04256945 is referenced by 393 patents and cites 8 patents.

The heating element consists of a substrate or core of a non-magnetic material having high thermal and electrical conductivity, clad with a surface layer of a ferromagnetic material of relatively low electrical conductivity. When the heating element is energized by a source of high frequency alternating current, the skin effect initially confines current flow principally to the surface layer of ferromagnetic material. As temperature rises into the region of the Curie temperature of the ferromagnetic material, however, the decline in magnetic permeability of the ferromagnetic material causes a significant lessening of the skin effect, permitting migration of current into the high conductivity non-magnetic core, thereby simultaneously enlarging the cross-sectional area of the current flow path and expanding it into the highly conductive material; the resistance of the heating element becomes less due to both causes. By selecting the proper frequency for energization, by regulating the source to produce constant current, and by selecting dimensions and material parameters for the heating element, temperature regulation in a narrow range around the Curie temperature of the ferromagnetic material can be produced, despite considerable fluctuations in thermal load.

Title
Alternating current electrically resistive heating element having intrinsic temperature control
Application Number
6/71682
Publication Number
4256945
Application Date
August 31, 1979
Publication Date
March 17, 1981
Inventor
John F Krumme
Woodside
CA, US
Philip S Carter
Palo Alto
CA, US
Agent
C Michael Zimmerman
Assignee
Iris Associates
CA, US
IPC
H05B 5/00
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