Transformer

A transformer is an electrical device that takes electricity of one voltage and changes it into another voltage.

Types of transformer:

Ø  Step up

Ø  Step down

Ø  Isolating

Ø  Variable etc.

In Ashuganj power station, step up transformers are used to up the voltage and minimize transmission loss.

Step up transformer:

            The transformer in which voltage is increased is called step up transformer. Here the secondary has more turns than the primary winding.

                                 

                                                    Figure: Transformer

Main parts of transformer:                        

Ø  Transformer shell

Ø  Inner core

Ø  Oil reservoir

Ø  Cooling system

Ø  Bushing

Transformer shell:

It is a shell generally made of cast iron or steel. It holds all the equipments inside of shell. In this sense it is an outer casing of transformer.

Inner core:    

Inner core means the main core of parallel plates arranged into the transformer shell. There are two types of windings, primary and secondary.

                        

Figure: transformer core and windings.

Oil reservoir:

            It is a reservoir which keeps the oil reserved for cooling of transformer.

Cooling system:

            In cooling system, oil is used to cool the inner core of transformer by absorbing internal heat. Then this oil is cooled by circulating air. In air cooling system, there are fans and radiators to cool the hot oil. Oil flow through the radiators and air is blown across the radiators to cool the oil. Then the cooled oil is returned to transformer oil reservoir.

Bushing:

            Bushings are insulated bars or wires that connected the transformer with other electrical equipments. It is usually filled with oil to provide extra insulation. To prevent faults, non-conducting gaskets are used with the bushing of transformer.

Other types of transformer:

Current transformer:

A current transformer is designed to provide a current in its secondary which is accurately proportional to the current flowing in its primary. Current transformers are commonly used in electricity meters to facilitate the measurement of large currents which would be difficult to measure more directly. Care must be taken that the secondary of a current transformer is not disconnected from its load while current is flowing in the primary as in this circumstance a very high voltage would be produced across the secondary. Current transformers are often constructed with a single primary turn either as an insulated cable passing through a toroidal core, or else as a bar to which circuit conductors is connected.

Potential transformer:

Voltage transformers are also known as potential transformers. They are used in the electricity supply industry to measure accurately the voltage being supplied. They are designed to present negligible load to the voltage being measured.

Pulse transformers:

A pulse transformer is a transformer that is optimized for transmitting rectangular electrical pulses (that is, pulses with fast rise and fall times and constant amplitude). Small versions called signal types are used in digital logic and telecommunications circuits, often for matching logic drivers to transmission lines. Medium-sized power versions are used in power-control circuits such as camera flash controllers. Larger power versions are used in the electrical power distribution industry to interface low-voltage control circuitry to the high-voltage gates of power semiconductors such as TRIACs, IGBTs, thyristors and MOSFETs. Special high voltage pulse transformers are also used to generate high power pulses for radar, particle accelerators, or other pulsed power applications.

Losses of transformer:

Ø  Winding resistance

Ø  Eddy current

Ø  Stray losses

Ø  Hysteresis losses

Ø  Mechanical losses

Ø  Magnetostriction

Ø  Cooling system

Use of transformer:

1.  Electric power transmission over long distances

2.  High-voltage direct-current HVDC power transmission systems

3.  Large, specially constructed power transformers are used for electric arc furnaces

     in steelmaking.

4.  Rotating transformers are designed so that one winding turns while the other remains stationary. A common use was the video head system as used in VHS and Beta video tape players. These can pass power or radio signals from a stationary mounting to a rotating mechanism, or radar antenna.

Protection of transformer:

            Protection should be taken for efficient operation. To take protection, relay is used. Relay is such a thing which gives electric signal to circuit breaker to open the circuits as required. Such as-

Ø  Protection relay

Ø  Earth fault relay

Ø  Transformer differential relay

Ø  Over current relay etc.

Image Source:  wikipedia

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