Voltage compensation in combination oven using radiant and microwave energy

• US 6,696,676 B1
• Filed: 01/11/2000
• Issued: 02/24/2004
• Est. Priority Date: 03/30/1999
• Status: Expired due to Term

• Current Assignee: Haier US Appliance Solutions, Inc. DBA GE Appliances (Haier Group Company)
• Original Assignee: General Electric Company
• Inventors: Graves, Todd Vincent, Head, Jesse Spalding, Kill, Dennis Patrick, Smith, Charles Ray
• Primary Examiner(s): Leung, Philip H.
• Application Number:
  US09/481,064
• Time in Patent Office: 1,505 Days
• Field of Search: 219/716, 219/718, 219/717, 219/719, 219/702, 219/685, 219/681, 219/482, 219/483, 219/486, 219/492, 219/497, 993/25, 993/27, 993/32, 994/51, 323/299, 361/79, 361/86, 361/91, 361/92
• US Class Current: 219/716
• CPC Class Codes: F24C 7/087 of electric circuits regulating heat
• CPC Class Codes: H05B 6/645 using temperature sensors
• CPC Class Codes: H05B 6/6482 combined with radiant heating, e.g. infrared heating

Abstract

An oven includes both radiant cooking elements and a microwave cooking element that are controlled to reduce cooking time in relation to known radiant ovens. The oven is operable in a speed cooking mode utilizing radiant and microwave cooking elements, a microwave cooking mode utilizing only the magnetron, and a radiant cooking mode utilizing only radiant lamps. In addition, and using a time adjustment algorithm, the total energy into the food is maintained constant for input voltages in a range between about 108 Volts and 132 Volts to suitably cook food even when the input voltage varies.

Claims

1. A method for maintaining a constant energy into food being cooked in an oven including a microwave cooking unit, at least one radiant cooking unit, a control panel and a microcomputer for executing desired cooking operations of the microwave cooking unit and radiant cooking unit in accordance with selected user inputs to the control panel, the user inputs including a cooking time and cooking power levels for the respective cooking units, the oven connected to a power source including an input voltage to the oven, said method comprising the steps of:

determining a magnitude of the input voltage to the oven;

comparing the determined input voltage to a nominal input voltage;

calculating a delta voltage ratio;

determining a time adjustment value comprising the steps of;

squaring the delta voltage ratio to determine a squared voltage ratio;

multiplying the squared voltage ratio by 5; and

subtracting 1.5 times the delta voltage ratio;

adding the time adjustment value to the user selected cooking time to determine an adjusted cooking time; and

operating the microwave cooking unit and radiant cooking unit for the adjusted cooking time.

2. A method in accordance with claim 1 wherein the step of determined a delta voltage ratio comprises the steps of:

subtracting the nominal voltage from the determined input voltage to determine a voltage difference; and

dividing the voltage difference by the nominal voltage.

3. A method in accordance with claim 2 wherein the nominal voltage is 120V.

4. A method in accordance with claim 1 wherein said step of determining a time adjustment value comprises the step of approximating a time adjustment value by multiplying the input cooking time by the product of a voltage constant and the delta voltage ratio where the voltage constant is −

2 when the input voltage is less than about 120 volts and the voltage constant is −

1 when tie input voltage is greater than about 120 volts.

5. A method in accordance with claim 1 wherein the step of operating the microwave cooking unit and radiant cooking unit comprises the step of:

selecting a respective duty cycle target on time for the microwave cooking unit and radiant cooking unit according to user selected power level inputs; and

energizing the respective cooking units for the respective target on times during a duty cycle;

de-energizing the respective cooking units for a respective remainder of the duty cycle, and

repeating the duty cycles until the adjusted cooking time has elapsed.

6. A method in accordance with claim 5 wherein the duty cycle is approximately 32 seconds.

7. A method in accordance with claim 5 further comprising the step of adjusting the target on time of the radiant cooking unit to accommodate soft start operation.

8. A method in accordance with claim 5 wherein the step of repeating duty cycles until the adjusted time has elapsed comprises the steps of executing a partial duty cycle when the completion of a complete duty cycle would exceed the adjusted time.

9. A method in accordance with claim 1 wherein the input voltage fluctuates from about 108V to about 132V.

10. A method in accordance with claim 1 wherein the microcomputer includes a memory loaded with predetermined time adjustment values corresponding to a range of input voltages, said step of adjusting the cooking time comprising the step of selecting a time adjustment value from the memory corresponding to the determined input voltage.

11. A combination microwave/radiant oven for connection to a power source including an input voltage, said oven comprising:

a cooking cavity;

a microcomputer programmed to determine a magnitude of the input voltage and to determine a time adjustment value according to a relationship Δ

T/T0=X(Δ

V/V0) where X=−

2 when the input voltage is less than about 120V, and X=−

1 when the input voltage is greater than 120V;

a microwave cooking unit for deliver microwave energy to said cooking cavity and operatively connected to the microcomputer;

at least one radiant cooking unit for delivering radiant energy to said cooking cavity and operatively connected to the microcomputer; and

said microcomputer operating said microwave cooking unit and said at least one radiant cooking unit in accordance with a selected cooking time and selected cooking power levels for the respective cooking units, and said microcomputer programmed to adjust the selected cooking time based on said time adjustment value to ensure delivery of a constant energy into said cooking cavity despite fluctuation in the input voltage.

12. A combination oven m accordance with claim 13 wherein said microcomputer is further programmed to determine a time adjustment value according to a relationship

13. A combination oven in accordance with claim 11 wherein said microcomputer comprises a memory, said microcomputer programmed to select a predetermined time adjustment value from a look-up table of time adjustment values stored in said memory.

14. A combination oven in accordance with claim 11 wherein said nominal voltage is 120V.

15. A combination oven in accordance with claim 11 wherein said microcomputer is programmed to deliver a constant stream of energy into said cooking cavity when the input voltage fluctuates from about 108V to about 132V.

16. A combination microwave/radiant oven for connection to a power source including an input voltage that fluctuates from about 108V to about 132V, said oven comprising:

a cooking cavity;

a microcomputer;

a microwave cooking unit for delivering microwave energy to said cooking cavity and operatively connected to the microcomputer;

at least one radiant cooking unit for delivering radiant energy to said cooking cavity and operatively connected to the microcomputer;

a control panel operatively coupled to said microcomputer for accepting a user selected cooking time input and selected cooking power levels for the respective cooking units;

said microcomputer operating said microwave cooking unit and said at least one radiant cooking unit in accordance with said user selected cooking time and power levels; and

said microcomputer programmed to determine the input voltage and adjust selected cooking time by a time adjustment value determined by the relationship