Power modulator for infrared conveyor oven

Abstract

A system and method to control the power supplied to heating elements of a conveyor oven. The conveyor oven includes a plurality of heating elements to evenly distribute heat in an oven compartment. During peak-loads, the current draw of the heating elements may exceed available power of a power supply. Therefore, a system and method to reduce the total current draw of the plurality of heating elements is provided. The system includes a controller configured to perform the methods disclosed herein. The methods effectively lower the total current draw by rapidly cycling a plurality of relays connected to each of the plurality of heating elements to achieve even distribution of heat and reduced current draw during peak-loads.

What is claimed is: 
     
         1 . A conveyor oven comprising:
 an oven compartment;   a conveyor extending through the oven compartment;   a motor that drives the conveyor;   a first heating element;   a first relay that controls a current flow to the first heating element;   a power supply that receives external power and distributes power to components within the conveyor oven; and   a controller connected to the power supply and to the first relay, the controller configured to send a heating element control signal to the first relay, the heating element control signal pulsed such that the first relay is repeatedly actuated to reduce an average current to the first heating element.   
     
     
         2 . The conveyor oven of  claim 1 , further comprising:
 a plurality of zones, each zone located in a portion of the oven compartment;   a plurality of heating elements each heating element associated with one of the plurality of zones;   a plurality of relays, each relay connected to each of the plurality of heating elements;   wherein the controller selectively actuates each of the plurality of relays such that at least one relay is energized and at least one relay is de-energized during heating of the oven compartment.   
     
     
         3 . The conveyor oven of  claim 1 , further comprising:
 a second heating element and a third heating element;   a second relay connected to the second heating element and a third relay connected to the third heating element;   wherein the controller is configured to
 actuate the first relay, the second relay, and the third relay such that the second heating element and the third heating element are energized for a first period of time during which the first heating element is de-energized; 
 actuate the second relay to de-energize the second heating element for a second period of time; 
 actuate the first relay to energize the first heating element for a third period of time; 
 actuate the third relay to de-energize the third heating element for a fourth period of time; 
 actuate the second relay to energize the second heating element for a fourth period of time; 
 actuate the first relay to de-energize the first heating element for a fifth period of time; and 
 actuate the third relay to energize the third heating element for a sixth period of time. 
   
     
     
         4 . The conveyor oven of  claim 3 , wherein each of the second, fourth, and sixth periods of time, are less than each of the first, third, and fifth periods of time. 
     
     
         5 . The conveyor oven of  claim 4 , wherein each of the first, third, and fifth periods of time are equal and each of the second, fourth, and sixth periods of time are equal, and wherein the first, the second, the third, the fourth, the fifth, and the sixth periods of time cumulatively constitute one cycle, the one cycle repeating continuously during heating of the oven compartment. 
     
     
         6 . The conveyor oven of  claim 1 , further comprising:
 a second heating element, a third heating element, and a fourth heating element;   a second relay connected to the second heating element, a third relay connected to the third heating element, and a fourth relay connected to the fourth heating element;   wherein the controller is configured to
 actuate the first relay, the second relay, the third relay, and the fourth relay such that the second heating element, the third heating element, and the fourth heating element are energized for a first period of time while the first heating element is de-energized; 
 actuate the first relay, the second relay, the third relay, and the fourth relay such that the second heating element is de-energized, the third heating element is energized, and the fourth heating element is energized for a second period of time while the first heating element is de-energized; 
 actuate the first relay, the second relay, the third relay, and the fourth relay such that the first heating element is energized, the third heating element is energized, and the fourth heating element is energized for a third period of time while the second heating element is de-energized; 
 actuate the first relay, the second relay, the third relay, and the fourth relay such that the first heating element is energized, the third heating element is de-energized, and the fourth heating element is energized for a fourth period of time while the second heating element is de-energized; 
 actuate the first relay, the second relay, the third relay, and the fourth relay such that the first heating element is energized, the second heating element is energized, and the fourth heating element is energized for a fifth period of time while the third heating element is de-energized; 
 actuate the first relay, the second relay, the third relay, and the fourth relay and such that the first heating element is energized, the second heating element is energized, the fourth heating element is de-energized for a sixth period of time while the third heating element is de-energized; 
 actuate the first relay, the second relay, the third relay, and the fourth relay such that the first heating element is energized, the second heating element is energized, the third heating element is energized for a seventh period of time while the fourth heating element is de-energized; and 
 actuate the first relay, the second relay, the third relay, and the fourth relay such that the first heating element is de-energized, the second heating element is energized, and the third heating element is energized for an eighth period of time while the fourth heating element is de-energized. 
   
     
     
         7 . The conveyor oven of  claim 1 , wherein the heating elements are infrared heating elements. 
     
     
         8 . The conveyor oven of  claim 1 , wherein the relays are solid-state relays. 
     
     
         9 . The conveyor oven of  claim 1 , wherein the external power is single-phase power. 
     
     
         10 . The conveyor oven of  claim 1 , wherein the external power is three-phase power. 
     
     
         11 . The conveyor oven of  claim 3 , wherein
 an input of the first relay is connected to a first phase of the three-phase power, an output of the first relay is connected to a first terminal of the first heating element, and a second terminal of the first heating element is connected to a second phase of the three-phase power;   an input of the second relay is connected to the second phase of the three-phase power, an output of the second relay is connected to a first terminal of the second heating element, and a second terminal of the second heating element is connected to a third phase of the three-phase power; and   an input of the third relay is connected to a third phase of the three-phase power, an output of the third relay is connected to a first terminal of the third heating element, and a second terminal of the third heating element is connected to a first phase of the three-phase power.   
     
     
         12 . The conveyor oven of  claim 1 , wherein the controller includes a user interface, the user interface configured to
 receive an input from a user;   display a status of the conveyor oven to the user; and   transmit a control signal to the controller indicative of a desired temperature setpoint of the oven compartment,   wherein the controller detects a temperature of the conveyor oven, and   wherein the controller transmits the heating element control signal to the first relay based at least in part on the control signal and the temperature of the conveyor oven.   
     
     
         13 . A method for controlling a conveyor oven, the conveyor oven including an oven compartment, a first heating element, a second heating element, and a third heating element, a first relay connected to the first heating element, a second relay connected to the second heating element, a third relay connected to the third heating element, and a controller, the method comprising:
 actuating the first relay, the second relay, and the third relay such that the second heating element and the third heating element are energized for a first period of time while the first heating element is de-energized;   actuating the first relay, the second relay, and the third relay such that the second heating element is de-energized and the third heating element is energized for a second period of time while the first heating element is de-energized;   actuating the first relay, the second relay, and the third relay such that the first heating element and the third heating element are energized for a third period of time while the second heating element is de-energized;   actuating the first relay, the second relay, and the third relay such that the first heating element is energized and the third heating element is de-energized for a fourth period of time while the second heating element is de-energized;   actuating the first relay, the second relay, and the third relay such that the first heating element and the third heating element are energized for a fifth period of time while the third heating element is de-energized; and   actuating the first relay, the second relay, and the third relay such that the first heating element is de-energized and the second heating element is energized for a sixth period of time while the third heating element is de-energized.   
     
     
         14 . The method of  claim 13 , wherein
 the first period, the third period, and the fifth period of time are equal,   the second period, the fourth period, and the sixth period of time are equal,   each of the first period, the third period, and the fifth period of time are greater than each of the first period, the third period, and the fifth period of time; and   the first period, the second period, the third period, the fourth period, the fifth period, and the sixth period of time cumulatively constitute one cycle, the one cycle continuously repeating during heating of the oven compartment.   
     
     
         15 . The method of  claim 13 , wherein when an input signal from a thermocouple indicates that the conveyor oven is at a temperature equal to or greater than a temperature setpoint determined by the controller, the controller ceases to perform the method. 
     
     
         16 . The method of  claim 13 , wherein the heating elements are infrared heating elements. 
     
     
         17 . The method of  claim 13 , wherein the relays are solid-state relays. 
     
     
         18 . The method of  claim 13 , wherein the external power is single-phase power. 
     
     
         19 . The method of  claim 13 , wherein the external power is three-phase power.