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LCM inductor and Air core inductor difference

Discussion in 'General Electronics Discussion' started by strameshkumar, Feb 21, 2014.

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  1. strameshkumar


    Feb 23, 2012
    Hi ,
    I want test the DC-DC converter(VYC30W-Q24-D15) at my Lab.I have two queries.
    1.) I have seen the data sheet mentioned LCM inductor. But i have only air core inductor. if i use this aire core inductor instead of LCM inductor, How it will affect my circuits.
    2) If i use polarised capacitor in place of non-polarised capacitor, how it will affect my output voltage?

    Thanks in Advance
    Ramesh T

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    1) the inductor in the schematic is a common mode suppressor choke. It is wound such that the magnetic fields from the operating currents in both coils cancel (they have the same amplitude but opposite direction). Therefore the inductor "sees" no net magnetic flux. If a common mode noise is present, the magnetic fileds do not cancel, they add up. Therefore the inductance of the choke is high for common mode noise.
    It is next to impossible to create such an inductor without a magnetic core while still obtaining a useful inductance.

    2) in fact, C0 is polarized.
    It is not the polarization that counts here, since you're dealing with DC. It is the different construction of the capacitors. C0 presumably is a large electrolytic capacitor. This kind oc capacitor can store a lot of energy, but has a comparatively high impedance at high frequencies. It will not suppress high frequency noise.
    The unpolarized capacitors in the schematic are likely to be ceramic or foil capacitors. While these cannot store a lot of energy, they behave well at high frequencies and filter noise.
    You see, there is a reason why different types of capacitors are used.
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