DEA temperature Rise in transformer and Estimation of no load

Which of the following factors affects the temperature rise in a transformer?

• A. Ambient temperature

• B. Size of the transformer

• C. Operating voltage

• D. All of the above

What is the thermal resistance of a transformer?

• A. The ratio of the temperature rise to the ambient temperature

• B. The ratio of the ambient temperature to the temperature rise

• C. The ratio of the temperature rise to the power loss

• D. The ratio of the power loss to the temperature rise

Which of the following materials is commonly used as insulation in transformers?

• A. PVC

• B. Rubber

• C. Paper

• D. Glass

Which of the following cooling methods is commonly used in transformers?

• A. Natural air cooling

• B. Forced air cooling

• C. Oil cooling

• D. All of the above

Which of the following factors affects the hot-spot temperature in a transformer?

• A. Ambient temperature

• B. Load current

• C. Insulation

• D. All of the above

What is the relationship between the no-load current and the applied voltage in a transformer?

• A. Directly proportional

• B. Inversely proportional

• C. No relationship

• D. Cannot be determined

What is the no-load current in a transformer?

• A. The current that flows through the primary winding when the secondary circuit is open.

• B. The current that flows through the secondary winding when the primary circuit is open.

• C. The current that flows through the primary winding when the secondary circuit is closed.

• D. The current that flows through the secondary winding when the primary circuit is closed.

What is the significance of estimating the no-load current in a transformer?

• A. It helps to determine the efficiency of the transformer.

• B. It helps to determine the voltage regulation of the transformer.

• C. It helps to determine the power factor of the transformer.

• D. It helps to determine the winding resistance of the transformer.

What is the effect of increasing the core flux density on the no-load current of a transformer?

• A. It increases the no-load current.

• B. It decreases the no-load current.

• C. It has no effect on the no-load current.

• D. It depends on the type of transformer.

What is the estimated no-load current of a transformer with a rating of 100 kVA, a voltage of 220/11 kV, and an impedance of 2%?

• A. 1.58 A

• B. 3.16 A

• C. 6.32 A

• D. 9.48 A