What is induction heating and how does it work?

Induction heating has been traditionally used to heat metal parts in applications such as soldering, brazing, hardening and melting of metals.  The power from modern induction heating systems is so controllable that it may be used to create ceramic components at temperatures in excess of 2400^oC or it may be used to gently cure adhesive for bonding the felt light trap to a 35mm film cassette.In brief, induction heating is a non-contact method of heating electrically conducting materials.  It involves a source of alternating current (the induction heater), induction coil (often called the work coil) and the part to be heated (the work piece).When an electrical current is made to alternate in a work coil, this produces an alternating magnetic field in and around the work coil.  If an electrically conducting part is placed within the magnetic field, a current is developed in that part (the work coil may be considered as the primary winding of a transformer and work piece as a short-circuit secondary winding).  The power that the current develops depends on several factors, these include:

a) The kilowatt rating of the induction heater.

b) The electrical resistivity of the work piece.

c) The configuration of the work coil and its relationship to the work piece.

In large pieces of metal, the intensity of the heating effect is local to the work coil and is greatest at the surface.  The effect reduces as the distance from the surface increases.  In order to heat small parts and to be able to use compact work coils, it is necessary to develop an alternating current of high frequency.  Sometimes when heating large components, it is desirable to use low or medium frequency so as to develop heating energy as deep as possible into the body of the part.  In the case of surface hardening, high frequency is used to develop heating energy literally in the skin of the component.