are insulated to each other and
oil immersed.

32. Conclusion
Current Transformer
 Measuring current
Monitoring the operation of the power grid
Potential Transformer
Measuring Voltage
Provides isolation from high voltages

33. Thank