BEE FREE BEE Bachelor of Electrical Engineering Power Systems and Machines Questions and Answers 2

Question 1

What is the primary purpose of a buck-boost transformer in a power distribution system?

Accepted Answer

To regulate voltage levels within a narrow range

Answer

A buck-boost transformer adjusts voltage up or down by a small percentage to maintain acceptable voltage levels in distribution feeders.

Question 2

In a three-phase synchronous generator, what happens when the field excitation is increased beyond the value needed for unity power factor?

Accepted Answer

The generator supplies reactive power to the grid

Answer

Over-excitation causes the synchronous generator to supply reactive power (VAR) to the grid, appearing as a lagging power factor source.

Question 3

Which type of DC motor is best suited for electric traction applications requiring high starting torque?

Accepted Answer

DC series motor

Answer

The DC series motor provides very high starting torque because its field winding is in series with the armature, so torque increases rapidly with current.

Question 4

What is the swing equation used for in power system stability analysis?

Accepted Answer

Determining the rotor angle dynamics of a synchronous machine after a disturbance

Answer

The swing equation relates the accelerating power to the rotor angle of a synchronous machine, which is fundamental to transient stability studies.

Question 5

In a per-unit system, if a transformer has a per-unit impedance of 0.05 on its own base, what does this indicate about its voltage regulation?

Accepted Answer

Approximately 5% voltage drop at full load under unity power factor

Answer

A per-unit impedance of 0.05 means the transformer drops about 5% of rated voltage at full load and unity power factor.

BEE - Bachelor of Electrical Engineering Practice Test

BEE - Bachelor of Electrical Engineering Practice Test

BEE FREE BEE Bachelor of Electrical Engineering Power Systems and Machines Questions and Answers 2