THREE PHASES MULTIPLE CHOICE QUESTIONS

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 0° 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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