A source of high frequency electricity (high frequency power
supply) is used to drive a large alternating current through an induction
coil. In induction heating this is known
as the “work coil”.
The passage of current through this induction heating coil
generates a very intense and rapidly changing magnetic field in the space in
the work coil. The work piece to be
heated is placed in this intense alternating magnetic field.
The alternating magnetic field induces a current flow in the
conductive work piece. The arrangement
of the work coil and the work piece can be thought of as an electrical
transformer. The work coil is like the
primary where electrical energy is fed in, and the work piece is like a single
turn secondary that is short-circuited.
This causes tremendous currents to flow through the work piece. These are known as “eddy currents” which
generates high levels of I²R
losses in work piece causing temperature to rise. In addition to this, the high frequency used
in induction heating also has a phenomenon known as “skin effect". This skin effect forces the alternating
current to flow in a thin layer towards the surface of the work piece. The skin effect increases the effective
resistance of the metal to the passage of high level of current. Therefore it greatly increases the heating
effect of the induction heater caused by the current induced in the work piece.
