FLUX DENSITY IN TRANSFORMER CORE

Discussion in 'General Electronics Chat' started by ujjwal agarwal, Apr 23, 2015.

  1. ujjwal agarwal

    Thread Starter New Member

    Apr 23, 2015
    6
    0
    can any tell me why do we need minimum flux density in a transformer core??
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,014
    3,233
    I wasn't aware the you did.
    Where did you read that?
     
  3. ujjwal agarwal

    Thread Starter New Member

    Apr 23, 2015
    6
    0
    on net... i too wasnt aware of this..
    but i think it must be to avoid core saturation.
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,014
    3,233
    Certainly you need to avoid core saturation but I don't see how that's related to a minimum flux density. :confused:
     
  5. Ramussons

    Active Member

    May 3, 2013
    557
    92
    Maybe he means Minimum Flux (Density) Leakage to be ensured in transformer design for good regulation .....
     
  6. uwed

    Member

    Mar 16, 2015
    64
    17
    Generally, the product of winding window and core cross section tells you about the transformer size. It is a transformer with an iron core transferring the power defined by U1 and I1 at a given frequency f. You are free to make the flux density B very small, but the transformer will grow in size, cost and winding losses.
    upload_2015-4-24_13-35-18.png
     
    ujjwal agarwal likes this.
  7. MrAl

    Well-Known Member

    Jun 17, 2014
    2,433
    490
    Hi,

    When you post a formula like that you should show what every variable stands for, and what dimensions it is in such as inches, meters, etc., Hertz, etc.
     
  8. uwed

    Member

    Mar 16, 2015
    64
    17
    Sorry, you are right:

    Af, Aw ... core cross section [m2], windings window area [m2]
    kw .... windings filling factor --> describes insulation , no dimension, typical values often 0.4..0.7
    Srms ... current density in wire [A/m2] (natural convection 1e6...3e6A/m2, forced convection cooling 3e6...5e6A/m2, oil transformer 5e6...7e6A/m2)
    B ... peak flux density [T]; has to be below saturation (iron core B<1.7T, nanocristalline B<1T, ferrite B<0.35T, amorpeous core B<1.4T)
    U1 ... rms of primary voltage [V]
    I1 ... rms of primary current [A]
    f ... operating frequency [Hz]

    Actually, I put the equation to show that the transformer size is inverse proportional to the flux density.
     
    Last edited: Apr 24, 2015
Loading...