Variable speed compressor protection system and method

• US 9,494,158 B2
• Filed: 05/14/2013
• Issued: 11/15/2016
• Est. Priority Date: 10/08/2007
• Status: Active Grant

• Current Assignee: Copeland Corporation LLC (Emerson Electric Company)
• Original Assignee: Emerson Climate Technologies Incorporated (Emerson Electric Company)
• Inventors: Pham, Hung M., Seibel, Stephen M.
• Primary Examiner(s): FLANIGAN, ALLEN J
• Application Number:
  US13/893,493
• Publication Number:
  US 20130240043A1
• Time in Patent Office: 1,281 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: F04B 2203/0204 Frequency of the electric current
• CPC Class Codes: F04B 2203/0209 Rotational speed
• CPC Class Codes: F04B 39/06 Cooling; Heating; Prevention of freezing
• CPC Class Codes: F04B 39/12 Casings; Cylinders; Cylinder heads; Fluid connections
• CPC Class Codes: F04B 39/123 Fluid connections
• CPC Class Codes: F04B 49/06 Control using electricity regulating by means of floats actuating electric switches F04B49/04
• CPC Class Codes: F04C 18/0215 where only one member is moving
• CPC Class Codes: F04C 2210/227 Steam
• CPC Class Codes: F04C 2210/26 Refrigerants with particular properties, e.g. HFC-134a
• CPC Class Codes: F04C 2240/403 with inverter for speed control
• CPC Class Codes: F04C 2240/803 Electric connectors or cables; Fittings therefor
• CPC Class Codes: F04C 2240/81 Sensor, e.g. electronic sensor for control or monitoring
• CPC Class Codes: F04C 2270/19 Temperature
• CPC Class Codes: F04C 2270/80 Diagnostics
• CPC Class Codes: F04C 23/008 Hermetic pumps
• CPC Class Codes: F04C 28/08 characterised by varying the rotational speed
• CPC Class Codes: F04C 28/24 characterised by using valves controlling pressure or flow rate, e.g. discharge valves or unloading valvesF04C28/10 takes precedence
• CPC Class Codes: F04C 28/28 Safety arrangements; Monitoring
• CPC Class Codes: F04C 29/0085 Prime movers
• CPC Class Codes: F25B 2500/08 Exceeding a certain temperature value in a refrigeration component or cycle
• CPC Class Codes: F25B 2500/19 : Calculation of parameters
• CPC Class Codes: F25B 2500/28 : Means for preventing liquid refrigerant entering into the compressor
• CPC Class Codes: F25B 2600/021 : Inverters therefor
• CPC Class Codes: F25B 2600/025 : by controlling speed
• CPC Class Codes: F25B 2600/2513 : Expansion valves
• CPC Class Codes: F25B 2700/151 : of the compressor motor
• CPC Class Codes: F25B 2700/1931 : Discharge pressures
• CPC Class Codes: F25B 2700/21 : Temperatures
• CPC Class Codes: F25B 2700/21151 : at the suction side of the compressor
• CPC Class Codes: F25B 2700/21152 : at the discharge side of the compressor
• CPC Class Codes: F25B 2700/21163 : of the refrigerant at the outlet of the condenser
• CPC Class Codes: F25B 2700/21174 : of the refrigerant at the inlet of the evaporator
• CPC Class Codes: F25B 31/006 : Cooling of compressor or motor
• 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: Y02B 30/70 : Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
• CPC Class Codes: Y10T 137/0318 : Processes
• CPC Class Codes: Y10T 137/85986 : Pumped fluid control

Abstract

A system and method for a compressor includes a compressor connected to a condenser, a discharge line temperature sensor that outputs a discharge line temperature signal corresponding to a discharge line temperature of refrigerant leaving the compressor, and a control module connected to the discharge line temperature sensor. The control module determines a saturated condenser temperature, calculates a discharge superheat temperature based on the saturated condenser temperature and the discharge line temperature, and monitors a flood back condition of the compressor by comparing the discharge superheat temperature with a predetermined threshold. The control module increases a speed of the compressor or decreases an opening of an expansion valve associated with the compressor when the discharge superheat temperature is less than or equal to the predetermined threshold.

Claims

1. A system comprising:

a compressor connected to a condenser;

a discharge line temperature sensor that outputs a discharge line temperature signal corresponding to a discharge line temperature of refrigerant leaving the compressor;

a control module connected to the discharge line temperature sensor, said control module receiving compressor power data, determining a saturated condenser temperature as a function of the compressor power data and a speed of the compressor, calculating a discharge superheat temperature based on the saturated condenser temperature and the discharge line temperature, monitoring a flood back condition of the compressor by comparing the discharge superheat temperature with a predetermined threshold, and, when the discharge superheat temperature is less than or equal to the predetermined threshold, increasing the speed of the compressor or decreasing an opening of an expansion valve associated with the compressor.

2. The system of claim 1 wherein the predetermined threshold is thirty degrees Fahrenheit.

3. The system of claim 1 wherein the control module increases the speed of the compressor when the discharge superheat temperature is less than or equal to the predetermined threshold.

4. The system of claim 1 wherein the control module decreases the opening of the expansion valve when the discharge superheat temperature is less than or equal to the predetermined threshold.

5. The system of claim 1 wherein the control module monitors a sudden flood back condition by determining whether the discharge superheat temperature decreases by a predetermined amount within a predetermined time period.

6. The system of claim 1 wherein the control module receives a discharge pressure signal corresponding to a discharge pressure of refrigerant leaving the compressor and determines the saturated condenser temperature based on the discharge pressure.

7. The system of claim 1 further comprising an evaporator connected to the compressor and the condenser, wherein the control module receives compressor power data, determines a saturated evaporator temperature as a function of the saturated condenser temperature, the discharge line temperature, and the speed of the compressor, and determines the saturated condenser temperature as a function of the compressor power data, the speed of the compressor, and the saturated evaporator temperature.

8. The system of claim 7 wherein the control module performs multiple iterations of determining the saturated condenser temperature and the saturated evaporator temperature to achieve convergence.

9. The system of claim 1 wherein the control module receives compressor power data and determines the saturated condenser temperature as a function of the compressor power data, the speed of the compressor, and the discharge line temperature.

10. A method comprising:

receiving, with a control module, compressor power data of a compressor;

determining, with the control module, a saturated condenser temperature of a condenser connected to the compressor as a function of the compressor power data and a speed of the compressor;

receiving, with the control module, a discharge line temperature signal that corresponds to a discharge line temperature of refrigerant leaving the compressor;

calculating, with the control module, a discharge superheat temperature based on the saturated condenser temperature and the discharge line temperature;

monitoring, with the control module, a flood back condition of the compressor by comparing the discharge superheat temperature with a predetermined threshold; and

increasing the speed of the compressor or decreasing an opening of an expansion valve, with the control module, when the discharge superheat temperature is less than or equal to the predetermined threshold.

11. The method of claim 10 wherein the predetermined threshold is thirty degrees Fahrenheit.

12. The method of claim 10 wherein the control module increases the speed of the compressor when the discharge superheat temperature is less than or equal to the predetermined threshold.

13. The method of claim 10 wherein the control module decreases the opening of the expansion valve when the discharge superheat temperature is less than or equal to the predetermined threshold.

14. The method of claim 10 further comprising monitoring, with the control module, a sudden flood back condition by determining whether the discharge superheat temperature decreases by a predetermined amount within a predetermined time period.

15. The method of claim 10 further comprising receiving, with the control module, a discharge pressure signal corresponding to a discharge pressure of refrigerant leaving the compressor and determining the saturated condenser temperature based on the discharge pressure.

16. The method of claim 10 further comprising receiving, with the control module, compressor power data, determining a saturated evaporator temperature of an evaporator connected to the compressor and the condenser as a function of the saturated condenser temperature, the discharge line temperature, and the speed of the compressor, and determining the saturated condenser temperature as a function of the compressor power data, the speed of the compressor, and the saturated evaporator temperature.

17. The method of claim 16 further comprising performing, with the control module, multiple iterations of determining the saturated condenser temperature and the saturated evaporator temperature to achieve convergence.

18. The method of claim 10 further comprising receiving, with the control module, compressor power data and determining the saturated condenser temperature as a function of the compressor power data, the speed of the compressor, and the discharge line temperature.