2nd Class Power Engineering 2B3 Practice Exam Part1

2ND CLASS POWER

ENGINEERING 2B3

PRACTICE EXAM PART1

Question 1: What is the primary function of a reverse power relay in a generator system?

Choices:

1) To prevent the generator from running as a motor 2) To protect against overvoltage 3) To synchronize the generator 4) To increase the power factor

Correct Answer: To prevent the generator from running as a motor

Explanation: A reverse power relay trips the generator breaker if power �ows back into the generator, preventing it from motoring.Page 1

Question 2: Which type of AC motor provides the highest starting torque?

Choices:

1) Wound rotor induction motor 2) Squirrel cage induction motor 3) Synchronous motor 4) Split-phase motor

Correct Answer: Wound rotor induction motor

Explanation: Wound rotor induction motors allow external resistance to be added to the rotor circuit, providing very high starting torque.

Question 3: In a three-phase AC system, the phase voltages are separated by an

angle of:

Choices:

1) 90 degrees 2) 120 degrees 3) 180 degrees 4) 360 degrees

Correct Answer: 120 degrees

Explanation: Three-phase power consists of three voltage waveforms that are 120 electrical degrees apart.Page 2

Question 4: What is the e�ect of a low power factor on an electrical system?

Choices:

1) Increased current for the same real power 2) Decreased line losses 3) Higher operating voltage 4) Improved generator e�ciency

Correct Answer: Increased current for the same real power

Explanation: A low power factor means more reactive power is drawn, increasing total current and line losses for the same real power.Question 5: Which device is typically used to correct a lagging power factor in an industrial plant?

Choices:

1) Synchronous condenser or capacitor bank 2) Induction regulator 3) Variable frequency drive 4) Auto-transformer

Correct Answer: Synchronous condenser or capacitor bank

Explanation: Capacitor banks and synchronous condensers supply reactive power, correcting lagging power factor caused by inductive loads.Page 3