Induction heating assemblies employ electromagnetic induction to generate heat. Specifically, induction heating assemblies include a conductor and an induction heating wire extending along (in close proximity to) the conductor. When an alternating electric current is passed through the conductor, an alternating magnetic field is established, which heats the induction heating wire by way of eddy currents and magnetic hysteresis.
Thus, induction heating assemblies are used in various applications that require heating, such as curing of composite structures (e.g., carbon-fiber-reinforced composites comprising thermoset resins) and heating of parts (e.g., preheating parts to be welded). For example, an induction heating assembly can be connected to (e.g., incorporated into or layered over) an insulating substrate (e.g., silicone rubber) to form an induction heating blanket. When the magnetic characteristics of the induction heating assembly at various temperatures are known, the alternating electric current supplied to the induction heating assembly may be controlled such that the associated induction heating blanket supplies the desired amount of heat.
Recently, induction heating assemblies have been manufactured in which the induction heating wire is spirally wrapped around the conductor (e.g., forms a helical coil around the conductor). Such a configuration advantageously positions the induction heating wire in particularly close proximity to the conductor.
However, unlike straight induction heating wires that can be precisely magnetically characterized using known equipment, such as an Epstein frame, magnetic characterization of spirally wrapped induction heating wires presents a challenge. The Epstein frame does not provide precise magnetic characterization of spirally wrapped induction heating wires. Furthermore, magnetic characterization of an induction heating wire prior to winding fails to account for the changes in magnetic properties that occur due to work hardening that is introduced by the winding process.
Accordingly, those skilled in the art continue with research and development efforts in the field of magnetic characterization.