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Home Electrical Engineering Three-Phase Systems in Power Applications Comments

  • Question
  • 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

  • Correct Answer
  • zero 


  • Three-Phase Systems in Power Applications problems


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    • 1. 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
    • 2. 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
    • 3. 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
    • 4. 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
    • Discuss
    • 5. 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
    • 6. 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
    • 7. In a balanced three-phase load, each phase has

    • Options
    • A. an equal amount of power
    • B. one-third of total power
    • C. two-thirds of total power
    • D. a power consumption equal to IL
    • Discuss
    • 8. In a Y-connected circuit, the magnitude of each line current is

    • Options
    • A. one-third the phase current
    • B. three times the corresponding phase current
    • C. equal to the corresponding phase current
    • D. zero
    • Discuss
    • 9. Polyphase generators produce simultaneous multiple sinusoidal voltages that are separated by

    • Options
    • A. certain constant phase angles
    • B. certain constant frequencies
    • C. certain constant voltages
    • D. certain constant currents
    • Discuss
    • 10. In a △-connected source driving a △-connected load, the

    • Options
    • A. load voltage and line voltage are one-third the source voltage for a given phase
    • B. load voltage and line voltage are two-thirds the source voltage for a given phase
    • C. load voltage and line voltage cancel for a given phase
    • D. load voltage, line voltage, and source phase voltage are all equal for a given phase
    • Discuss


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