Control system for a microwave oven, a microwave oven using such a control system and methods of making the same

• US 5,653,906 A
• Filed: 10/31/1994
• Issued: 08/05/1997
• Est. Priority Date: 09/07/1994
• Status: Expired due to Fees

• Current Assignee: Robertshaw Controls Company (Schneider Electric SE)
• Original Assignee: Robertshaw Controls Company (Schneider Electric SE)
• Inventors: Pattok, Greg R., Fowler, Daniel L., Tanis, Bruce E.
• Primary Examiner(s): Leung, Philip H.
• Application Number:
  US08/332,112
• Time in Patent Office: 1,009 Days
• Field of Search: 219/716, 219/717, 219/760, 219/702, 219/710, 323/299, 323/301, 323/258, 323/255
• US Class Current: 219/716
• CPC Class Codes: H05B 6/6461 using fire or fume sensors
• CPC Class Codes: H05B 6/666 Safety circuits emergency protective circuits in general H02H

Abstract

A control system for a microwave oven having a magnetron unit, a microwave oven using such a control system and methods of making the same are provided, the system being adapted to interconnect a power source to a transformer unit of the magnetron unit to operate the same, the system comprising a unit for determining the actual voltage level of said power source to be utilized at that time and being adapted to interconnect the power source to a particular tap of the transformer unit if the determined power level is above a certain value and to interconnect the power source to another tap of the transformer unit if the determined power level is below the certain value.

Claims

1. A control system for a microwave oven having a magnetron including a transformer, said control system further comprising an electrical circuit to interconnect an electrical power source through a conductor to said transformer to operate said magnetron, further including an actual amperage detector of the electrical current flowing from said power source through said conductor to said transformer at that time so as to monitor the operating condition of said magnetron;

and wherein

said actual amperage detector comprises;

a current sampling circuit and means for determining from said current sampling circuit the highest reading on said current having a sinusoidal wave form.

2. A control system as set forth in claim 1 wherein said actual amperage detector comprises a transformer coil having part of said conductor passing therethrough, whereby said transformer coil comprises a secondary coil of a transformer and said part of said conductor comprises a primary of said transformer.

3. A control system as set forth in claim 2 wherein said actual amperage detector comprises a microprocessor having an A to D converter, said electrical circuit comprising a differential amplifier having an input operatively interconnected to said secondary coil and an output operatively interconnected to said A to D converter.

4. A control system as set forth in claim 1 wherein said operating condition that is being monitored comprises the condition of said magnetron becoming conductive.

5. A control system as set forth in claim 1 wherein said magnetron comprises a plurality of magnetrons and wherein said operating condition that is being monitored is the amount of current being drawn when at least one of said magnetrons is being turned on to determine if the particular turned on magnetron is operating at a certain amperage rating thereof.

6. A microwave oven having a magnetron including a transformer, said microwave oven having a control system comprising an electrical circuit having a conductor, to interconnect an electrical power source through said conductor to said transformer to operate said magnetron, wherein said control system comprises an actual amperage detector of electrical current flowing from said power source through said conductor to said transformer at that time so as to monitor the operating condition of said magnetron means;

and wherein

said actual amperage detector comprises;

a current sampling circuit and means for determining from said current sampling circuit the highest reading on said current having a sinusoidal wave form.

7. A microwave oven as set forth in claim 6 wherein said actual amperage detector comprises a transformer coil having part of said conductor passing therethrough, whereby said transformer coil comprises a secondary coil of a transformer and said part of said conductor comprises a primary of said transformer.

8. A microwave oven as set forth in claim 7 wherein said actual amperage detector comprises a microprocessor having an A to D converter, said electrical circuit comprising a differential amplifier having an input operatively interconnected to said coil secondary and an output operatively interconnected to said A to D converter.

9. A microwave oven as set forth in claim 6 wherein said operating condition that is being monitored comprises the condition of said magnetron becoming conductive.

10. A microwave oven as set forth in claim 6 wherein said magnetron comprises a plurality of magnetrons and wherein said operating condition that is being monitored is the amount of current being drawn when at least one of said magnetrons is being turned on to determine if the particular turned on magnetron is operating at a certain amperage rating thereof.

11. A control system for a microwave oven having a magnetron, said control system comprising:

a current transforming device responding to an input current variably drawn by said magnetron from an external power source, said current transformer producing an output current proportional to said input current;

a scaling device responding to said output of said current transformer, said scaling device producing a scaled, amplified and rectified output proportional to said input current; and

a computing device responding to said scaling device, wherein said computing device determines the actual amperage of said input current so as to monitor the operating condition of said magnetron; and

wherein

said computing device comprises an analog to digital converter connected to said scaling device output; and

said computing device determines the actual amperage of said input current by taking several samples of digital signals which corresponds to said input current thereby finding the highest reading of a sinusoidal wave form to determine the peak current.

12. The control system of claim 11, wherein said scaling device comprises a differential amplifier.

13. The control system of claim 11, wherein said output from said scaling device is scaled to be a maximum of 5 volts DC when said input current is greater than 30 amps.

14. The control system of claim 11, wherein said microwave oven has several magnetrons and said computing device monitors the operating condition of said several magnetrons.

15. A method of controlling a microwave oven having a magnetron, comprising the steps of:

transforming magnetic flux from an input current variably drawn by said magnetron from an external power source to a corresponding signal, wherein said corresponding signal is proportional to said input signal;

determining the amperage of said input current from said corresponding signal; and

monitoring the condition of said magnetron from the determined amperage of said input current; and

wherein

said step of determining the amperage comprises;

sampling said corresponding signal; and

determining the highest reading on said input signal having a

sinusoidal wave form from said sampling of said corresponding signal.

16. The method as set forth in claim 15, further comprising the step of converting said corresponding signal from an analog signal to a digital signal.

17. The method as set forth in claim 15, wherein said transforming step comprises:

transforming the magnetic flux from said input current to a small AC signal;

rectifying said small AC signal; and

scaling said small AC signal such that said input current will generate said corresponding signal.

18. The method as set forth in claim 15, wherein said operating condition being monitored comprises the condition of said magnetron becoming conductive.

19. The method as set forth in claim 15, wherein said operating condition being monitored comprises the time it takes for said magnetron to start conducting.

20. The method as set forth in claim 15, wherein said microwave oven having a plurality of magnetrons, said step for monitoring further comprises monitoring the condition of said plurality of magnetrons.

21. A microwave oven controller comprising:

means for transforming magnetic flux from an input current variably drawn by said magnetron from an external power source to a corresponding signal, wherein said corresponding signal is proportional to said input signal;

means for converting said corresponding signal from an analog signal to a digital signal;

means for determining the amperage of said input current from said corresponding signal; and

means for monitoring the condition of said magnetron from the determined amperage of said input current; and

wherein

said means for determining the amperage comprises;

means for sampling said corresponding signal; and

means for determining from said means for sampling the highest reading on said input signal having a sinusoidal wave form.

22. A microwave oven controller according to claim 21, wherein said means for transforming comprises:

means for transforming magnetic flux from said input current to a small AC signal;

means for rectifying said small AC signal; and

means for scaling said small AC signal such that said input current will generate said corresponding signal.

23. A microwave oven controller according to claim 21, wherein said operating condition being monitored comprises the condition of said magnetron becoming conductive.

24. A microwave oven controller according to claim 21, wherein said operating condition being monitored comprises the time it takes for said magnetron to start conducting.

25. A microwave controller according to claim 21, wherein said microwave oven has a plurality of magnetrons, said means for monitoring further comprises at least means for monitoring the condition of said plurality of magnetrons.