Screw compressor drive control

Patent metadata

Field	Value
Publication number	US-10352608-B2
Application number	US-201715676220-A
Country	US
Kind code	B2
Filing date	Aug 14, 2017
Priority date	Aug 20, 2009
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

An embodiment of method used to control operation of a screw compressor of a refrigeration system may include receiving status signals regarding operation of the screw compressor of the refrigeration system. The method may further include determining an operating point of the screw compressor based upon the received status signals, and selecting a torque profile for the screw compressor based upon the operating point. The method may also include driving the screw compressor per the selected torque profile. Refrigeration systems and compressor systems suitable for implementing the method are also presented.

First claim

What is claimed is:

1. A compressor system, comprising
a screw compressor comprising a suction port to receive fluid at a suction pressure, a plurality of meshing screw rotors to compress the fluid, and a discharge port to discharge the compressed fluid at a discharge pressure that is higher than the suction pressure;
an electric motor to receive control signals and to drive the plurality of meshing screw rotors at a speed per the received control signals;
a controller to receive status signals indicative of an operating point of the screw compressor, to select a torque profile for the screw compressor based upon the operating point of the screw compressor, and to generate command signals that request the electric motor be driven per the selected torque profile; and
a variable frequency drive to receive the command signals and to generate the control signals that drive the electric motor per the selected torque profile.

2. The compressor system of claim 1 , further comprising a memory comprising a plurality of torque profiles, wherein the controller is to select the torque profile from the plurality of torque profiles based upon the operating point indicated by the status signals.

3. The compressor system of claim 1 , further comprising a memory comprising a plurality of torque profiles, wherein the controller is to identify the operating point of the screw compressor based upon the status signals, and is to select the torque profile from the plurality of torque profiles based upon the identified operating point.

4. The compressor system of claim 1 , further comprising a memory comprising a plurality of torque profiles, wherein in response to the status signals indicating the screw compressor has achieved a stable operating point, the controller is to select a torque profile for the screw compressor based upon the plurality of torque profiles and the stable operating point indicated by the status signals.

5. The compressor system of claim 1 , further comprising a memory comprising a starting torque profile, an acceleration torque profile, a deceleration torque profile, a default torque profile, and a plurality of operating torque profiles, wherein the controller is to select the torque profile from the starting torque profile, the acceleration torque profile, the deceleration torque profile, the default torque profile, and the plurality of operating point torque profiles based upon the status signals.

6. The compressor system of claim 1 , wherein
the control signals comprise polyphase alternating current control signals,
the electric motor comprises a permanent magnet motor to drive the screw compressor at a drive speed controlled by the polyphase alternating current control signals, and
the variable frequency drive adjusts a frequency of the polyphase alternating current control signals to adjust the drive speed of the permanent magnet motor per the command signals of the controller and the selected torque profile.

7. The compressor system of claim 1 , further comprising
a suction port sensor proximate the suction port of the screw compressor to provide the status signals with suction port measurements of fluid entering the suction port of the screw compressor,
a discharge port sensor proximate the discharge port of the screw compressor to provide the status signals with discharge port measurements of fluid discharged from the discharge port of the screw compressor, and
a torque sensor to provide the status signals with torque measurements of torque applied by the electric motor to the screw compressor,
wherein the controller is to determine the operating point of the screw compressor based upon at least the suction port measurements, the discharge port measurements, and the torque measurements of the status signals.

8. The compressor system of claim 1 , further comprising
a suction port sensor proximate the suction port of the screw compressor to provide the status signals with suction port measurements of fluid entering the suction port of the screw compressor,
a discharge port sensor proximate the discharge port of the screw compressor to provide the status signals with discharge port measurements of fluid discharged from the discharge port of the screw compressor, and
one or more electrical sensors positioned proximate the electric motor to sense electrical operating characteristics of the electric motor and to provide status signals indicative of the sensed electrical operating characteristics,
wherein the controller is to determine the operating point of the screw compressor based upon at least the suction port measurements, the discharge port measurements, and the electric current measurements.

9. A method to control operation of a screw compressor of a refrigeration system, comprising
receiving status signals regarding operation of the screw compressor of the refrigeration system;
determining an operating point of the screw compressor based upon the received status signals;
selecting a torque profile for the screw compressor based upon the operating point; and
driving the screw compressor per the selected torque profile.

10. The method of claim 9 , further comprising
selecting a starting torque profile for the screw compressor in response to determining that the screw compressor is in a start mode; and
driving the screw compressor per the starting torque profile.

11. The method of claim 9 , further comprising
selecting an acceleration torque profile for the screw compressor in response to a increasing speed of the screw compressor; and
driving the screw compressor per the selected acceleration torque profile.

12. The method of claim 9 , further comprising
selecting a deceleration torque profile for the screw compressor in response to a decreasing speed of the screw compressor; and
driving the screw compressor per the selected deceleration torque profile.

13. The method of claim 9 , further comprising
selecting a default torque profile in response to determining based upon the status signal that the screw compressor is not currently operating at a steady operating point, and
driving the screw compressor per the selected default torque profile.

14. The method of claim 9 , further comprising selecting the torque profile in response to determining based upon the status signals that the screw compressor is currently operating at a stable operating point.

15. The method of claim 9 , further comprising selecting the torque profile in response to measurements provided by the status signals achieving a predetermined level of stability.

16. A refrigeration system, comprising
a screw compressor comprising a suction port to receive fluid at a suction pressure, a plurality of meshing screw rotors to compress the fluid, and a discharge port to discharge the compressed fluid at a discharge pressure that is higher than the suction pressure;
a condenser coupled to the discharge port of the screw compressor, the condenser to cool and condense fluid received from the discharge port;
an expansion valve coupled to the condenser, the expansion valve to evaporate at least a portion of fluid received from the condenser by lowering pressure of fluid received from the condenser;
an evaporator coupled to the expansion valve, the evaporator to evaporate fluid received from the expansion valve and to provide fluid to the suction port of the screw compressor;
an electric motor system to receive command signals and to drive the plurality of meshing screw rotors per the received command signals; and
a controller to receive status signals indicative of an operating point of the

Assignees

• Trane Int Inc

Inventors

• Foye David M
• West Nathan T
• Beekman Dennis M
• Sauls John R

Classifications

• F25B2600/0253

  with variable speed · CPC title

• F04C28/08

  characterised by varying the rotational speed · CPC title

• F04C2270/03

  Torque · CPC title

• F25B1/047

  of screw type · CPC title

• F25B49/025

  Motor control arrangements · CPC title