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Instantaneous Voltage

  1. Feb 17, 2014 #1
    A 50 Hz ac three phase supply has a peak voltage of 100 V. Calculate the instantaneous voltage of each phase at a time of 7.5 ms.

    Looked all over google and cant seem to find an equation for this?

    Can anyone point me in the right direction?
  2. jcsd
  3. Feb 17, 2014 #2


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    Staff: Mentor

    Can you attach a pic of the illustration that accompanied this question?
  4. Feb 17, 2014 #3


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    Gold Member

    Think about what an AC waveform is. Its a sine wave. the standard form for a sine wave is

    V=A*cos(wt+theta) where A=amplitude, w=frequency in radians, & theta=delay.

    note with a 3phase system the voltages are evenly out of phase with one another, so they are evenly spread across the unit circle (360 degrees)

    Using this information give it another try
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