초록 ▼

A method for controlling at least one electronic expansion valve coupled to an economizer in a refrigeration system in order to dynamically control the refrigeration system operating conditions and in order to accommodate more than one set of operating conditions. The system can also be used to cont

A method for controlling at least one electronic expansion valve coupled to an economizer in a refrigeration system in order to dynamically control the refrigeration system operating conditions and in order to accommodate more than one set of operating conditions. The system can also be used to control the capacity of the system. More specifically, the method can include determining the required capacity of the system and adjusting the flow of refrigerant through the electronic expansion valve to adjust the actual capacity of the system toward the required capacity of the system. In another aspect of the invention, the system is operated to maintain the power of the system below a threshold value (e.g., below a max rated horsepower). This method includes determining the power required to operate the compressor based on the measurement of system parameters; comparing the power required to a threshold value; and adjusting the flow of refrigerant through the electronic expansion valve in order to keep the power required below the threshold value. In yet another aspect of the invention, the system is operated in order to prevent overheating of the compressor. More specifically, the flow of refrigerant from the heat exchanger to the compressor can be adjusted so that some amount of liquid refrigerant is provided to quench the compressor.

대표청구항 ▼

A method for controlling at least one electronic expansion valve coupled to an economizer in a refrigeration system in order to dynamically control the refrigeration system operating conditions and in order to accommodate more than one set of operating conditions. The system can also be used to cont

A method for controlling at least one electronic expansion valve coupled to an economizer in a refrigeration system in order to dynamically control the refrigeration system operating conditions and in order to accommodate more than one set of operating conditions. The system can also be used to control the capacity of the system. More specifically, the method can include determining the required capacity of the system and adjusting the flow of refrigerant through the electronic expansion valve to adjust the actual capacity of the system toward the required capacity of the system. In another aspect of the invention, the system is operated to maintain the power of the system below a threshold value (e.g., below a max rated horsepower). This method includes determining the power required to operate the compressor based on the measurement of system parameters; comparing the power required to a threshold value; and adjusting the flow of refrigerant through the electronic expansion valve in order to keep the power required below the threshold value. In yet another aspect of the invention, the system is operated in order to prevent overheating of the compressor. More specifically, the flow of refrigerant from the heat exchanger to the compressor can be adjusted so that some amount of liquid refrigerant is provided to quench the compressor. d in the hydraulic system comprises activating the valve based on the equivalent flow coefficient. 4. The method as recited in claim 1 wherein controlling the fluid in the hydraulic system comprises: calculating a pressure setpoint based on the equivalent flow coefficient; and controlling pressure in at least one of the supply line and the return line in response to the pressure setpoint. 5. The method as recited in claim 4 further comprising: sensing pressure in the return line to produce a return pressure measurement; wherein calculating a pressure setpoint also is based on the return pressure measurement; and wherein controlling the pressure controls pressure in the supply line. 6. The method as recited in claim 4 further comprising: sensing a pressure produced by the force acting on the hydraulic actuator to produce an actuator pressure measurement; and wherein calculating a pressure setpoint also is based on the actuator pressure measurement. 7. The method as recited in claim 1 wherein controlling the fluid in the hydraulic system comprises using the parameter to control pressure in at least one of the supply line and the return line in response to the force acting on the hydraulic actuator. 8. A method of operating a hydraulic system in which a hydraulic actuator is connected in a circuit branch between a supply line containing pressurized fluid and a return line connected to a tank, said method comprising: sensing pressure in the supply line to produce a supply pressure measurement; sensing pressure in the return line to produce a return pressure measurement; sensing a parameter which varies with changes of a force acting on the hydraulic actuator; deriving an equivalent flow coefficient which characterizes fluid flow through the hydraulic circuit and which is derived from the supply pressure measurement, the return pressure measurement, and the parameter; and controlling the fluid in the hydraulic system based on the equivalent flow coefficient. 9. The method as recited in claim 8 wherein determining the parameter comprises sensing a pressure produced by the force acting on the hydraulic actuator. 10. The method as recited in claim 8 wherein the hydraulic actuator has a first port and a second port, and sensing a parameter comprises: sensing pressure at the first port to produce a first port pressure measurement; and sensing pressure at the second port to produce a second port pressure measurement. 11. The method as recited in claim 8 further comprises producing a requested velocity for the hydraulic actuator, and wherein equivalent flow coefficient also is based on the requested velocity. 12. In a hydraulic system having a circuit branch in which a first electrohydraulic proportional valve couples a first port of a hydraulic actuator to a supply line containing pressurized fluid and a second electrohydraulic proportional valve couples a second port of the hydraulic actuator to a return line connected to a tank, a method comprising: sensing pressure in the supply line; sensing pressure in the return line; sensing pressure at the first port; sensing pressure at the second port; deriving an equivalent flow coefficient, Keq, representing fluid conduction of the hydraulic circuit branch, wherein that deriving is based on the pressure in the supply line, the pressure in the return line, the pressure at the first port, and the pressure at the second port; and controlling operation of the circuit branch based on the equivalent flow coefficient. 13. The method as recited in claim 12 wherein controlling operation of the circuit branch comprises activating the first electrohydraulic proportional valve and the second electrohydraulic proportional valve based on the equivalent flow coefficient. 14. The method as recited in claim 12 wherein the hydraulic actuator comprises a cylinder and a piston which defines first and second chambers in the cylinder, wherein the piston has a first surfa