Calculation of self and mutual impedances between sections of transformer windings

The author shows how a new frequency-dependent impedance formula, derived on the assumption of a solid homogeneous core, may be adapted to permit calculation of the self and mutual impedances of coil sections on a practical transformer core. Experimental measurements, in comparison with calculated values, show that the effects of the laminations can be accurately simulated by using two distinct resistivities in different parts of the basic formula. A method is given for determining these quantities experimentally. Application of the resulting formula in transient analysis automatically accounts for the effects of transient flux penetration into the transformer core, including the effects of frequency-dependent inductances and transient eddy currents in the core laminations