Electrical Engineering Materials – APSEEE

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Insulating Materials

Insulating Materials

Insulating materials are the materials that is able to insulate. It prevent the current flows through them. The materials that posses insulating properties is called an insulator. In this article, we will study about classification, Properties, applications of insulating materials.




Classification of insulating Materials

Insulating Materials are divided into three types

  • Solid insulating materials
  • Liquid insulating materials
  • Gaseous insulating materials

Solid Insulating Materials

Solid insulating materials are used to protect the electrical cables and wires.  A layer solid insulating materials deposits on the conductors used in cables or wires. Solid insulating materials are also used to make switch board sheets, switches etc.

Different Types of Solid Insulating Materials

  • Fibrous materials

Examples of Fibrous Materials

wood, paper and card board, insulating textiles etc.

  • Impregnated fibrous materials
  • Non resinous materials

Examples of Non resinous materials

asphalts, bitumens, waxes etc.

  • Ceramics

Examples of Ceramics

porcelain, steatite, titanate, etc.

  • Natural and synthetic rubbers

Examples of Natural and synthetic rubbers

natural rubber, hard rubber, butyl rubber, neoprene, hypalon, silicon rubber etc.

  • Mica

Liquid Insulating Materials

Liquid insulating materials are used in circuit breakers and capacitors. Oil is the example of liquid insulating materials.

Different types of liquid insulating materials

  • Oils
  • Varnishes





Gaseous Insulating Materials

Some gases are also good insulators. These gases are used in circuits breakers and many other devices.

Examples of Gaseous Insulating Materials

Carbon dioxide (CO2), Dry air, nitrogen, etc.

Properties of Insulating Materials

An good insulating materials should have following properties:-

  • Insulating materials should have high resistivity in the order of mega ohm so that, no current flows through it.
  • Insulating materials should have low thermal conductivity.
  • Insulating materials should be chemically inert.
  • Insulating materials should have high dielectric strength at the specified temperature
  • Insulating materials should be such that it does not affected by moisture.

Applications of Insulating Materials

  • Insulator are used transmission line towers.
  • Insulating materials coating is used over the cables and wires.
  • Insulating materials used in all hand held electrical tools to prevent their user from electrical shock hazard.

 

 

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Conducting Materials

Conducting Materials

Conducting materials are those materials which offers easy path to the flow of electric current. It offers low resistance to the flow of current. Silver, Copper, Aluminium, iron are the example of conducting materials. Conducting materials are subdivided into low resistivity and high resistivity materials.

Low Resistivity Materials

There are the materials which offers low resistance to the flow of electric current through them. In order words, we can say that current can easily flow in these materials.

Low resistivity materials are used in house wiring, as conductors for power transmission and distribution of an electric power, in windings of electric machines like transformer, motors and generators. Basically, these materials are used where low power losses and voltage drops are required.

List of low resistivity materials are given below

  • Copper
  • Aluminium
  • Iron

Copper and Aluminium are used commercially because these materials have low resistivity and high conductivity. The conductivity of copper is higher than aluminium but due low cost of aluminium these are used in most of applications. Iron is used basically for manufacturing of earth wire or ground wire. The resistivity of iron is very high as comparatively to copper and aluminium.

Properties of Low Resistivity Materials

  1. It should have low temperature coefficient.
  2. The mechanical strength should be high.
  3. The material should be ductile which allow it to be drawn out into a wire.
  4. These materials should be such that it is not corroded when used in out-door services.

High Resistivity Materials

These materials are used for making resistance elements for heating devices filaments of lamps, rheostats etc. High resistivity materials are used in all such applications where a large value of resistance is required.

Tungsten, Nichrome etc are the examples of high resistivity materials.

Properties of High Resistivity Materials

The high resistivity materials should have following properties.

  1. These materials should have low temperature coefficient of resistance.
  2. These materials should have high meeting point. So it can withstand high temperature for a long time without melting.
  3. It should be able to withstand high temperature for a long time without oxidation.
  4. These materials should be ductile.
  5. High resistivity materials should have high tensile strength.

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