Induction Heating Using Induction Coils in Series-Parallel Circuits

• US 20130082047A1
• Filed: 09/29/2011
• Published: 04/04/2013
• Est. Priority Date: 09/29/2011
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Matsen, Marc Rollo, Geren, William Preston, Miller, Robert James, Negley, Mark Alan, Dykstra, William Chet
• Granted Patent: US 9,820,339 B2
• Time in Patent Office: Days
• US Class Current: 219/634
• CPC Class Codes: B29C 2035/0811 using induction
• CPC Class Codes: B29C 35/0805 using electromagnetic radiation
• CPC Class Codes: H05B 2206/023 using the curie point of the material in which heating current is being generated to control the heating temperature
• CPC Class Codes: H05B 6/06 Control, e.g. of temperature, of power
• CPC Class Codes: H05B 6/105 using a susceptor

Abstract

A part is inductively heated by multiple, self-regulating induction coil circuits having susceptors, coupled together in parallel and in series with an AC power supply. Each of the circuits includes a tuning capacitor that tunes the circuit to resonate at the frequency of AC power supply.

Claims

1. An induction heating method, comprising:

selecting at least two induction coil circuits each including a susceptor having a Curie temperature;

coupling the induction coil circuits in parallel with each other and in series with an AC power supply; and

shunting power away from one of the induction coil circuits to the other induction coil circuits when the susceptor of the one circuit substantially reaches its Curie temperature.

2. The method of claim 1, further comprising:

rebalancing the power applied by the AC power supply to the other induction coil circuits when power is shunted away from the circuit that has reached its Curie temperature.

3. The method of claim 2, wherein the rebalancing of the power is includes maintaining the power delivered to the other induction coil circuits substantially constant.

4. The method of claim 1, wherein shunting the power away from the induction coil circuit that has reached its Curie temperature includes detuning the circuit.

5. The method of claim 4, further comprising:

tuning the resonant frequency of each of the induction coil circuits to match the frequency of the AC power supply.

6. The method of claim 4, further comprising:

tuning each of the induction coil circuits to substantially match the input resistance of the AC power supply and cancel the inductive reactance of the circuit.

7. The method of claim 6, wherein the tuning includes using a transformer to scale the resistance of one of the induction coil circuits that has reached its Curie point to substantially match the resistance of the AC power supply.

8. A method of heating a part, comprising:

providing multiple induction coil heating circuits, each of the circuits including an induction heating coil and a susceptor wherein the susceptor is magnetically coupled with the coil and has a preselected Curie point;

electrically coupling the circuits in parallel with each other;

placing the induction heating coils in proximity with the part;

coupling an AC power supply in series with the parallel coupled circuits;

using the AC power supply an alternating current the circuits; and

tuning the resonant frequency of each of the circuits to substantially cancel the inductive reactance of the circuit.

9. The method of claim 8, wherein the tuning is performed using a capacitor having a value that substantially cancels the inductive reactance of the circuit.

10. The method of claim 8, wherein the tuning is performed using a transformer to scale the resistance of each of the circuits to match the AC power supply.

11. The method of claim 8, further comprising:

rebalancing the power applied by the AC power supply to the circuits devices when the susceptor in at least one of the circuits reaches its Curie temperature.

12. The method of claim 11, wherein the rebalancing of the power is performed by maintaining the power delivered to the other heating devices substantially constant.

13. An induction heating device, comprising:

an AC power supply; and

a group of induction coil circuits each including an induction heating coil and a susceptor having a preselected Curie temperature;

wherein the induction coil circuits are coupled in parallel with each other and in series with the AC power supply.

14. The induction heating device of claim 13, wherein each of the induction coil circuits is tuned to match the input resistance of the AC power supply.

15. The induction heating device of claim 13, wherein each of the induction coil circuits is tuned to resonate at the frequency of current supplied by the AC power supply.

16. The induction heating device of claim 13, wherein each of the induction coil circuit includes a capacitor providing the circuit with a value of capacitance reactance that is substantially equal to the inductive reactance of the circuit when the susceptor is below its Curie temperature.

17. The induction heating device of claim 16, wherein the capacitor is a discrete capacitor.

18. The induction heating device of claim 16, wherein the capacitor is formed by capacitance that is distributed within the circuit.

19. The induction heating device of claim 13, further comprising:

a controller for controlling the power supply to redistribute power supplied to the induction coil circuits when one or more of the susceptors reaches its Curie temperature.

20. The induction heating device of claim 13, further comprising:

a thermally conductive matrix in which the induction coils and the susceptors are embedded.