Apparatus and method for intelligent control of the fan speed of air-cooled condensers

• US 6,594,554 B1
• Filed: 07/11/2000
• Issued: 07/15/2003
• Est. Priority Date: 07/28/1999
• Status: Expired due to Fees

• Current Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Huisman, Willem, West, Jonathan D, Seem, John E
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): CABRERA, ZOILA E
• Application Number:
  US09/613,844
• Time in Patent Office: 1,099 Days
• Field of Search: 700/276, 700/275, 700/278, 700/282, 621/81, 621/83
• US Class Current: 700/276
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/52 Indication arrangements, e.g. displays
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: F25B 2600/111 of condenser fans
• CPC Class Codes: F25B 2600/112 of evaporator fans
• CPC Class Codes: F25B 2600/19 Refrigerant outlet condenser temperature
• CPC Class Codes: F25B 2700/2116 of a condenser
• CPC Class Codes: F25B 49/027 Condenser control arrangements
• CPC Class Codes: G05D 23/1913 delivering a series of pulses
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A refrigeration system (10) has a compressor (12) that forces a refrigerant to flow in a loop between an evaporator (17) and a condenser (16). The present method controls the speed of a condenser fan (16) in response to the condenser temperature. In a first control state, the speed of the fan (16) is varied in response to the condenser temperature. In a second state, the fan (16) is turned on and off by a pulse width modulated signal that has a duty cycle which varies in response to the condenser temperature. A transition occurs from the first state to the second state when the fan (16) operates at the slowest possible speed for a predetermined period while the condenser temperature is below a desired value. A transition occurs from the second state to the first state when the duty cycle is at 100% for a given period and the condenser temperature is above the desired value.

Claims

1. A method for operating a fan which produces an air flow across a condenser of a refrigeration system, said method comprising:

sensing a temperature of the condenser to produce a temperature measurement;

operating the fan in a first state of operation in which speed of the fan is varied in response to a comparison of the temperature measurement to a temperature set point;

operating the fan in a second state of operation in which the fan is pulsed on and off thereby defining a duty cycle of operation;

making a transition from the first state to the second state upon the occurrence of a first transition condition; and

making a transition from the second state to the first state upon the occurrence of a second transition condition,

wherein the first transition condition occurs at least in part based on a comparison of the speed of the fan to a predefined speed level and the second transition condition occurs at least in part based on a comparison of the duty cycle of the fan to a given value.

2. The method as recited in claim 1 wherein the second transition condition occurs when the duty cycle is above the given value for a given period of time.

3. The method as recited in claim 1 wherein operating the fan in the first state of operation employs proportional integral control.

4. The method as recited in claim 3, wherein the proportional integral control is tuned with a pattern recognition adaptive control algorithm.

5. The method as recited in claim 1 wherein operating the fan in the second state of operation employs proportional integral control.

6. The method as recited in claim 1 wherein operating the fan In the second state of operation employs proportional integral control in which a gain parameter and an integral time are determined in response to a pattern recognition adaptive control algorithm.

7. A method for operating a fan which produces an air flow across a condenser of a refrigeration system, said method comprising:

sensing a temperature of the condenser to produce a temperature measurement;

operating the fan in a first state of operation in which speed of the fan is varied in response to a comparison of the temperature measurement to a temperature set point;

operating the fan in a second state of operation in which the fan is pulsed on and off thereby defining a duty cycle of operation;

making a transition from the first state to the second state upon the occurrence of a first transition condition; and

making a transition from the second state to the first state upon the occurrence of a second transition condition,

wherein the first transition condition occurs when the fan has operated below a predefined speed level for a predetermined period of time.

8. A method for operating a fan which produces an air flow across a condenser of a refrigeration system, said method comprising:

sensing a temperature of the condenser to produce a temperature measurement;

operating the fan in a first state of operation in which speed of the fan is varied in response to a comparison of the temperature measurement to a temperature set point;

operating the fan in a second state of operation in which the fan is pulsed on and off thereby defining a duty cycle of operation;

making a transition from the first state to the second state upon the occurrence of a first transition condition; and

making a transition from the second state to the first state upon the occurrence of a second transition condition,

wherein the first transition condition occurs when the fan has operated below a predefined speed level for a predetermined period of time and the temperature measurement is below the temperature set point.

9. A method for operating a fan which produces an air flow across a condenser of a refrigeration system, said method comprising:

sensing a temperature of the condenser to produce a temperature measurement;

operating the fan in a first state of operation in which speed of the fan is varied in response to a comparison of the temperature measurement to a temperature set point;

operating the fan in a second state of operation in which the fan is pulsed on and off thereby defining a duty cycle of operation;

making a transition from the first state to the second state upon the occurrence of a first transition condition; and

making a transition from the second state to the first state upon the occurrence of a second transition condition,

wherein the second transition condition occurs when the duty cycle is above a given value for the given period of time, and wherein the given value is 100%.

10. A method for operating a fan which produces an air flow across a condenser of a refrigeration system, said method comprising:

sensing a temperature of the condenser to produce a temperature measurement;

operating the fan in a first state of operation in which speed of the fan is varied in response to a comparison of the temperature measurement to a temperature set point;

operating the fan in a second state of operation in which the fan is pulsed on and off thereby defining a duty cycle of operation;

making a transition from the first state to the second state upon the occurrence of a first transition condition; and

making a transition from the second state to the first state upon the occurrence of a second transition condition,

wherein the second transition condition occurs when the duty cycle is above a given value for the given period of time and the temperature measurement is above the temperature set point.

11. A method for operating a fan which produces an air flow across a condenser of a refrigeration system, said method comprising:

sensing a temperature of the condenser to produce a temperature measurement;

operating the fan in a first state of operation in which speed of the fan is varied in response to a comparison of the temperature measurement to a temperature set point;

operating the fan in a second state of operation in which the fan is pulsed on and off thereby defining a duty cycle of operation;

making a transition from the first state to the second state upon the occurrence of a first transition condition; and

making a transition from the second state to the first state upon the occurrence of a second transition condition,

wherein making a transition from the first state to the second state initially sets the duty cycle of the fan to 100%.

12. A method for operating a fan which produces an air flow across a condenser of a refrigeration system, said method comprising:

sensing a temperature of the condenser to produce a temperature measurement;

operating the fan in a first state of operation in which speed of the fan is varied in response to a comparison of the temperature measurement to a temperature set point;

operating the fan in a second state of operation in which the fan is pulsed on and off thereby defining a duty cycle of operation;

making a transition from the first state to the second state upon the occurrence of a first transition condition; and

making a transition from the second state to the first state upon the occurrence of a second transition condition,

wherein making a transition from the second state to the first state initially operates the fan at a minimum speed at which the fan can operate.

13. A method for operating a fan which produces an air flow across a condenser of a refrigeration system, said method comprising:

sensing a temperature of the condenser to produce a temperature measurement;

operating the fan in a first state of operation in which speed of the fan is varied in response to a comparison of the temperature measurement to a temperature set point;

operating the fan in a second state of operation in which the fan is pulsed on and off thereby defining a duty cycle of operation;

making a transition from the first state to the second state upon the occurrence of a first transition condition; and

making a transition from the second state to the first state upon the occurrence of a second transition condition,

wherein in the second state the fan is operated at a minimum speed at which the fan can operate.

14. A method for operating a fan which produces an air flow across a condenser of a refrigeration system, said method comprising:

sensing a temperature of the condenser to produce a temperature measurement;

operating the fan in a first state of operation in which speed of the fan is varied in response to a comparison of the temperature measurement to a temperature set point;

operating the fan in a second state of operation in which the fan is pulsed on and off thereby defining a duty cycle of operation;

making a transition from the first state to the second state upon the occurrence of a first transition condition; and

making a transition from the second state to the first state upon the occurrence of a second transition condition,

said method further comprising operating the fan in a start-up state upon starting the refrigeration system, the start-up state has a first sub-state, a second sub-state and a third sub-state, wherein,

when the temperature measurement is greater than a predefined temperature upon starting, operating in the first sub-state in which the fan is operated at a predefined speed which is determined from previous operation in the first state;

when the temperature measurement is less than the predefined temperature upon starting, operating in the second sub-state in which the fan is operated at a given speed;

making a transition from the first sub-state to the third sub-state after a warm-up period of time;

making a transition from the second sub-state to one of the third sub-state and the first state upon an occurrence of a third transition condition;

operating in the third sub-state in which the fan is operated at the predefined speed; and

making a transition from the third sub-state to the first state upon an occurrence of a fourth transition condition.

15. The method as recited in claim 14 wherein further comprising while operating in the first state deriving an average speed of the fan (16), wherein the average speed is the predefined speed employed in the first sub-state.

16. The method as recited in claim 15 wherein deriving an average speed of the fan (16) utilizes an exponentially weighted moving average.

17. The method as recited in claim 14 wherein the given speed is the minimum speed at which the fan (16) can operate.

18. The method as recited in claim 14 wherein making a transition from the second sub-state occurs to the third sub-state when the temperature measurement is greater than the predefined temperature for an interval of time, and occurs to the first state after a start-up interval of time.

19. The method as recited in claim 14 wherein the fourth transition condition is selected from a group consisting of operation being in the start-up state for a start-up interval of time, the temperature measurement is greater than the temperature set point, and a negative rate of change in the temperature measurement.