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Danfoss autopsy

Discussion in 'Electronic Basics' started by J.E.B., Mar 31, 2007.

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  1. J.E.B.

    J.E.B. Guest

    Recently I dissected a danfoss variable speed a.c. moter drive. I
    found what looked like two transformers with only to wires coming from
    each. Are these transformers? If so how would this work? anybody
    familar with danfoss drives?
     
  2. They sound like inductors. I'll bet that the cores consist
    of a stack of Es and a stack of Is separated by a thin
    spacer, rather than interleaved Es and Is the way
    transformers are made.
     
  3. J.E.B.

    J.E.B. Guest

    Thanks for the reply John. Pardon my ignorance, But what purpose would
    these serve? P.S. This is a VLT 5000 series BTW.
     
  4. I can only guess, but inductance limits the rate of rise of
    current when a voltage is switched on. This effect can be
    used as a way to figure out that the motor leads are shorted
    and switch back off before the short produces damaging
    current levels, or as high frequency noise filter
    components. If being used in the motor circuit, I would
    have expected 3 of them. With only two, they are more
    likely part of the supply noise filter. Is this drive
    powered by single phase or 3 phase?
     
  5. J.E.B.

    J.E.B. Guest

    3 phase. 460 delta.
     
  6. Either they are chokes or there is also one large wire going through each.
     
  7. J.E.B.

    J.E.B. Guest

    These are wound with what appears to be 16 to 14 gauge.
     
  8. J.E.B.

    J.E.B. Guest

  9. Can you trace if these two inductors are part of the DC
    filter between the 3 phase rectifier and the storage capacitors?
     
  10. Pretty much chokes then.
     
  11. 4. Intermediate circuit coils

    Smooths the intermediate circuit current and limits the load on AC line and
    components (AC line transformer, wires, fuses and contactors).
     
  12. jntel

    jntel Guest

    They are DC line reactors. There is one placed in the (-) and one placed in
    the (+) leg between the 3 phase input full wave bridge rectifier and the
    capacitor bank. They are used for harmonic control. External input line
    reactors are not needed.

    Jeff
     
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