MCQ on Three-Phase Systems in Power Applications - Set 01

Practice Test: Question Set - 01


1. Polyphase generators produce simultaneous multiple sinusoidal voltages that are separated by
    (A) Certain constant phase angles
    (B) Certain constant frequencies
    (C) Certain constant voltages
    (D) Certain constant currents

2. In a Y-connected source feeding a ∆-connected load,
    (A) Each phase of the load has one-third of the full line voltage across it
    (B) Each phase of the load has two-thirds of the full line voltage across it
    (C) Each phase of the load has the full line voltage across it
    (D) Each phase of the load has a voltage across it equal to √3

3. 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?
    (A) 1.33 A
    (B) 1.88 A
    (C) 2.66 A
    (D) 1.77 A

4. In a ∆-connected source feeding a Y-connected load
    (A) Each phase voltage equals the difference of the corresponding load voltages
    (B) Each phase voltage equals the corresponding load voltage
    (C) Each phase voltage is one-third the corresponding load voltage
    (D) Each phase voltage is 60° out of phase with the corresponding load voltage

5. In a Y-connected generator, there is a 120° difference between each line voltage and the nearest phase voltage.
    (A) True
    (B) False

6. A simple two-phase generator consists of two conductive loops separated by 90°, rotating in a magnetic field.
    (A) True
    (B) False

7. 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.
    (A) Single-phase 32 A; three-phase 16 A
    (B) Single-phase 16 A; three-phase 8 A
    (C) Single-phase 8 A; three-phase 4 A
    (D) Single-phase 16 A; three-phase 0 A

8. A three-phase ∆-connected generator is driving a balanced load such that each phase current is 12 A in magnitude. When I θa = 12 30° A, what are the polar expressions for the other phase currents?
    (A) I θb = 12 ∠150° A, I θc = 12 ∠-90° A
    (B) I θb = 12 ∠120° A, I θc = 12 ∠30° A
    (C) I θb = 12 ∠30° A, I θc = 12 ∠120° A
    (D) I θb = 1290° A, I θc = 12 90° A

9. In a ∆-connected generator, there is a 120° difference between each line current and the nearest phase current.
    (A) True
    (B) False

10. In a Y-Y source/load configuration, the
    (A) Phase current, the line current, and the load current are all equal in each phase
    (B) Phase current, the line current, and the load current are 120° out of phase
    (C) Phase current and the line current are in phase, and both are 120° out of phase with the load current
    (D) Line current and the load current are in phase, and both are out of phase with the phase current

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Item Reviewed: MCQ on Three-Phase Systems in Power Applications - Set 01 Rating: 5 Reviewed By: Pranab Debnath
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