1. Balaji engineering college Special transformer
Prepared by:-Hirapara Kajal( )
Sondarva Kajal( )

2. Content Classification of special transformer 1)Current transformer
2)Potential transformer
3)Pulse transformer
4)Audio transformer
5)Grounding transformer s

3. Classification There are 5 type of special transformer,
1)Current transformer
2)Potential transformer
3)Pulse transformer
4)Audio frequency transformer
5)Grounding transformer
In which current transformer and potential transformer are known as instrument transformer

4. Current transformer

5. Introduction
Current transformer is nothing but a coil wound on a toroidal core.
When a large current carried by a conductor is to be measured, it is advisable to avoid the connection of ammeter in this high current circuit
For this purpose a current transformer is used.

6. Construction
C.T has a primary coil of one or more turns, bar act as the primary.
The primary of C.T carries the large current I1 which is to be measured, so it is of large cross sectional area.
The secondary of C.T is made up of large number of turns. it is wound on a core. the secondary winding is a law current winding hence its cross sectional area is small

7. Construction and equivalent circuit

8. Operation
C.T is basically a step up transformer. Hence the secondary is a high voltage law current winding. The current is stepped down.
The secondary current is given by
I2=I1*N1/N2
Where N2>>N1

9. Potential transformer

10. Introduction
The potential transformer is another type of instrument transformer.
It is used to measure high voltage.
The construction of potential transformer is same as that of normal transformer.

11. Description
To measure high voltage, the potential which is step down transformer is connected across high voltage terminals and voltmeter is connected on low voltage side.
The scale of voltmeter is suitably calibrated by taking into account the turns ratio of potential transformer.
The secondary voltage is given by
V2=V1*N2/N1
where , V2 = voltmeter reading

12. Circuit for potential transformer

13. Application of C.T. and P.T.
1)Measurement of current in single phase and 3 phase power system. 2)Measurement of voltage in single phase and 3 phase power system. 3)Measurement of power. 4)Measurement of energy.

14. Pulse transformer

15. Introduction
Pulse transformer is designed to couple pulses from primary to the load connected to the secondary, without changing the shape of the pulse.
Pulse transformer are used for coupling pulses from a low power digital circuit to a high power triac circuit maintaining the isolation between them.

16. Features
1)Pulse transformer are small in size. 2)It has comparatively few number of turns. so the leakage induction of the winding is small. 3)Special type of cores called ferrite cores are used for the construction of pulse transformer. 4)The magnetizing inductance of the pulse transformer is high.

17. Performance
A pulse transformer is supposed to couple the pulse from primary to secondary by preserving the shape.
So the performance of a pulse transformer can be judged by measuring the effect of pulse transformer on the shape of the output pulse.
The pulse transformer performance parameter based on the shape of output waveform.

18. Circuit for pulse transformer

19. Application of pulse transformer
1)In the pulse generating circuits. 2)Control circuits. 3)Radars 4)Microwave tube circuits. 5)As isolation transformers.

20. Audio frequency transformer

21. Introduction
The audio frequency transformer are specifically designed for use in audio circuits.
They operate in the audio frequency range (20Hz to 20kHz)
The construction of A.F. amplifier is same as that of normal transformer. These are iron core transformers.
A.F. transformers were originally designed for connecting different telephones systems to each other keeping their respective power supplies isolated.

22. Functions
1)To block RF interference. 2)To block DC component of an audio signals. 3)To spite or combine audio signals. 4)To provide impedance matching. 5)They can be used as driving transformer.

23. Circuit for audio frequency transformer

24. Application of AF transformer
1)AF amplifiers 2)radio, TV receiver 3)Music system 4)Impedance matching 5)Professional audio systems.

25. Grounding transformer

26. Introduction
Voltage transformer can also be used for grounding transformer.
It acts as a very high reactance earthing device.
The generating circuit is isolated from the main distribution system.
The earth neutral acts as a reflection point for the travelling waves through the machine windings.

27. Circuit for grounding transformer

28. Application of grounding transformer
The application of ground transformer is in generating equipment that are directly connected to step-up transformer.

29. Thank you