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What is a Transformer???Transformer is a device that increases ordecreases the voltage of alternating current.It works on the principle of electromagnetic induction.

Transformer

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Transformer consist of iron core, Primary coil and secondary coil

Primary coil

Secondary coilIron core

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Primary coil

Iron core Secondary coilSoft iron

Varnish

A transformer’s core consists of thin sheets of iron soft iron insulated from each other by either paint or varnish.This is why it is called a laminated (berlapis) core.

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Laminated core

Soft iron

Laminated

A magnetic substance is required to make the core of a transformer. The material should get easily magnetised and demagnetised. Soft iron serves the purpose best. Hardened iron or steel is unstable as if gets permanently magnetised.

Why is soft iron used to make the core of a transformer?

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Primary coil of transformer

Primary coil

Laminated core

Secondary coilIron core

The primary coil of a transformer is a coil of insulated cooper wire wound on the arm of the laminated core. The ends of the primary coil are connected to an alternating current power source.

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Secondary coil of transformer

Iron core Secondary coil

Primary coil

Insulated wire

The secondary coil is another coil of insulated cooper wire wound around on the laminated core.The output voltage is obtained across the ends of the secondary coils.

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The basic symbol for transformer

Iron core

Secondary coilPrimary coil

Transformer

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A simple Transformer

When the primary coil of a transformer is connected to an AC supply a current flows in the secondary coil of the transformer,

as shown by the multimeter

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The working principle of transformer: The relationship between voltage

across the primary coil and the secondary coil is as follows:

Vp = Np Vs Ns

Np = Number of turns in the primary coil.Ns = Number of turns in the secondary coilVp= voltage of the primary coil.Vs = Voltage of the secondary coil.

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1.Step-up transformer

2.Step-down transformer

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If Ns > Np, then Vs (output voltage) > Np (input voltage).A step-up transformer provides a higher output voltage

for a lower input voltage.

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If Np > Ns, then Vp (input voltage) > Ns (output voltage).A step-down transformer provides lower output voltage

for a higher input voltage.

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Similarities

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Differences

The output current is lower than the input current

The output current is higher than the input current.

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A step-down transformer is used in:a.Electric bellsb.Radioc.Power sub stations

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Transformer are used to step-up or step-down voltage in a transmission system, at specific points.

This enables convenient and safe supply of electricity.

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The output voltage at a power generating station is 11 kV.

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1. The power supply from the generating station is stepped up by a step-up transformer from 11kV to 132kV.2. Then it will be sent to the switch field area for distribution across the national grid.3. This is done to reduce transmission losses.

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The power from the national grid is stepped down by a step-down transformer to 33kV of 11kV before being sent to the industrial estates.

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The power from the national grid is stepped down by a step-down transformer to 415kV or 240 V before being sent to the commercial and residential areas in a city.Thus, transformers help in the distribution of electricity as per the user’s requirement.

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2. Enable efficient and sate distribution of electricity as per the user’s requirement.

Transformer in the Electrical Energy Transmission System help to:

1. Reduce power loss during transmission and distribution

by stepping up voltage for transmission.

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1.A transformer - increase or decreases the voltage of an alternating current (AC) supply.

2.A transformer consists of three parts: i. a primary coil ii. a secondary coil iii. a laminated soft iron core.

3.A step-up transformer - change low voltage to high voltage of the same frequency.

SUMMARY

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4. In a step-up transformer , the number of turns in the primary coil is less then the number of turns in the secondary coil,

thus Np < Ns.

5. A STEP-DOWN transformer - change high voltage to low voltage of the same frequency.

6. In a step-down transformer , the number of turns in

the primary coil is more then the number of turns in the secondary coil, thus Np > Ns.

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