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  • Question

  • A three-phase △-connected generator is driving a balanced load such that each phase current is 12 A in magnitude. When I ?a = 12 ∠30° A, what are the polar expressions for the other phase currents?


  • Options
  • A. I ?b = 12 ∠150° A, I ?c = 12∠?90° A
  • B. I ?b = 12∠120° A, I ?c = 12∠30° A
  • C. I ?b = 12∠30° A, I ?c = 12∠120° A
  • D. I ?b = 12∠90° A, I ?c = 12∠90° A

  • Correct Answer
  • I ?b = 12 ∠150° A, I ?c = 12∠?90° A 

    • Three-Phase Systems in Power Applications problems

    Search Results

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

    • Options
    • A. 0 V
    • B. 90 V
    • C. 156 V
    • D. 180 V
      • Discuss
    • 2. For the circuit shown, determine ZTH for the portion of the circuit external to RL.


    • Options
    • A. 66.7 ∠?33.7° kΩ
    • B. 6.67∠?333.7° kΩ
    • C. 14.4 ∠?56.3° kΩ
    • D. 1.44 ∠?33.7° kΩ
      • Discuss
    • 3. In order to get maximum power transfer from a capacitive source, the load must

    • Options
    • A. have a capacitive reactance equal to circuit resistance
    • B. have an impedance that is the complex conjugate of the source impedance
    • C. be as capacitive as it is inductive
    • D. none of the above
      • Discuss
    • 4. Referring to the given circuit, find ZTH if R is 15 kΩ and RL is 38 kΩ.


    • Options
    • A. 89.82 ∠?51.3° kΩ
    • B. 19.2 ∠?38.3° kΩ
    • C. 9.38∠?51.3° kΩ
    • D. 180 ∠?38.3° kΩ
      • Discuss
    • 5. If two currents are in the same direction at any instant of time in a given branch of a circuit, the net current at that instant

    • Options
    • A. is zero
    • B. is the sum of the two currents
    • C. is the difference between the two currents
    • D. cannot be determined
      • Discuss
    • 6. In a △-connected generator, all of the phase voltages are

    • Options
    • A. zero
    • B. equal in magnitude
    • C. one-third of total
    • D. one-sixth of total
      • Discuss
    • 7. In a certain three-wire Y-connected generator, the phase voltages are 2 kV. The magnitudes of the line voltages are

    • Options
    • A. 2,000 V
    • B. 6,000 V
    • C. 666 V
    • D. 3,464 V
      • Discuss
    • 8. The most common type of ac motor is the

    • Options
    • A. single-phase induction motor
    • B. two-phase induction motor
    • C. three-phase induction motor
    • D. two-phase squirrel-cage motor
      • Discuss
    • 9. In a three-phase system, when the loads are perfectly balanced, the neutral current is

    • Options
    • A. zero
    • B. one-third of maximum
    • C. two-thirds of maximum
    • D. at maximum
      • Discuss
    • 10. In a △-connected source feeding a Y-connected load,

    • Options
    • 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
      • Discuss

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