Autoregulating, electrically shielded heater

Abstract

An autoregulating, electrically shielded heater employs a laminated structure having two magnetic alloy permeable materials of widely differing Curie point temperatures and preferably of differing resistivities. A constant current supply is connected across the laminate such that current flows in the laminae along parallel paths. Due to skin effect, the current is confined to a thin region of a first lamina which is located between the other lamina and the electrical return path. This first lamina has the lower Curie temperature and preferably the higher resistivity of the two laminae to produce heating proportional to I.sup.2 R.sub.1. When the Curie temperature of the first lamina is approached, the current spreads into the other lamina which may have a lower resistivity and higher Curie temperature and heating is obtained by I.sup.2 R.sub.2 where I.sup.2 is a constant due to the constant current source and preferably R.sub.2 <R.sub.1. Thus, power is reduced and temperature is maintained at or about the Curie temperature of the first layer. The high permeability of the second lamina prohibits the current from penetrating deeply into the second laminae whereby a low frequency power supply may be used without radiation of the electro-magnetic field.

Dependencies are inferred from the claim text.