Single turn work coil and integrated matching transformer for medium and high frequency induction heating

A single turn work coil with an integrated matching transformer for medium and high frequency induction heating application is proposed. The secondary of the transformer is an extension of the work coil, and the primary is situated within the hollow, water cooled secondary. Advantages of the construction include: low series (leakage) inductance of the coaxial transformer; and liquid cooling of work coil, coaxial transformer and switching devices. Higher efficiency of the work coil is achieved by low leakage inductance, which gives better coupling between the converter and the workpiece. Simulation results compare the multi and single turn coils with respect to work coil efficiency and investigate the difference in current distributions. Experimental results are presented, using a series resonant power converter with a hybrid analogue and digital controller