Induction heating is the process of heating an electrically conducting object (usually a metal) by electromagnetic induction, where eddy currents (also called Foucault currents) are generated within the metal and resistance leads to Joule heating of the metal. An induction heater includes an electromagnet through which a high-frequency alternating current (AC) is passed (i.e., an inductive coil coupled to a susceptor), to generate eddy currents in the metal (i.e., the susceptor). The frequency of AC used in induction heating depends on the object size, material type, coupling (between the work coil and the object to be heated) and the penetration depth. Heat may also be generated by magnetic hysteresis losses in materials that have significant relative permeability.
An exemplary prior art susceptor is shown in FIG. 1. As shown in FIG. 1, the prior art susceptors 100 are made of a single piece of material. Induction heating has limitations as to temperature uniformity due to induction coil pattern being superimposed in the susceptor and because the nature of induction heating is to heat edge to center. The heating at the edges first is an effect of larger eddy currents being at the side boundaries first and then radiating inward. In general, the temperature at the center is at least more than 20° C. lower than the edge.
Prior art attempts to address non-uniform heating in inductive heating systems have focused on changes to coil densities, coil shape, position of coil to susceptor. These coil design changes are very time consuming, expensive and space constraining.
Another problem with prior art susceptors is that the susceptor material is fragile and the susceptor is costly. If the susceptor is heated too quickly or the surface is damaged in any way, the susceptor material cracks and breaks. Whenever any part of the susceptor is cracked or warped, the whole susceptor is destroyed and must be replaced.
Accordingly, new developments and improvements are needed.
USPTO Backgrounds
USPTO Backgrounds