Gradient induction heating of a workpiece using multiple coils and variable frequency power supplies

摘要

An apparatus and process for gradient induction heating or melting of a workpiece with a plurality of induction coils, each induction coil being connected to a power supply that may have a tuning capacitor connected across the input of an inverter. The coils are sequentially disposed around the workpiece. The inverter has a pulse width modulated AC power output that may be in synchronous control with the pulse width modulated AC power outputs of the other power supplies via a control line between the controllers of all power supplies.