Integrated water cooled transformer and work coil for middle frequency induction heating applications

An integrated water-cooled transformer and single-turn work coil for middle-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. An advantage of the construction is liquid cooling of work coil, coaxial transformer, and switching devices. The coaxial construction of the transformer achieves low leakage inductance, which gives better coupling between the converter and the workpiece. Simulations were conducted to compare the multi-turn and single-turn coils with respect to work coil efficiency, and the difference in current distributions is investigated. It is shown that a single-turn work coil can be more effective than the normal multi-turn work coil and the coaxial transformer has less leakage inductance than other transformers. Different cross-sectional shapes of the single-turn coil and different winding geometries of the transformer are investigated by means of simulation. A prototype integrated transformer and work coil was constructed, and experimental results are presented