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Large transformers, when used for some t...

Large transformers, when used for some time, become hot and are cooled by circulating oil. The heating of transformer is due to

A

Heating effect of current alone

B

Hysteresis loss alone

C

Eddy currents losses alone

D

All of above

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The correct Answer is:
d
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After using for some time, big transformers get heated up. This is due to the fact that 1. the current produces heat in transformers 2. occurs in the hysteresis loss transformers 3. liquid used for cooling gets heated Select the correct answer using the code given below.

Read the following text and answer the following questions on the basis of the same: At power plant, a transformer increases the voltage of generated power by thousands of volts so that it can be sent of long distances through high-voltage transmission power lines. Transmission lines are bundles of wires that carry electric power from power plants to distant substations. At substations, transformers lower the voltage of incoming power to make it acceptable for high volume delivery to nearby end-users. Electricity is sent at extremely high voltage because it limits so-called line losses. Very good conductors of electricity also offer some resistance and this resistance becomes considerable over long distances causing considerable loss. At generating station, normally voltage is stepped up to around thousands of volts. Power losses increase with the square of current. Therefore, keeping voltage high current becomes low and the loss is minimized. Another option of minimizing loss is the use of wires of super-conducting material. Super-conducting materials are capable of conducting without resistance, they must be kept extremely cold, nearly absolute zero, and this requirement makes standard super-conducting materials impractical to use. However, recent advances in super-conducting materials have decreased cooling requirement. In Germany recently 1 km super-conducting cable have been installed connecting the generating station and the destination. It has eliminated the line loss and the cable is capable of sending five times more electricity than conventional cable. Using super-conducting cables Germany has also get rid of the need of costly transformers. Transformers generate waste heat when they are in operation and oil is the coolant of choice. It transfers the heat through convection to the transformer housing, which has cooling fins or radiators similar to heat exchangers on the outside. Flush point is a very important parameter of transformer oil. Flashpoint of an oil is the temperature at which the oil ignites spontaneously. This must be as high as possible (not less than 160^(@)C from the point of safety). Fire point is the temperature at which the oil flashes and continuously burns. This must be very high for the chosen oil (not less than 200^(@)C ). Flush point of an oil is

Read the following text and answer the following questions on the basis of the same: At power plant, a transformer increases the voltage of generated power by thousands of volts so that it can be sent of long distances through high-voltage transmission power lines. Transmission lines are bundles of wires that carry electric power from power plants to distant substations. At substations, transformers lower the voltage of incoming power to make it acceptable for high volume delivery to nearby end-users. Electricity is sent at extremely high voltage because it limits so-called line losses. Very good conductors of electricity also offer some resistance and this resistance becomes considerable over long distances causing considerable loss. At generating station, normally voltage is stepped up to around thousands of volts. Power losses increase with the square of current. Therefore, keeping voltage high current becomes low and the loss is minimized. Another option of minimizing loss is the use of wires of super-conducting material. Super-conducting materials are capable of conducting without resistance, they must be kept extremely cold, nearly absolute zero, and this requirement makes standard super-conducting materials impractical to use. However, recent advances in super-conducting materials have decreased cooling requirement. In Germany recently 1 km super-conducting cable have been installed connecting the generating station and the destination. It has eliminated the line loss and the cable is capable of sending five times more electricity than conventional cable. Using super-conducting cables Germany has also get rid of the need of costly transformers. Transformers generate waste heat when they are in operation and oil is the coolant of choice. It transfers the heat through convection to the transformer housing, which has cooling fins or radiators similar to heat exchangers on the outside. Flush point is a very important parameter of transformer oil. Flashpoint of an oil is the temperature at which the oil ignites spontaneously. This must be as high as possible (not less than 160^(@)C from the point of safety). Fire point is the temperature at which the oil flashes and continuously burns. This must be very high for the chosen oil (not less than 200^(@)C ). Oil transfers heat from transformer winding by the process of:

MOTION-ELECTRO MAGNETIC INDUCTION-EXERCISE-2 (Objective problems (Analytical questions))
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  11. Transformer is used to

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  12. Large transformers, when used for some time, become hot and are cooled...

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  13. For same rating which have the maximum efficiency from following :-

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  14. 2.2 किलोवाट शक्ति को 20 ओम वाली लाइन से 44000 वोल्ट पर संचारित किया जा...

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  15. If a transformer have turn tatio 5, frequency 50 Hz root mean square v...

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  16. plane of eddy currents make an angle with the plane of magnetic lines ...

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  17. Eddy currents do not produce

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  18. When a metallic sphere is moved in a magnetic field , it gets heated d...

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