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