Dielectric loss, Physics

Electrical Properties of Dielectric Material

A loss of energy which eventually produces a rise in temperature of a dielectric placed in an alternating electric field is called "dielectric loss". The dielectric material separates the two electrodes or conductors are stressed when subject to a potential. When the potential is reversed, this change of stress is reversed involves molecular rearrangement with the dielectric. This includes energy loss with every reversal. This is because then the molecules have to overcome a certain amount of internal in the process of alignment. The energy exhausted in the procedure is released as heat in the dielectric. Dielectric losses results from the heating effect on the dielectric material between the conductors. Power from the source is utilized in heating the dielectric. The heat produced is dissipated into the surrounding material. When there is no potential difference between two potential, the atoms in the dielectric material among them are normal and the orbits of the electrons are circular. When there is some potential difference between two conductors, the orbits of the electrons vary. The excessive negative charge on one conductor repels electrons on the electrons dielectric towards the positive conductor and thus distorts the orbit of the electrons. A change in path of electrons requires more energy, introducing a power loss. The atomic structure of rubber is harder to deform then the structure of some other dielectric materials. Such as polythene, distort easily. Therefore polythene easily is often used as a dielectric because less power in consumed when its electrons orbit is distorted. When a perfect insulator is subjected to insulating voltage it is like applying alternating voltage to a perfect capacitor. In such a case there is no consumption of power. Only vacuum and purified gases approach this perfection in such cases the charging current would lead the applied voltage by 90 exactly. This would mean that there is no power loss in the insulation. In most insulating materials that is not the case. There is definite amount of dissipation energy when an insulator is subjected to alternating voltage. It is dissipation of energy that is called dielectric loss. In commercial insulators the leakage current does not lead applied voltage by exactly 90. The phase angle is always less than 90. For an insulator having a voltage V applied to a frequency f Hz the dielectric power loss can be calculated. 

Posted Date: 7/7/2012 5:43:23 AM | Location : United States







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