Three Phase Systems In Power Applications(Engineering > Electrical Engineering ) Questions and Answers
Question 1. In a Y-connected source feeding a ∆-connected load,
Each phase of the load has one-third of the full line voltage across it
Each phase of the load has two-thirds of the full line voltage across it
Each phase of the load has the full line voltage across it
Each phase of the load has a voltage across it equal to √3
Explanation:-
Answer: Option C. -> Each phase of the load has the full line voltage across it
Question 2. The stator is the rotating assembly in a generator or motor.
True
False
Explanation:-
Answer: Option B. -> False
Question 3. In a Y-connected circuit, between each line voltage and the nearest phase voltage, there is a phase angle of
0°
30°
60°
120°
Explanation:-
Answer: Option B. -> 30°
Question 4. Compare the total copper cross sections in terms of current-carrying capacity for a single-phase and a three-phase 120 V system with effective load resistance of 15 Ω.
Single-phase 32 A; three-phase 16 A
Single-phase 16 A; three-phase 8 A
Single-phase 8 A; three-phase 4 A
Single-phase 16 A; three-phase 0 A
Explanation:-
Answer: Option B. -> Single-phase 16 A; three-phase 8 A
Question 5. An alternator is an electromechanical ac generator.
True
False
Explanation:-
Answer: Option B. -> False
Question 6. In a ∆-connected generator, there is a 120° difference between each line current and the nearest phase current.
True
False
Explanation:-
Answer: Option B. -> False
Question 7. In a Y-connected generator, there is a 120° difference between each line voltage and the nearest phase voltage.
True
False
Explanation:-
Answer: Option B. -> False
Question 8. Power is measured in a three-phase load by using an ammeter.
True
False
Explanation:-
Answer: Option B. -> False
Question 9. A two-phase generator is connected to two 90 Ω load resistors. Each coil generates 120 V ac. A common neutral line exists. How much current flows through the common neutral line?
1.33 A
1.88 A
2.66 A
1.77 A
Explanation:-
Answer: Option D. -> 1.77 A
Question 10. A three-phase generator is connected to three 90 Ω load resistors. Each coil generates 120 V ac. A common neutral line exists. How much current flows through the common neutral line?