Control system for an air conditioning/refrigeration system

• US 5,284,026 A
• Filed: 02/26/1993
• Issued: 02/08/1994
• Est. Priority Date: 03/04/1992
• Status: Expired due to Term

• Current Assignee: Ecoair Corp.
• Original Assignee: Ecoair Corp.
• Inventors: Powell, James W.
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US08/023,690
• Time in Patent Office: 347 Days
• Field of Search: 62/228.1, 62/228.3, 62/228.4, 62/209, 62/217, 62/208, 62/203, 62/204, 62/226
• US Class Current: 62/209
• CPC Class Codes: F04D 27/0261 by varying driving speed
• CPC Class Codes: F24F 1/00 Room units for air-conditioning, e.g. separate or self-contained units or units receiving primary air from a central station
• CPC Class Codes: F24F 11/00 Control or safety arrangements
• 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 11/32 Responding to malfunctions or emergencies
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/64 using pre-stored data
• CPC Class Codes: F24F 11/84 using valves
• CPC Class Codes: F24F 11/86 by controlling compressors within refrigeration or heat pump circuits
• CPC Class Codes: F24F 11/871 by controlling outdoor fans
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2140/00 Control inputs relating to system states
• CPC Class Codes: F24F 2140/12 Heat-exchange fluid pressure
• CPC Class Codes: F24F 2140/50 Load
• CPC Class Codes: F24F 2221/56 Cooling being a secondary aspect
• CPC Class Codes: F25B 2600/021 Inverters therefor
• CPC Class Codes: F25B 2600/21 Refrigerant outlet evaporator temperature
• CPC Class Codes: F25B 41/34 with the valve member being actuated by electric means, e.g. by piezoelectric actuators
• CPC Class Codes: F25B 49/022 Compressor control arrangements
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A microprocessor-based air conditioning/refrigeration control system adapted for use with a variable speed compressor measures acceleration of the compressor and the temperature or pressure of the refrigerant exiting therefrom, determines the rate of change of the temperature or pressure of the refrigerant, and decreases acceleration of the compressor if the rate of change of the temperature or pressure of the working fluid indicates surging of the compressor. Superheat of the refrigerant is maintained at a first predefined level while the compressor is operating at constant speed and is increased to a second, higher predefined level while the compressor is accelerating. The system is able to diagnose deterioration of the compressor by measuring and comparing power input to the compressor and rate of change of temperature or pressure of the refrigerant at the compressor between initial and subsequent periods, and differentiate between deterioration of a drive component or a pressurizing component of the compressor.

Claims

1. A method of controlling a refrigeration system having a working fluid and, in sequence, an evaporator, a variable speed centrifugal compressor, a condenser and an expansion valve, comprising:

a) accelerating rotation of said compressor;

b) measuring the acceleration of said compressor;

c) measuring the temperature or pressure of the working fluid at said compressor;

d) determining rate of change of the temperature or pressure of said working fluid during any acceleration of said compressor;

e) decreasing acceleration of said compressor if said rate of change of the temperature or pressure of said working fluid indicates surging of said compressor; and

f) repeating steps (b) through (e) until said compressor stops accelerating.

2. The method of claim 1 wherein said acceleration of said compressor in step (a) is to a predetermined maximum level.

3. The method of claim 1 wherein the temperature of the working fluid is measured in step (c) within or downstream adjacent to said compressor.

4. The method of claim 1 wherein the pressure of the working fluid is measured in step (c) within or downstream adjacent to said compressor.

5. Apparatus for controlling a refrigeration system having a working fluid and, in sequence, an evaporator, a variable speed centrifugal compressor, a condenser and an expansion valve, comprising:

a sensor for measuring the acceleration of said compressor;

a sensor for measuring the temperature or pressure of the working fluid at said compressor; and

a microprocessor control for determining rate of change of the temperature or pressure of said working fluid during any acceleration of said compressor and decreasing acceleration of said compressor if said rate of change of the temperature or pressure of said working fluid indicates surging of said compressor.

6. A method of controlling a refrigeration system having a working fluid and, in sequence, an evaporator, a variable speed centrifugal compressor, a condenser and an expansion valve, comprising:

a) during an initiation period, accelerating rotation of said compressor while;

i) measuring the acceleration of said compressor; and

ii) measuring rate of change of temperature or pressure of the working fluid at said compressor;

b) repeating step (a) to assemble a plurality of said measurements;

c) storing said acceleration and working fluid rate of change of temperature or pressure measurements during said initiation period;

d) subsequent to said initiation period, accelerating rotation of said compressor while;

i) measuring the acceleration of said compressor; and

ii) comparing said acceleration measurement during said subsequent period with said acceleration and working fluid rate of change of temperature or pressure measurements during said initiation period; and

e) decreasing acceleration of said compressor if, for a comparable acceleration during said initiation period, said rate of change of the temperature or pressure of said working fluid during said initiation period indicates surging of said compressor.

7. Apparatus for controlling a refrigeration system having a working fluid and, in sequence, an evaporator, a variable speed centrifugal compressor, a condenser and an expansion valve, comprising:

a sensor for measuring the acceleration of said compressor;

a sensor for measuring rate of change of temperature or pressure of the working fluid at said compressor; and

a microprocessor control for storing acceleration and working fluid rate of change of temperature or pressure measurements during an initiation period;

comparing an acceleration measurement during said subsequent period with said acceleration and working fluid rate of change of temperature or pressure measurements during said initiation period; and

decreasing acceleration of said compressor if, for a comparable acceleration during said initiation period, said rate of change of the temperature or pressure of said working fluid during said initiation period indicates surging of said compressor.