Insulating materials

Insulating materials


Insulators are materials which offers a very high resistance to the flow of electric currents and a very high voltage (KV or mega voltage ) is needed  to pass a few mA of current in them.

Some important properties of insulating materials .
1. Resistivity
2. Dielectric constant
3. Break down voltage

insulating materials, properties of insulating materials , electrical property of insulating materials
When normal voltage are applied to any insulating materials then it offers high resistance to current flow , but  when voltage exceeds a certain value a rearrangement of atomic structure results in a sudden decrease of resistance of the materials and this stage is called puncture of the insulator.

Properties of insulating materials

It is classified as.

1. Electrical properties
2. Physical properties
3. Thermal properties
4. Chemical properties
5. Mechanical properties

1. Electrical properties

The property of an insulating material due to which it resist the flow of electric current is called insulation resistance. It should be as high as possible for a good insulator.

Insulation resistance may be classified
Volume resistance
Surface resistance

2. Physical properties

This property is most important for insulating material. In physical properties depend on various factor.

  • Specific gravity

This is impotent property of insulating materials because high specific gravity varnishes are easily entered into coils.

  • Viscosity

It is very important for liquid dielectric .for example varnish,

  • Hygroscopicity

The property of absorption of moisture by insulating materials is called hygroscopicity . This affects the insulating property badly.

  • Solubility

In some application, insulating materials are applied only after it is dissolved in some solvent.

3. Thermal properties

Insulating materials should work stably within a specific temperature range eg.certain materials like wax becomes soft at high temperatures so can becomes soft and may melt out of the coils or windings resulting in internal short circuit.

Various thermal properties are

  • Heat resistance 

Insulator materials should be heat resistance
Thermal conductivity
The insulator materials should have good thermal conductivity.

  • Ignitibility or Flash point

This property is also important for selecting oil s for transformer for insulation.

  • Thermal stability or composition 

An insulating material should have thermal stability. They should maintain their insulating properties to a stable value in the operating temperature range.

4. Chemical properties.

Insulating materials should be resistant to chemicals. Their properties do not change due to presence of gases, water, acids and alkalies certain plastics possess this property eg. Plastic have replaced paper insulation in many application because paper being gyroscopic and affected by chemicals.
Various chemicals properties are
Chemical resistance

5.Mechanical properties 

  • Insulating materials should be ductile 
  • Material should be tensile strength 
  • Materials should be good toughness quality.
  • Materials have all good mechanical strength 

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