Compressor diagnostic and protection system and method

1. A system comprising:

a compressor operable in a refrigeration circuit and including a motor;

a current sensor providing a high-side signal indicative of an operating condition of a high-pressure side of the refrigeration circuit;

a discharge temperature sensor providing a low-side signal indicative of an operating condition of a low-pressure side of the refrigeration circuit; and

processing circuitry processing said high-side signal and said low-side signal to determine at least one of a non-measured condenser temperature and a non-measured evaporator temperature of the refrigeration circuit.

2. The system of claim 1 , wherein said processing circuitry determines at least one of a suction superheat and a discharge superheat.

3. The system of claim 1 , wherein said condenser temperature is a function of current.

4. The system of claim 1 , wherein said evaporator temperature is a function of said condenser temperature and discharge temperature.

5. The system of claim 2 , wherein said discharge superheat is a function of said condenser temperature and discharge temperature.

6. The system of claim 2 , wherein said suction superheat is a function of said discharge superheat.

7. The system of claim 2 , wherein said processing circuitry is operable to detect a floodback condition based on a comparison of discharge superheat temperature to a predetermined discharge superheat temperature.

8. The system of claim 7 , wherein said predetermined discharge superheat is approximately equal to forty degrees Fahrenheit or less.

9. The system of claim 1 , further comprising a system controller in communication with said processing circuitry.

10. The system of claim 9 , wherein said system controller receives said high-side signal and said low-side signal and is operable to verify at least one of said condenser temperature and said evaporator temperature determined by said processing circuitry.

11. The system of claim 9 , wherein said system controller includes at least one hand-held computer.

12. The system of claim 11 , wherein said hand-held computer is at least one of a personal data assistant and a cellular telephone.

13. The system of claim 2 , wherein said processing circuitry stores at least one of an equation and a constant for use in processing said high-side signal and said low-side signal.

14. The system of claim 2 , wherein said processing circuitry stores at least one of a relationship between compressor power and condenser temperature and between discharge temperature and evaporator temperature.

15. The system of claim 1 , wherein said processing circuitry references said high-side signal on a first relationship between compressor power and condenser temperature to determine said non-measured condenser temperature.

16. The system of claim 15 , wherein said processing circuitry references said non-measured condenser temperature on a second relationship between discharge temperature and evaporator temperature to determine said non-measured evaporator temperature.

17. The system of claim 15 , wherein said first relationship includes a plot of estimated evaporator temperature, said processing circuitry referencing said high-side signal on said first relationship to determine said non-measured condenser temperature based on said estimated evaporator temperature.

18. The system of claim 17 , wherein said plot of estimated evaporator temperature includes multiple plots of estimated evaporator temperatures.

19. The system of claim 15 , wherein said first relationship is a function defined by at least a compressor-specific constant, a compressor-specific coefficient of a variable condenser temperature, and a given approximate evaporator temperature.

20. The system of claim 19 , wherein said first relationship is:

P=C 0+( C 1* T cond )+( C 2* T evap )+( C 3* T cond ^2)+( C 4* T cond *T evap )+( C 5* T evap ^2)+( C 6* T cond ^3)+( C 7* T evap *T cond ^2)+( C 8* T cond *T evap ^2)+( C 9* T evap ^3),

where P is compressor power determined based on said high-side signal and a voltage supplied to said compressor, C 0 -C 9 are compressor-specific constants, T cond is said non-measured condenser temperature, and T evap is said given approximate evaporator temperature.

21. A method comprising:

generating a high-side signal indicative of high-pressure operating conditions at a compressor in a refrigeration circuit based on a current measurement of a current sensor;

generating a low-side signal indicative of low-pressure operating conditions at said compressor in said refrigeration circuit based on a temperature measurement of a discharge temperature sensor;

processing said high-side signal and said low-side signal;

calculating at least one of a non-measured condenser temperature and a non-measured evaporator temperature based on said high-side signal and said low-side signal; and

diagnosing said refrigeration circuit based on said at least one of said condenser temperature and said evaporator temperature.

22. The method of claim 21 , further comprising determining a discharge superheat and a suction superheat based on said high-side signal and said low-side signal to diagnose said refrigeration circuit.

23. The method of claim 22 , wherein said calculating includes referencing at least one of an equation and a constant loaded into processing circuitry of said refrigeration circuitry.

24. The method of claim 22 , wherein said calculating includes referencing at least one of a relationship between compressor power and condenser temperature and a relationship between discharge temperature and evaporator temperature.

25. The method of claim 22 , further comprising communicating at least one of said condenser temperature, said evaporator temperature, said discharge superheat, and said suction superheat to a system controller.

26. The method of claim 25 , further comprising verifying at least one of said condenser temperature, said evaporator temperature, said discharge superheat, and said suction superheat at said system controller.

27. The method of claim 26 , wherein said verifying includes calculating at least one of said condenser temperature, said evaporator temperature, said discharge superheat, and said suction superheat based on said high-side signal and said low-side signal communicated to said system controller by said processing circuitry.

28. The method of claim 26 , wherein said verifying includes calculating at least one of said condenser temperature, said evaporator temperature, said discharge superheat, and said suction superheat based on said high-side signal and said low-side signal detected by said system controller.

29. The method of claim 21 , further comprising calculating a condenser temperature difference including deriving an ambient temperature and subtracting said ambient temperature from said condenser temperature.

30. The method of claim 21 , wherein said calculating said non-measured condenser temperature includes referencing said high-side signal on a first relationship between compressor power and condenser temperature.

31. The method of claim 30 , wherein said calculating said non-measured evaporator temperature includes referencing said low-side signal and said calculated non-measured condenser temperature on a second relationship between discharge temperature and evaporator temperature.

32. The method of claim 30 , wherein said first relationship is a function defined by at least a compressor-specific constant, a compressor-specific coefficient of a variable condenser temperature, and a given approximate evaporator temperature.

33. The method of claim 32 , wherein said first relationship is:

P=C 0+( C 1* T cond )+( C 2* T evap )+( C 3* T cond ^2)+( C 4* T cond *T evap )+( C 5* T evap ^2)+( C 6* T cond ^3)+( C 7* T evap *T cond ^2)+( C 8* T cond *T evap ^2)+( C 9* T evap ^3),

where P is compressor power determined based on said high-side signal and a voltage applied to said compressor, C 0 -C 9 are compressor-specific constants, T cond is said non-measured condenser temperature, and T evap is said given approximate evaporator temperature.