Transformer – Definition, Types, Working Principle, Diagram

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What is a Transformer?

Transformer is a device which:

  1. Transfer Electrical power from one electrical circuit to another Electrical circuit.

  2. It’s working without changing the frequency.

  3. Work through on electric induction.

  4. When, both circuits take effect of mutual induction.

  5. Can’t step up or step down the level of DC voltage or DC Current.

  6. Can step up or step down the level of AC voltage or AC Current.

Construction of a Transformer

Construction of a Transformer
Construction of a Transformer

1

Oil filter valve

17

Oil drain valve

2

Conservator

18

Jacking boss

3

Buchholz relay

19

Stopper

4

Oil filter valve

20

Foundation bolt

5

Pressure-relief vent

21

Grounding terminal

6

High-voltage bushing

22

Skid base

7

Low-voltage bushing

23

Coil

8

Suspension lug

24

Coil pressure plate

9

B C T Terminal

25

Core

10

Tank

26

Terminal box for protective devices

11

De-energized tap changer

27

Rating plate

12

Tap changer handle

28

Dial thermometer

13

Fastener for core and coil

29

Radiator

14

Lifting hook for core and coil

30

Manhole

15

End frame

31

Lifting hook

16

Coil pressure bolt

32

Dial type oil level gauge

Types of Transformers

There are two basic Types of Transformers

  1. Single Phase Transformer

  2. Three Phase Transformer

Below are the more types of transformer derived via different functions and operation etc.

Types of Transformers w.r.t Cores

  • Core Type Transformer

  • Shell Type Transformer

  • Berry Type Transformer

Types of Transformer w.r.t uses

  • Large Power Transformer

  • Distribution Transformer

  • Small Power Transformer

  • Sign Lighting Transformer

  • Control & Signalling Transformer

  • Gaseous Discharge Lamp Transformer

  • Bell Ringing Transformer

  • Instrument Transformer

  • Constant Current Transformer

  • Series Transformer for Street Lighting

Types of Transformer w.r.t Cooling

  • Self Air Cooled or Dry Type Transformer

  • Air Blast-Cooled Dry Type

  • Oil Immersed, Self Cooled (OISC) or ONAN (Oil natural, Air natural)

  • Oil Immersed, Combination of Self Cooled and Air blast (ONAN)

  • Oil Immersed, Water Cooled (OW)

  • Oil Immersed, Forced Oil Cooled

  • Oil Immersed, Combination of Self Cooled and Water Cooled (ONAN+OW)

  • Oil Forced, Air forced Cooled (OFAC)

  • Forced Oil, Water Cooled (FOWC)

  • Forced Oil, Self Cooled (OFAN)

Types of  Instrument Transformer

  • Current Transformer

  • Potential Transformer

  • Constant Current Transformer

  • Rotating Core Transformer or Induction regulator

  • Auto Transformer

Operating & Working Principle of a Transformer

Transformer is a static device (and doesn’t contain on rotating parts, hence no friction losses), which convert electrical power from one circuit to another without changing its frequency. it Step up (or Step down) the level of AC Voltage and Current.

Transformer works on the principle of mutual induction of two coils or Faraday Law’s Of Electromagnetic induction. 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 due to Faraday law’s of electromagnetic induction.

The transformer is based on two principles: first, that an electric current can produce a magnetic field (electromagnetism), and, second that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the current in the primary coil changes the magnetic flux that is developed. The changing magnetic flux induces a voltage in the secondary coil.

A simple transformer has a soft iron or silicon steel core and windings placed on it(iron core). Both the core and the windings are insulated from each other. The winding connected to the main supply is called the primary and the winding connected to the load circuit is called the secondary.

Winding (coil) connected to higher voltage is known as high voltage winding while the winding connected to low voltage is known as low voltage winding. In case of a step up transformer, the primary coil (winding) is the low voltage winding, the number of turns of the windings of the secondary is more than that of the primary. Vice versa for step down transformer

Limitation of the Transformer

To understand the main points, we have to discuss some basic terms related to transformer operation. So lets back to basic for a while.

A transformer is an AC machine that steps up or steps down an alternating voltage or current. A transformer being an AC machine however cannot step up or down a DC voltage or DC current. It sounds a bit weird though. You might be thinking “so are there not DC transformers?”

To answer the two questions whether there are or there are not DC transformers and know “why transformer cannot step up or step down a DC voltage” it’s necessary we know how electric current and magnetic field interact with each other in transformer operation.

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