Calculating power and Impedance

Discussion in 'Homework Help' started by regexp, Dec 21, 2010.

  1. regexp

    Thread Starter New Member

    Nov 20, 2010
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    Hi,

    One part of this question, i am uncertain of.

    "The current and Voltage through an impedance are known"
    u(t) = \sqrt2\cdot110cos(\omega t+85)V
    i(t) = \sqrt2\cdot0.4cos(\omega t+15)A

    Calculate the power and reactive power in the impedance.

    The powerangle is 70°
    So we have V_{rms} \cdot I_{rms} \cdot cos 70^\circ= 15A
    and V_{rms} \cdot I_{rms} \cdot sin 70^\circ = 41.34VA

    "Calculate the apparent power in the impedance"

    Apparent power = V_{rms} \cdot I_{rms} = 44

    "Calculate the impedance Z"

    Not sure about this one, is it simply 110/0.4 = 275Ω ?
     
    Last edited: Dec 21, 2010
  2. Georacer

    Moderator

    Nov 25, 2009
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  3. regexp

    Thread Starter New Member

    Nov 20, 2010
    24
    0
    Second try.

    Power P =  V_{rms} \cdot I_{rms} cos(\theta)

    Reactive power Q = V_{rms} \cdot I_{rms} sin(\theta)

    Apparent power S = IE(being the same as V_rms x I_rms)?
     
  4. Georacer

    Moderator

    Nov 25, 2009
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    That's what I would write too. But since power electronics is not my forte, I 'd like someone else to confirm it.
     
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