Question: The usual values of maximum flux densities for distribution transformers using hot rolled silicon steel are______________?

• 1. 0.5 to 0.8 Wb/m2
• 2. 0.8 to 1.0 Wb/m2
• 3. 1.1 to 1.35 Wb/m2
• 4. 1.4 to 1.8 Wb/m2

Question: The flash point of transformer oil should be higher than_______________?

• 1. 40°C
• 2. 60°C
• 3. 80°C
• 4. 104°C

Question: The high voltage winding is usually which of the following type ?

• 1. Cylindrical winding with circular conductors
• 2. Cross-over winding with either circular or small rectangular conductors
• 3. Continuous disc type winding with rectangular conductors
• 4. All of the above types

Question: D.C. windings are____________?

• 1. sometimes 2-layer type
• 2. never 2-layer type
• 3. always 2-layer type
• 4. none of the above

Question: For 275 kV transformers, using cold rolled grain oriented steel, which of the following values of flux density may be used?

• 1. 1.0 Wb/m2
• 2. 1.1 Wb/m2
• 3. 1.3 Wb/m2
• 4. 1.6 Wb/m2

Question: A current density of __________ is ilsed for large power transformers with forced circulation of oil or with water cooling coils?

• 1. 1.5 to 2.5 A/mm2
• 2. 3.5 to 4.5 A/mm2
• 3. 4.0 to 5.0 A/mm2
• 4. 5.4 to 6.2 A/mm2

Question: Which of the following is the basic consideration in the design of insulation ?

• 1. Electrical considerations
• 2. Mechanical considerations
• 3. Thermal considerations
• 4. All of the above

Question: The voltage control in electric supply networks in required on account of which of the following reasons ?

• 1. Adjustment of voltage at consumers premises within statutory limits
• 2. Control of active and reactive power
• 3. Adjustment of short period daily and seasonal voltage variations in accordance with variations of load
• 4. All of the above

Question: Transformers with a capacity of up to __________ have a cooling radiator system with natural cooling?

• 1. 2 MVA
• 2. 5 MVA
• 3. 7.5 MVA
• 4. 10 MVA

Question: The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of the following ?

• 1. Corrugations
• 2. Fins
• 3. Tubes
• 4. All of the above