THREE PHASES MULTIPLE CHOICE QUESTIONS

00:30:00 to be answered :15
Question 1

In a Y-connected circuit, between each line voltage and the nearest phase voltage, there is a phase angle of

 


A 90°
B
C 60°
D 30°

Question 2

Polyphase generators produce simultaneous multiple sinusoidal voltages that are separated by


A certain constant frequencies
B certain constant voltages
C certain constant voltages
D certain constant frequencies

Question 3

A constant load power means a uniform conversion of


A electrical to mechanical energy
B voltage to current
C mechanical to electrical energy
D current to voltage

Question 4

If in a Y-connected ac generator, each phase voltage has a magnitude of 90 VRMS, what is the magnitude of each line voltage?


A 0 V
B 90 V
C 156 V
D 180 V

Question 5

In a Y-connected circuit, the magnitude of each line current is


A one-third the phase current
B three times the corresponding phase current
C equal to the corresponding phase current
D zero

Question 6

The most common type of ac motor is the


A single-phase induction motor
B two-phase induction motor
C three-phase induction motor
D two-phase squirrel-cage motor

Question 7

In a Y-Y source/load configuration, the


A phase current, the line current, and the load current are 120° out of phase
B line current and the load current are in phase, and both are out of phase with the phase current
C phase current, the line current, and the load current are all equal in each phase
D phase current and the line current are in phase, and both are 120° out of phase with the load current

Question 8

In a three-phase system, the voltages are separated by


A 120°
B 90°
C 45°
D 180°

Question 9

In a three-phase system, when the loads are perfectly balanced, the neutral current is


A one-third of maximum
B at maximum
C zero
D two-thirds of maximum

Question 10

In a certain three-wire Y-connected generator, the phase voltages are 2 kV. The magnitudes of the line voltages are


A 6,000 V
B 666 V
C 2000 V
D 3464 V

Question 11

In a certain Y-Y system, the source phase currents each have a magnitude of 9 A. The magnitude of each load current for a balanced load condition is


A 3 A
B 9 A
C 27 A
D 12 A

Question 12

In a two phases generator, electrical displacement among two phases or windings is ….. electrical degrees.


A 120°
B 90°
C 180°
D None of the above

Question 13

The benefit of star-connected supply system is that...


A Line current is equal to phases current
B Two voltage can be used
C Phase sequence can be easily changed
D It is a simple arrangement

Question 14

If a balanced delta load has an impedance of 6+j9 ohm per phase, then, impedence of every phase of equivalent star load is…

 

 


A 6+j9 ?
B 2+j3 ?
C 12+j18 ?
D 3+j45 ?

Question 15

The algebraic sum of instantaneous phase voltage in a a three-phase circuit is equivalent to


A Zero
B Line voltage
C Phase voltage
D None of the above



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