309A Transformers and Power Distribution

Question 1

What is the primary function of a distribution transformer in a power system?

Accepted Answer

To step down transmission voltage to utilization voltage levels

Answer

To generate electrical power

Answer

To store electrical energy

Answer

To convert AC to DC

Question 2

What is the turns ratio of a transformer with 2400 primary turns and 240 secondary turns?

Accepted Answer

10:1

Answer

1:10

Answer

5:1

Answer

24:1

Question 3

What type of transformer connection provides both three-phase power and a neutral for single-phase loads?

Accepted Answer

Delta-wye

Answer

Delta-delta

Answer

Wye-delta

Answer

Open delta

Question 4

What is the purpose of transformer oil in a liquid-filled transformer?

Accepted Answer

To provide insulation and cooling

Answer

To lubricate the windings

Answer

To increase the turns ratio

Answer

To filter harmonics

Question 5

A 75 kVA, 480/120 V single-phase transformer has what full-load secondary current?

Accepted Answer

625 A

Answer

156.25 A

Answer

312.5 A

Answer

937.5 A

Question 6

What is the purpose of the tap changer on a transformer?

Accepted Answer

To adjust the output voltage by changing the effective turns ratio

Answer

To change the frequency of the output

Answer

To switch between single-phase and three-phase operation

Answer

To reverse the polarity of the output