Adaptive control for a refrigeration system using pulse width modulated duty cycle scroll compressor

• US 6,467,280 B2
• Filed: 06/21/2001
• Issued: 10/22/2002
• Est. Priority Date: 06/07/1995
• Status: Expired due to Term

• Current Assignee: Emerson Climate Technologies Incorporated (Emerson Electric Company)
• Original Assignee: Copeland Corporation LLC (Emerson Electric Company)
• Inventors: Pham, Hung M., Caillat, Jean-Luc M., Singh, Abtar, Bass, Mark
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US09/886,592
• Publication Number:
  US 20010049942A1
• Time in Patent Office: 488 Days
• Field of Search: 621/25, 621/26, 621/27, 621/29, 621/30, 622/281, 622/283, 622/284, 622/285, 621/57, 621/58, 622/31
• US Class Current: 62/126
• CPC Class Codes: A47F 3/04 air-conditioned, refrigerated refrigerators F25D; heating arrangements specially adapted for transparent or reflecting areas H05B3/84
• CPC Class Codes: F04C 18/0215 where only one member is moving
• CPC Class Codes: F04C 2270/015 Controlled or regulated
• CPC Class Codes: F04C 2270/86 Detection
• CPC Class Codes: F04C 23/008 Hermetic pumps
• CPC Class Codes: F04C 27/005 Axial sealings for working fluid
• CPC Class Codes: F04C 28/00 Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
• CPC Class Codes: F04C 28/02 specially adapted for several pumps connected in series or in parallel
• CPC Class Codes: F04C 28/06 specially adapted for stopping, starting, idling or no-load operation
• CPC Class Codes: F04C 28/08 characterised by varying the rotational speed
• CPC Class Codes: F04C 28/22 by changing the eccentricity between cooperating members
• CPC Class Codes: F04C 28/265 being obtained by displacing a lateral sealing face
• CPC Class Codes: F04C 28/28 Safety arrangements; Monitoring
• CPC Class Codes: F25B 1/04 with compressor of rotary type F25B1/005, F25B1/10 take precedence
• CPC Class Codes: F25B 2400/22 Refrigeration systems for supermarkets
• CPC Class Codes: F25B 2600/0261 external to the compressor
• CPC Class Codes: F25B 2700/193 of the compressor
• CPC Class Codes: F25B 2700/1933 Suction pressures
• CPC Class Codes: F25B 2700/2106 of fresh outdoor air
• CPC Class Codes: F25B 2700/2117 of an evaporator
• CPC Class Codes: F25B 2700/21174 : of the refrigerant at the inlet of the evaporator
• CPC Class Codes: F25B 2700/21175 : of the refrigerant at the outlet of the evaporator
• CPC Class Codes: F25B 41/22 : between evaporator and compressor
• CPC Class Codes: F25B 41/35 : by rotary motors, e.g. by stepping motors
• CPC Class Codes: F25B 49/005 : of safety devices F25B49/02 and F25B49/04 take precedence
• CPC Class Codes: F25B 49/022 : Compressor control arrangements
• CPC Class Codes: F25B 5/02 : arranged in parallel
• CPC Class Codes: G05D 23/1909 : whose output amplitude can only take two discrete values
• CPC Class Codes: Y02B 30/70 : Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A diagnostic system includes a controller adapted for coupling to a compressor or electronic stepper regulator valve. The controller produces a variable duty cycle control signal to adjust the capacity of the compressor or valve position of the electronic stepper regulator valve as a function of demand for cooling. The diagnostic system further includes a diagnostic module coupled to the controller for monitoring and comparing the duty cycle with at least one predetermined fault value indicative of a system fault condition and an alert module responsive to the diagnostic module for issuing an alert signal when the duty cycle bears a predetermined relationship to the fault value.

Claims

1. A diagnostic system for a compressor controller, comprising:

a controller adapted for coupling to a compressor, said controller producing a variable duty cycle control signal for adjusting a capacity of said compressor, in which said duty cycle control signal for adjusting a capacity of said compressor, in which said duty cycle is a function of demand for cooling;

a diagnostic module coupled to said controller for monitoring and comparing said duty cycle with at least one predetermined fault value indicative of a system fault condition, wherein said diagnostic module monitors a percentage of sampled error over a defined period of time; and

an alert module responsive to said diagnostic module for issuing an alert signal when said duty cycle bears a predetermined relationship to said fault value.

2. The diagnostic system of claim 1, wherein said diagnostic module monitors and compares at least one of the following conditions:

said capacity of said compressor;

an error value percentage indicative of a percentage of sampled error within an accepted offset range for a defined period of time;

a moving average of said capacity of said compressor for a defined period of time;

a steady state loading percentage set equal to said moving average of said capacity for a defined period of time when said error value percentage is less than fifty percent;

a discharge cooling fluid temperature;

an evaporator coil inlet temperature;

an evaporator coil exit temperature;

a moving average of a difference between said discharge cooling fluid temperature and said evaporator coil inlet temperature;

a moving average of a difference between said evaporator coil exit temperature and said evaporator coil inlet temperature to approximate a superheat value; and

length of time said evaporator coil exit temperature is less than said evaporator coil inlet temperature during a predefined period of time.

3. The diagnostic system of claim 1, wherein said predetermined fault value is an accepted offset range.

4. The diagnostic system of claim 3, wherein said diagnostic module determines an error value percentage indicative of said percentage of sampled error within said accepted offset range for said defined period of time.

5. The diagnostic system of claim 4, wherein said alert module issues an alert signal when said capacity of said compressor is approximately zero percent for approximately ninety percent of said defined period of time and said error value percentage is less than one hundred percent, said alert signal indicating said compressor is over-sized.

6. The diagnostic system of claim 4, wherein said diagnostic module further monitors and compares a superheat value indicative of evaporator superheat.

7. The diagnostic system of claim 6, wherein said alert module issues an alert signal when said capacity of said compressor is approximately one hundred percent for approximately ninety percent of said defined period of time, said error value percentage is approximately zero percent, and said superheat value is approximately greater than 5°

F., said alert signal indicating said compressor is undersized.

8. The diagnostic system of claim 6, wherein said diagnostic module further monitors and compares an evaporator coil inlet temperature value indicative of evaporator coil inlet temperature.

9. The diagnostic system of claim 8, wherein said alert module issues an alert signal when said error value percentage is approximately zero percent, said capacity of said compressor is approximately zero percent for approximately one hundred percent of said defined period of time, said evaporator coil inlet temperature value is less than approximately 32°

F., and said superheat value is approximately greater than 5°

F., said alert signal indicating a solenoid for said compressor is stuck open.

10. The diagnostic system of claim 8, wherein said error value percentage is approximately zero percent, said capacity of said compressor is approximately one hundred percent for approximately one hundred percent of said defined period of time, said evaporator coil inlet temperature value is approximately greater than 32°

F., and said superheat value is approximately greater than 5°

F., said alert signal indicating a solenoid for said compressor is stuck closed.

11. The diagnostic system of claim 8, wherein said diagnostic module further monitors and compares an evaporator coil exit temperature value indicative of evaporator coil exit temperature.

12. The diagnostic system of claim 11, wherein said alert module issues an alert signal when said capacity of said compressor is approximately one hundred percent for approximately one hundred percent of said defined period of time, said error value percentage is approximately zero, said superheat value is approximately less than 5°

F., said evaporator coil inlet temperature value is approximately less than 25°

F., and said evaporator coil exit temperature value is less than said evaporator coil inlet temperature value for greater than fifty percent of said defined period of time, said alert signal indicating that air flow to an evaporator is blocked or evaporator fans are not operating properly.

13. A diagnostic system for a compressor controller, comprising:

a controller adapted for coupling to a compressor, said controller producing a variable duty cycle control signal for adjusting a capacity of said compressor, in which said duty cycle is a function of demand for cooling;

a diagnostic module coupled to said controller for monitoring and comparing said duty cycle with at least one predetermined fault value indicative of a system fault condition;

an alert module responsive to said diagnostic module for issuing an alert signal when said duty cycle bears a predetermined relationship to said fault value, wherein said diagnostic module monitors and compares at least one of the following conditions;

said capacity of said compressor;

an error value percentage indicative of a percentage of sampled error within an accepted offset range for a defined period of time;

a moving average of said capacity of said compressor for a defined period of time;

a steady state loading percentage set equal to said moving average of said capacity for a defined period of time when said error value percentage is less than fifty percent;

a discharge cooling fluid temperature;

a moving average of a difference between said discharge cooling fluid temperature and said evaporator coil inlet temperature;

a moving average of a difference between said evaporator coil exit temperature and said evaporator coil inlet temperature to approximate a superheat value; and

length of time said evaporator coil exit temperature is less than said evaporator coil inlet temperature during a predefined period of time.

14. The diagnostic system of claim 13, wherein said diagnostic module monitors a percentage of sampled error over a defined period of time.

15. The diagnostic system of claim 14, wherein said predetermined fault value is an accepted offset range.

16. The diagnostic system of claim 15, wherein said diagnostic module determines an error value percentage indicative of said percentage of sampled error within said accepted offset range for said defined period of time.

17. The diagnostic system of claim 16, wherein said alert module issues an alert signal when said capacity of said compressor is approximately zero percent for approximately ninety percent of said defined period of time and said error value percentage is less than one hundred percent, said alert signal indicating said compressor is over-sized.

18. The diagnostic system of claim 16, wherein said diagnostic module further monitors and compares a superheat value indicative of evaporator superheat.

19. The diagnostic system of claim 18, wherein said alert module issues an alert signal when said capacity of said compressor is approximately one hundred percent for approximately ninety percent of said defined period of time, said error value percentage is approximately zero percent, and said superheat value is approximately greater than 5°

F., said alert signal indicating said compressor is undersized.

20. The diagnostic system of claim 18, wherein said diagnostic module further monitors and compares an evaporator coil inlet temperature value indicative of evaporator coil inlet temperature.

21. The diagnostic system of claim 20, wherein said alert module issues an alert signal when said error value percentage is approximately zero percent, said capacity of said compressor is approximately zero percent for approximately one hundred percent of said defined period of time, said evaporator coil inlet temperature value is less than approximately 32°

F., and said superheat value is approximately greater than 5°

F., said alert signal indicating a solenoid for said compressor is stuck open.

22. The diagnostic system of claim 20, wherein said error value percentage is approximately zero percent, said capacity of said compressor is approximately one hundred percent for approximately one hundred percent of said defined period of time, said evaporator coil inlet temperature value is approximately greater than 32°

F., and said superheat value is approximately greater than 5°

F., said alert signal indicating a solenoid for said compressor is stuck closed.

23. The diagnostic system of claim 20 wherein said diagnostic module further monitors and compares an evaporator coil exit temperature value indicative of evaporator coil exit temperature.

24. The diagnostic system of claim 23, wherein said alert module issues an alert signal when said capacity of said compressor is approximately one hundred percent for approximately one hundred percent of said defined period of time, said error value percentage is approximately zero, said superheat value is approximately less than 5°

F., said evaporator coil inlet temperature value is approximately less than 25°

F., and said evaporator coil exit temperature value is less than said evaporator coil inlet temperature value for greater than fifty percent of said defined period of time, said alert signal indicating that air flow to an evaporator is blocked or evaporator fans are not operating properly.