Each of the following questions consists of two statements, one labelled ‘Assertion (A)’ and the other labelled the ‘Reason (R)’. Examine the two statements carefully and decide if the Assertion (A) and Reason (R) are individually true and if so
Insulating Materials for Cables The insulating materials (dielectrics) used for cables must have low discharge current, low dissipation factor (low loss tangent), and should be chemically stable. The materials generally used are impregnated paper, bituminous compounds, rubber, compressed air, mineral
In electrical machines, the insulation system must withstand the high electrical stresses and severe mechanical stresses induced by the magnetic field of the moving rotor. In machines, multi-turn windings are put in narrow armature slots, which are usually grounded. Rotating
The insulating materials used in power and distribution transformers must possess the following properties: Good electrical properties to withstand the power frequency (50 Hz) voltages and impulse overvoltages. Good mechanical properties to withstand fabrication and handling during manufacture and electromagnetic
Solid insulating materials may be natural organic substances like paper, cloth, rubber, etc. or inorganic materials like Mica, Glass, or synthetic materials like plastics. The different solid insulating materials are: Paper and Pressboards Fibrous materials (unimpregnated and impregnated) Impregnated coating,
An ideal insulating liquid must have following properties: High electric strength, impulse strength, and volume resistivity. Low dielectric dissipation factor. High or low dielectric constant (depending on application). High specific heat and thermal conductivity. Excellent chemical stability and gas-absorbing properties.
Meissner’s Effect The repulsion of magnetic flux from the interior of a piece of superconducting material as the material undergoes to the transition to the superconducting phase is known as Meissner’s Effect. In superconductor B = 0 µo( H +
There are two types of superconductor materials Type-1 superconductor Type-2 superconductor Type-1 superconductor They are also called as Soft Superconductor. Their critical field and transition temperature are low. They exhibit complete Meissner’s and Silsbee rule. The change of state from normal to superconductivity and vice-versa
Semiconductor Materials Types Elemental Semiconductor materials Compound Semiconductor materials Amorphous Semiconductor materials 1. Elemental Semiconductor materials Example: Ge, Si, C, B, Al, Ga, P, As, Sb, Bi, etc. a). Arsenic (As) It is pentavalent semiconductor material. It is used as donor N-type semiconductor material.
Before selecting an insulation system for a particular application, the following properties need to be considered. Mechanical Thermal Environmental including chemical Electric Economic 1. Mechanical properties The mechanical properties considered are the tensile strength, elongation, tensile modulus, compressive modulus, impact