Radiator is a bank of hollow pipe line which is used to transfer the thermal energy from one medium to another for the purpose of cooling. Some Bank are used at the power transformer for cooling the transformer oil as well as reduces the winding temperature under loading condition. The radiators are connected to the transformer through pipe line at upper and lower side of the transformer which is shown in fig.
When the transformer is under loading condition, the transformer will be heated enormously and that heat has to be reduced under limited value otherwise the transformer may me damaged due over heating. We can easily reduce the temperature of the transformer by applying radiator bank.Now , we describe how it is reduce the temperature of transformer oil . As per convection heat transfer law, warm oil increases in volume and comes to the upper portion of the main tank and this heated oil enters in the radiator through top valve and cools down by dissipating heat through the thin radiator wall. This cold oil comes back to the main tank through the bottom valve. This cycle is repeated continuously till the load is connected to the transformer. Dissipation of heat radiator can be get faster by force air provided by means of fans. At higher ratting transformer( i.e <= 50 MVA Tr.), an oil pump may be used for speeding up oil circulation.
Multiple Choice Question (MCQ) of Electronics page-17:241. Which of the following statement is true? a) The saturation voltage VCF of silicon transistor is more than germanium transistor. b) The saturation voltage VCE for germanium transistor is more than silicon transistor. c) The saturation voltage VCE for silicon transistor is same as that for germanium. d) The saturation voltage VCE for silicon transistor is lower than germanium transistor.
Multiple Choice Question (MCQ) of Electronics page-16:226. Which of the following statement is correct? a) Inner electrons are always present in the semiconductor. b) Bound electrons are always present in the semiconductor. c) Free electrons are always present in the semiconductor. d) Inner and bound electrons are always present in the semiconductor.
Multiple Choice Question (MCQ) of Electronics page-15:211. The materials whose electrical conductivity is usually less than 1 × 106 mho/m are a) Semiconductors b) Conductors c) Insulators d) Alloys
Multiple Choice Question (MCQ) of Electronics page-14:196. In which of the following device the base resistors are not added in the package but added externally? a) UJT b) CUJT c) PUT d) None of the above
Multiple Choice Question (MCQ) of Electronics page-13:181. The conduction in JEFT is always by the a) Majority carriers b) Minority carriers c) Holes d) Electrons e) Holes and electrons simultaneously