A model of losses in twisted-multistranded wires for planar windings used in domestic induction heating appliances

In this paper, a model of the losses in twisted-multistranded wires for planar windings, is developed and experimentally validated. This model is applied to estimate the losses in the inductors used in domestic induction heating appliances. Multistranded wires are employed in some special heating applications requiring currents at frequencies up to 100 kHz, in order to avoid a high losses penalization. These wires are manufactured by bunching up to thousands of fine strands. The model of losses is based on the superposition of the different loss effects in the wire (DC, skin, and proximity). Moreover, the developed model is based on the existing analogy between the round wires and the multistranded ones. This analogy permits to develop a fully analytical model of the losses including the dependence of the frequency, properties of the vessel, and geometrical and constructive parameters of the wire. The model is experimentally validated by means of several inductors built with different wires and measured under both loaded and not-loaded conditions.