In inductive heating applications, the machine part that generates the magnetic field is called the inductor or coil.
The inductor is the tool that performs the actual heating and must therefore be adapted to the component's geometry and the required heating area to keep the air gap as small as possible. Compared to other heating methods, inductive heating is characterised by a high power density and a fast heating time. This is achieved by using hollow copper sections for the inductor, so that it can be operated with very high currents and the resulting heat losses can be dissipated via cooling water that flows through the hollow sections.
In the simplest case, the inductor is a conductor loop around the workpiece and is connected to an alternating current source. Since, in a first approximation, the current induced in the workpiece flows directly below the inductor loop across the workpiece surface, the heating can be influenced locally by the choice of the loop form; complex heating tasks can be achieved by more complicated inductor shapes. If the design of the heating loop alone is insufficient for the desired heating, additional elements for concentrating the magnetic field (e.g. magnetic steel sheets or soft magnetic cores) are used. The complex interaction of the electromagnetic field and temperature field with the workpiece geometry requires special experience in dimensioning inductors and is nowadays supported by numerical calculations.
When power is transferred to the workpiece, the magnetic field and current act jointly on the same point. Consequently, resulting forces also occur on both the workpiece and inductor (repelling in the case of pure copper coils), while alternating forces occur at double the excitation frequency. The resulting forces need to be absorbed and the system must be designed accordingly. The alternating forces can cause vibrations and noise emissions.