What Is Dielectric Material ?• A dielectric material is a substance that is a poor

conductor of electricity, but an efficient supporter of electrostatic fields. If the flow of current between opposite electric charge poles is kept to a minimum while the electrostatic lines of flux are not impeded or interrupted, an electrostatic field can store energy. This property is useful in capacitors, especially at radio frequencies. Dielectric materials are also used in the construction of radio-frequency transmission lines.

Some Examples Of Dielectric Material

• In practice, most dielectric materials are solid. Examples include porcelain (ceramic), mica, glass, plastics, and the oxides of various metals. Some liquids and gases can serve as good dielectric materials. Dry air is an excellent dielectric, and is used in variable capacitors and some types of transmission lines. Distilled water is a fair dielectric. A vacuum is an exceptionally efficient dielectric.

Application Of Dielectric Material• Based on various properties like insulation,

temperature dependency, permittivity, dielectric strength, dielectric material are used as various industrial material for manufacturing of electrical devices. Most common uses of these material are in. Capacitor, power Transformer, Cables, Spark generators, transducers, etc..

• In our syllabus we have give application of two dielectric material :-1. Capacitor2. Transformer

Dielectric In Capacitor• There are many dielectric capacitors

available based on their applications. The advantages to use a dielectric materials, it has higher electric storage capacity than air when it is placed between two conducting plates. However, a high permittivity allows a greater charge to be stored at a given voltage.

Applications of Dielectric In Capacitor

• The Major role of dielectric material in capacitor is to store electric energy. Based on the nature of the dielectric material used, the capacitor fall into three groups.

1. Gaseous dielectric in capacitor.2. Liquid dielectric in capacitor.3. Solid dielectric in capacitor.

1. Capacitor with vacuum, air, or other gases as dielectric are used in radio frequency and low frequency measuring circuits.

2. Capacitor with mineral oil as dielectric are used in high voltage applications, where large value of capacitance is required.

3. Capacitor with a combination of solid and liquid dielectric are used in the applications where precision is not so important nut a high value capacitance is required.– In electric power distribution system for

power factor correction, this type of capacitors are used.

–Ex: Glass, mica, oil impregnated paper dielectric, mineral oil, castor oil.

4. Capacitor with only solid dielectric like sodium, glass and titanium oxide are used in laboratory as standard capacitors.

Dielectric in Transformer• We can say that transformer is

basic arrangement of conductors and dielectric insulators.

• We know that transformer contains two parts: Primary coil and secondary coil.

• Energy transforms from primary coil to secondary coil only through magnetic induction, not by any electrical path. So to avoid electrical conduction we must use dielectric insulator at all possible places.

Applications of Dielectric In Transformer

• In transformer, the dielectric material are used as insulator as well as cooling agents. Based on the applications of dielectric in transformer they fall into three groups.

1. Gaseous Dielectric in transformer.2. Liquid dielectric in transformer.3. Solid dielectric in transformer.

Gaseous Dielectric In Transformer• The usage of nitrogen in

transformer prevents oxidation and reduces the rate of deterioration.

• Sulphur hexafluoride dielectric is an electronegative gas which is used in transformer. It is non-toxic, non-inflammable and chemically inert.

Nitrogen filled transformer

SF6 Sulphur Hexafluoride filled transformer

Liquid Dielectric In Transformer• Transformer oil- Its is a class of

mineral insulating oil and is used as a coolant. It also maintains the insulation of the winding.

• Fluorocarbon liquids are used in large transformer to give high heat transfer rates together with high dielectric strength.

Solid Dielectric In Transformer• Fibrous materials are used in air cooled

Transformers.• Cotton tape is used for insulating the

conductors of oil cooled transformers.• High quality synthetic resin bonded

paper in the form of cylinders is used as an insulator between core and coils and also between primary and secondary windings.

• Press board or press paper is used as a filling, and as a packing material between coil.

Solid Insulation Dielectric Transformer Cross section

Solid Insulation Dielectric Transformer