Induction heating is an ingenious and effective, non-contact process for electromagnetically heating electrically conductive materials such as metals and semiconductors. Heat is transferred to the material by a rapidly fluctuating magnetic field, created by running a high-frequency alternating current through an electromagnet specially designed for the application.
Induction heating is not only fast and efficient, but also provides a high-tech, precise heating technique.
Science of Induction Heating
An oscillating electrical current in an electromagnet gives rise to an oscillating electromagnetic field in the space around the magnet. The field carries energy and acts on charged particles, such as electrons, according to the Lorentz force law:
F = e(E + v × B).
When the oscillating electromagnetic field encounters a conductor, it forces electrons in the material back and forth rapidly. This is possible because the electrons in a conductor are free to move about the material. The motions of the electrons due to the electromagnetic field are known as induced currents in the conductor. These induced currents are where induction heating gets its name.
An electrical current in a conductor heats the material by resistive heating, which is the familiar I²R loss, such as that found when running a current through a wire. Resistive heating familiar I arises from the electrons hitting against the atoms in the conductor, increasing their temperature. By controlling the current in the electromagnet, we control the motion of the electrons and thus we control the heating of the material. In magnetic materials, the electromagnetic fields flip the magnetic domains back and forth rapidly, resulting in additional hysteresis heating. Heat is induced without ever touching the material: this technique forms the basis of the non-contact, electromagnetic heating that sets induction apart from other heating methods.
Induction heating can be used to heat non-conductive materials as well. Simply place the material in close contact with a conductor, which can then be effectively and efficiently heated by induction. The scope of applications where induction heating makes an impact is huge due to its versatility and high degree of customizability. With detailed electromagnet design, the electromagnetic field can be precisely shaped to determine what parts of the load to heat and how much to heat them.
These types of electromagnetic fields have no known effect on biological materials such as the human body. The non-conducting materials of the body do not allow electrons to move about freely, so there are no induced currents and no heating effects. The well-studied science behind induction technologies make them safe and reliable for operation.