LTSpice, Current transducer - secondary current offset

Discussion in 'The Projects Forum' started by jaworski_m, Mar 13, 2013.

  1. jaworski_m

    Thread Starter New Member

    Mar 13, 2013
    2
    0
    Hello,
    I've built an inverter with current measurement using current transducers (CT) in each leg.

    Simulation works fine except CT part.
    There is a problem with the current on the secondary side (L6,L8) of the CTs. Current in L6, L8 is not zero (ca.0.5A offset) when current on primary side (L5, L7) is zero.

    I tried changing orientation of secondary side coils (windings beginnings) but didn't help.

    Can you tell me why there is an offset on the secondary side of CT?

    Thank you.
     
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    656
    Is Ucomp a negative voltage when the secondary currents are flowing?
    Part of your schematic is obviously missing. Can you post the .asc file for the entire circuit, so we can simulate it?
     
    Last edited: Mar 13, 2013
  3. ifixit

    Distinguished Member

    Nov 20, 2008
    638
    108
    1. Are you saying it is a DC current?
    2. Is there a voltage across L6 & L8 as well?
    3. Could there be a -ve voltage feeding back via Ucomp?
    Regards,
    Ifixit
     
  4. jaworski_m

    Thread Starter New Member

    Mar 13, 2013
    2
    0
    Hello,
    Thank you for your answer.
    Simulation in the attachment.

    Steady state @ ca.8ms
    Inverter leg current (primary) - L5, L7
    Inverter leg current (secondary) - L6, L8
    Primary trafo total current - L3
    Primary trafo voltage - U1-U2
     
  5. ifixit

    Distinguished Member

    Nov 20, 2008
    638
    108
    R7 & R10 should be the terminating resistance (4r8) so that both polarities of the signal are terminated equally. Change R5 to 10K to to provide the proper smoothing of the DC output, Ucomp.

    Regards,
    Ifixit
     
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