Polyphase System MCQ’s

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This set of Network Theory Multiple Choice Questions & Answers (MCQs) focuses on “Polyphase System”.

1. The percentage of power increased from single phase to three phase is?
a) 50
b) 100
c) 150
d) 200

2. When the power factor is __________ the power becomes zero 100 times a second in a 50Hz supply.
a) 0
b) 1
c) 2
d) 3

3. The power generated by a machine increases _____________ percent from single phase to two phase.
a) 40.4
b) 41.4
c) 42.4
d) 43.4

4. Which motors are called self-starting motors?
a) single phase
b) two phase
c) three phase
d) four phase

5. In a two phase generator, the armature has two distinct windings that are displaced __________ apart.
a) 45⁰
b) 90⁰
c) 135⁰
d) 180⁰

6. Phase sequence depends on the _________________
a) field
b) rotation of the field
c) armature
d) rotation of the armature

7. In three phase system, the three voltages (currents) differ in phase by __________electrical degrees from each other in a particular sequence.
a) 30
b) 60
c) 90
d) 120

8. In three phase system at any given instant, the algebraic sum of three voltages must be?
a) 0
b) 1
c) 2
d) 3

9. If RR, YY and BB constitutes three phase sequence if VRR = Vmsinωt its corresponding field magnets are in clockwise direction, then VYY =?
a) Vmsinωt
b) Vmsin(ωt+120⁰)
c) Vmsin(ωt-120⁰)
d) Vmsin(ωt-240⁰)

10. If RR, YY and BB constitutes three phase sequence if VRR = Vmsinωt its corresponding field magnets are in clockwise direction, then the value of VBB is?
a) Vmsin(ωt-240⁰)
b) Vmsin(ωt-120⁰)
c) Vmsin(ωt+240⁰)
d) Vmsinωt

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