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Harmonic Filter Resonant Frequency Calculation

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  1. ElectricalTestTech's Avatar
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    Harmonic Filter Resonant Frequency Calculation

    Which order harmonic would be effectively removed from a power system by applying a single-tuned filter with a 0.55 μF capacitor and a 500 mH inductor?

    How do you calculate this?

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    Quote Originally Posted by ElectricalTestTech View Post
    Which order harmonic would be effectively removed from a power system by applying a single-tuned filter with a 0.55 μF capacitor and a 500 mH inductor?

    How do you calculate this?
    I believe the formula is 1/(2PI*SQRT(LC))

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    Quote Originally Posted by Wanderer20001us View Post
    I believe the formula is 1/(2PI*SQRT(LC))
    Can you walk us through this calculation? I have tried doing it several times and haven't come up with what they say is the correct answer yet.

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    Quote Originally Posted by kchenoweth View Post
    Can you walk us through this calculation? I have tried doing it several times and haven't come up with what they say is the correct answer yet.
    L*C =0.5*0.00000055=0.000000275
    sqrt(0.000000275)=0.0005244
    2pi*0.0005244=0.003294
    1/0.003294=303.49hz
    303.5hz/60hz=5.058 or 5th Harmonic

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    I've seen a slightly different version of this question:

    A harmonic filter bank consists of a capacitor bank at 8uF and 40mH. Which harmonic is this bank eliminating?

    f = 1 / (2 * pi * sqrt(L * C))
    f = 1 / (2 * pi * sqrt(0.040 * 0.000008))
    f = 1 / (2 * pi * sqrt(0.00000032))
    f = 1 / (2 * pi * 0.00056568542)
    f = 1 / (0.00355430631942971339162580115316)
    f = 281.35

    Harmonic @ 60 Hz = 281.35 / 60 = 4.689 = 5th harmonic

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