A transformerâs leakage impedance is a series element that reï¬ects imperfections in. the windings. The real component of the leakage impedance is the resistance of the. windings. Its reactive component is due to leakage ï¬ux,i.e. ï¬ux in the magnetic circuit. that does not contribute to coupling the windings. Figure1depicts a transformerâs equivalent circuit with impedances referred to the sec-. ondary.