Heater/blower unit with load control

• US 20020030048A1
• Filed: 10/03/2001
• Published: 03/14/2002
• Est. Priority Date: 01/18/2000
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: Arizant Healthcare Inc. (3M Company)
• Inventors: Fraley, Peter Donald, Ziaimehr, Allen Hamid, Van Duren, Albert Philip
• Granted Patent: US 6,541,740 B2
• Time in Patent Office: Days
• US Class Current: 219/486
• CPC Class Codes: G05D 23/1913 delivering a series of pulses
• CPC Class Codes: H05B 1/0277 Electric radiators

Abstract

A substantially constant load impedance electrical heater has been provided. The heater is comprised of two sections, a first heater and a second heater. The first heater is continuously “on” to provide the bulk of the heat. A second heater is selectively engaged to provide slightly more heat to the medium, heating the medium to the desired temperature. The output temperature of the heated medium is maintained by controlling the duty cycle of the second heater. More drastic changes in temperature are accomplished by changing the power continuously dissipated by the first heater. The greatest heating control is obtained by defining the first and second heaters as subsets from a bank of selectable heater elements. A method of minimizing fluctuations in the loading of a high-wattage electrical device is also provided.

Claims

1. A heater comprising:

a first heater, to continuously heat a medium to a first temperature; and

a second heater, to intermittently heat the medium, in combination with said first heater, to a second temperature, greater than the first temperature.

2. The heater of claim 1 in which said first heater dissipates a first peak power, in which said combination of first and second heaters dissipates a second peak power, greater than the first peak power.

3. The heater of claim 2 in which said second heater dissipates a third peak power, which is the difference between the first and second peak powers, the third peak power being less than the first peak power.

4. The heater of claim 3 in which said second heater dissipates less than approximately 200 watts of peak power.

5. The heater of claim 3 further comprising:

a controller having an output to provide temperature control commands; and

in which said second heater has an input connected to said controller, said second heater varying the intermittent dissipation of power in response to commands from said controller.

6. The heater of claim 5 in which said controller provides temperature commands at a first duty cycle rate of modulated pulse widths;

and

in which said second heater dissipates power in response to the first duty cycle pulse-width modulation.

7. The heater of claim 5 in which said controller has an input to receive temperature information, and further comprising:

a first temperature sensor to measure the second temperature, said first temperature sensor having an output, to provide second temperature information, connected to the input of said controller;

in which said controller provides temperature control commands in response to the second temperature information; and

in which said second heater varies the intermittent dissipation of power in response to commands from said controller.

8. The heater of claim 7 in which said first heater includes a plurality of elements to provide a selectable first peak power, said first heater having an input to receive first temperature selection commands to select the first peak power;

in which said controller has an output connected to said first heater input to provide temperature control commands; and

in which said first heater dissipates a selected first peak power in response to temperature control commands from said controller.

9. The heater of claim 8 in which said controller output provides first temperature control commands which vary with respect to time;

and

in which said first heater dynamically varies the first peak power in response to said controller output temperature commands.

10. The heater of claim 9 in which said controller calculates the derivative of the second temperature information and provides temperature control commands in response to a calculation of the derivative.

11. The heater of claim 9 in which said controller has a plurality of inputs, and further comprising:

a second sensor, to measure the medium input temperature, having an output connected to the input of said controller to provide temperature information;

a set-point control to select the second temperature, said set-point control having an output connected to an input of said controller to supply temperature information;

an electrical power source having a line voltage;

a line voltage sensor to measure the line voltage of said electrical power source, said line voltage sensor having an output connected to an input of said controller to provide voltage information;

in which said controller provides temperature control commands in response to the information from said first sensor, said second sensor, said set-point control, and said line voltage sensor; and

in which said plurality of heater elements vary the power dissipated in response to temperature control commands from said controller.

12. The heater of claim 9 comprising:

a plurality of selectably connectable heater elements;

in which said first heater is selected from a first combination of said plurality of heater elements; and

in which the combination of said first and second heaters is selected from a second combination of said plurality of heater elements.

13. The heater of claim 12 in which said plurality of selectably connectable heater elements includes:

a first heater element dissipating a peak power;

a second heater element dissipating a peak power greater than that dissipated by said first heater element;

a third heater element dissipating a peak power, greater than that dissipated by said second heater element;

in which said first heater is selected from the group consisting of no heater element, said first heater element, said second heater element, and said third heater element; and

in which said second heater is selected from the group consisting of said first, second, and third heater elements.

14. The heater of claim 13 in which the peak power of said third heater element is approximately twice as great as the peak power of said second heater element, and in which the peak power of said second heater element is approximately twice as great as the peak power of said first heater element.

15. The heater of claim 12 in which the combination of said first and second heaters dissipates a second peak power no more than approximately 200 watts greater than the first peak power dissipated by said first heater.

16. The heater of claim 12 in which said controller provides temperature control commands generated by a proportional-integral-derivative (PID) formula responsive to the controller inputs;

and

in which said plurality of heater elements vary the power dissipated in response to the temperature control commands from said controller.

17. The heater of claim 12 in which said first heater first combination of said plurality of heater elements varies dynamically;

and

in which said second heater second combination of said plurality of heater elements varies dynamically.

18. The heater of claim 17 in which the temperature control commands provided by said controller include a two-part digital word;

in which each heater element of said plurality of heater elements is selected in response to a bit in the first part of the digital word; and

in which the intermittent occurrence of the second peak power is responsive to the second part of the digital word.

19. The heater of claim 7 in which said controller has a plurality of inputs, and further comprising:

a heater hose having a proximal end connected to the output of said heater, and a distal end to deliver the heated medium;

a heater input to accept the medium, at a third temperature, to be heated;

a second temperature sensor to measure the third temperature of the medium at said heater input, said second temperature sensor having an output connected to said controller to provide third temperature information;

in which said first temperature sensor is located at the proximal end of said heater hose;

in which said controller varies the temperature control commands in response to the third temperature information.

20. The heater of claim 1 wherein the medium is air, and further comprising:

a blower to deliver air to said first and second heaters.

21. A method for heating a medium comprising:

continuously dissipating a first peak power into the medium; and

intermittently dissipating an additional peak power, in combination with the first peak power, into the medium.

22. The method of claim 21 in which the dissipation of the first peak power includes selecting the first peak power from a plurality of peak power levels.

23. The method of claim 21 in which the combination of the first peak power and the intermittent peak power is a second peak power, with the intermittent additional peak power being a third peak power level, and in which the intermittent dissipation of additional peak power includes selecting the second peak power so as to minimize the third peak power.

24. The method of claim 23 in which the third peak power is less than approximately 200 watts.

25. The method of claim 23 further comprising:

in response to the dissipation of the first peak power, generating substantially a desired temperature in the medium; and

in response to the intermittent dissipation of an additional peak power, generating an output temperature that is the desired medium output temperature.

26. The method of claim 25 further comprising:

measuring the desired output temperature over time; and

in which the intermittent dissipation of an additional peak power includes varying the intermittence of the second peak power in response to the measured temperature.

27. The method of claim 26 in which the dissipation of the first peak power includes the first peak power level being selectable, and includes selecting the first peak power level in response to changes in the desired output temperature over time.

28. The method as in claim 27 wherein a power supply is provided, and further comprising:

measuring the medium input temperature;

measuring the power supply voltage;

selecting the desired medium output temperature;

in which the dissipation of the first peak power includes selecting from the plurality of heating elements to generate a first peak power levels in response to the measurement of the power supply voltage, the medium input temperature, the medium output temperature and the selection of the desired medium output temperature; and

in which the intermittent dissipation of an additional peak power includes varying the intermittence of the second peak power in response to the measurement of the power supply voltage, the medium input temperature, the medium output temperature, and the selection of the desired medium output temperature.

29. The method of claim 27 wherein a plurality of heating elements are provided;

in which the dissipation of the first peak power includes selecting a first combination of the plurality of heating elements to generate the first peak power; and

in which the intermittent dissipation of an additional peak power includes selecting a second combination of the plurality of heating elements to generate the second peak power.

30. The method of claim 29 wherein at least first, second, and third heating elements are provided, wherein the third heating element dissipates a peak power greater than that dissipated by the second heating element, and the second heater dissipates a peak power greater than that dissipated by the first heating element, in which the dissipation of the first peak power includes generating the first peak power from heating elements selected from the group consisting of the no heating elements, first, second, and third heating elements, and in which the intermittent dissipation of an additional peak power includes generating the second peak power from heating elements selected from the group consisting the first, second, and third heating elements.

31. The method of claim 30 wherein a controller is provided, and wherein the plurality of heating elements are selectively connectable to a power supply voltage, and further comprising:

selectably connecting the plurality of heating elements to the power supply voltage in response to the generation of temperature control commands by the controller;

in which the dissipation of the first peak power includes selecting from the plurality of heating elements to generate first peak power levels in response to the temperature control commands; and

in which the intermittent dissipation of an additional peak power includes selecting from the plurality of heating elements to generate second peak power levels and varying the intermittence of the second peak power in response to the temperature control commands.

32. The method of claim 31 in which the generation temperature control commands includes creating a two-part digital word, where the first part includes a plurality of bits, with each bit corresponding to a heating element of the plurality of heating elements, and where the second part of the digital word creates a timing pattern;

in which the dissipation of the first peak power includes selecting from the plurality of heating elements to generate a first peak power levels in response to the first part of the digital word; and

in which the intermittent dissipation of an additional peak power includes varying the intermittence of the second peak power in response to the second part of the digital word.

33. The method of claim 32 wherein the controller has a plurality of inputs, and further comprising:

providing temperature related variables to the controller including the medium output temperature and the desired temperature set-point; and

generating the temperature control word in response to the temperature related variable using a proportional-integral-derivative (PID) algorithm.

35. The method of claim 34 in which the dissipation of a variable peak power includes alternately dissipating a first peak power, and a second peak power, greater than the first peak power.

36. The method of claim 35 in which the dissipation of a variable peak power includes varying the first duty cycle;

and

in which the heating of the medium includes maintaining the constant output temperature in response to varying the first duty cycle.

37. The method of claim 36 in which the dissipation of a variable peak power includes the difference between the first and second peak powers being less than 200 watts.

39. The method of claim 38 further comprising:

providing a medium to be heated;

measuring the temperature of the heated medium; and

generating the digital word in responsive to the measurement of the heated medium.

40. The method of claim 39 in which the selection of a peak power dissipation includes varying the power between a first and second peak power;

and

in which the selection of a peak power time duration includes selecting a first duration for the first peak power and a second duration for the second peak power.

41. The method of claim 40 wherein a first plurality of selectively engagable heating elements is provided;

and

in which the generation of the digital word first part includes a first plurality of bits, with each bit corresponding to a heating element, and the generation of the second part includes a second plurality of bits, the sum of which defines a timing pattern;

in which the selection of the first peak power includes engaging each heating element in response to the corresponding bit in the digital word first part; and

in which the first duration of the first peak power includes engaging heating elements for a duration responsive to the sum of the bits in the digital word second part.

42. The method of claim 40 in which the selection of the peak power includes the difference between the first and second peak power being less than 200 watts.

34. A method for minimizing fluctuations in power consumption comprising:

dissipating a variable peak power into a medium at a first duty cycle; and

in response to dissipating a variable peak power, heating a medium to a constant temperature.

38. A method for programmably controlling a heater comprising:

generating a digital word including a first part and a second part;

selecting a peak power dissipation in response to the digital word first part; and

selecting the peak power time duration in response to the digital word second part.