Does Magnetics Designer use an algorithm to correct for fringing in long air gaps?
It is convenient to set the magnetizing inductance of a transformer by inserting an air gap. When this is done, flux is no longer confined to the core. Flux between the core halves will begin to fringe as the gap is increased so that the effective gap area will be larger than the physical cross section. The fringing flux creates several problems: • For laminated cores, some flux passes normal to the lamination resulting in increased eddy current losses. • Flux will intercept windings transversely, causing eddy current losses in the winding. • As gap length increases, fringing increases its effective area. Magnetics Designer accounts for gap fringing when calculating the effective gap area used in permeability computations. The resulting area multiplier is also made available to the user in the Kgap function. This function calculates the ratio of effective area to core area according the following: Kgap(lg) = (1 + lg / sqrt(Ac)*log (2*(lwindow)/(lg+1e-6))) ; where lg = gap length in cm
