Definition, Formula, Circuit, Waveform diagram, Factors affecting
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
When a dielectric is applied with AC voltage, the electrical energy is absorbed by the dielectric and certain quantity of electrical energy is dissipated in the form of heat energy.
Dielectric Materials
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
Let N be the number of molecules per unit volume and a be the molecular polarisability.
Lorentz field
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
When a dielectric material is placed in an externa electrical field, it produces an induced dipole moment.
Types and their frequency ranges, Comparison
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
The relaxation time tr is s measure of the time scale of polarisation process. It is the time taken for a polarisation process to reach 0.63 of the maximum value of polarization
Langevin Debye equation
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
Since the space - charge polarisation is very small and it is neglegible.
Polarization mechanisms in dielectrics
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
This polarisation occurs due to the accumulation of charges at at the electrodes or at the interfaces of multiphase dielectric materials (two or more phases).
Polarization mechanisms in dielectrics
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
Orientational polarisation takes place only in polar dielectrics. Polar dielectrics have molecules with permanent dipole moments even in the absence of an electrical field as shown in fig. 1.7.
Polarization mechanisms in dielectrics
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
Ionic polarisation is due to the displacement of cations (positive ions) and anions (negative ions) in opposite directions.
Calculation | Polarization mechanisms in dielectrics
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
Electronic polarisation is due to the displacement of positively - charged nucleus and negatively – charged electrons of an atom in opposite directions on the application of an electrical field. This induces dipole moment in the dielectric.
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
Dielectric polarisation occurs due to several microscopic mechanisms. In electric field, the macroscopic polarisation vector is created by the following four microscopic polarisation mechanisms.
Dielectric Materials and Insulation
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
It is defined as the average dipole moment per unit volume of a dielectric
Definition, Formula
Subject and UNIT: Physics for Electrical Engineering: Unit I: Dielectric Materials and Insulation
The electrical behaviour of a dielectric material can be changed by the application of an external electrical field.