The paper presents five structured design methodologies for third-order LCC voltageoutput resonant converters. The underlying principle of each technique is based on an adaptation of a FMA equivalent circuit that accommodates the nonlinear behaviour of the converter. In contrast to previously published methods, the proposed methodologies explicitly incorporate the effects of the transformer magnetising inductance. Furthermore, a number of the methodologies allow the resonant-tank components to be specified at the design phase, thereby facilitating the use of standard off-the-shelf components. A procedure for sizing the filter capacitor is derived, and the use of error mapping, to identify parameter boundaries and provide the designer with a qualitative feel for the accuracy of a proposed converter design, is explored.