Rotary compressors with variable speed and volume control

• US 10,533,556 B2
• Filed: 10/01/2014
• Issued: 01/14/2020
• Est. Priority Date: 10/01/2013
• Status: Active Grant

• Current Assignee: Trane International Inc. (Trane Technologies plc)
• Original Assignee: Trane International Inc. (Trane Technologies plc)
• Inventors: Johnson, Jay H., Sauls, John R., Powell, Gordon, Crum, Daniel R.
• Primary Examiner(s): Lettman, Bryan M
• Application Number:
  US14/504,182
• Publication Number:
  US 20150093273A1
• Time in Patent Office: 1,931 Days
• CPC Class Codes: F04C 18/16 with helical teeth, e.g. chevron-shaped, screw type for non-parallel axes of movement F04C18/48
• CPC Class Codes: F04C 2240/403 with inverter for speed control
• CPC Class Codes: F04C 2240/81 Sensor, e.g. electronic sensor for control or monitoring
• CPC Class Codes: F04C 2270/025 Controlled or regulated
• CPC Class Codes: F04C 2270/585 Controlled or regulated
• CPC Class Codes: F04C 28/08 characterised by varying the rotational speed
• CPC Class Codes: F04C 28/12 using sliding valves
• CPC Class Codes: F04C 28/14 using rotating valves
• 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 29/124 with inlet and outlet valves specially adapted for rotary or oscillating piston pumps
• CPC Class Codes: F25B 1/047 of screw type
• CPC Class Codes: F25B 2600/0253 with variable speed
• CPC Class Codes: F25B 49/022 Compressor control arrangements

Abstract

Systems and methods are used to control operation of a rotary compressor of a refrigeration system to improve efficiency by varying the volume ratio and the speed of the compressor in response to current operating and load conditions. The volume of the axial and/or radial discharge ports of the compressor can be varied to provide a volume ratio corresponding to operating conditions. In addition, permanent magnet motors and/or control of rotor tip speed can be employed for further efficiency gains.

Claims

1. A method for operating a refrigeration system, comprising:

receiving operational signals relating to operating pressures of the refrigeration system and a load on a rotary compressor of the refrigeration system;

adjusting a volume ratio of the rotary compressor in response to the operating pressures by controlling a volume of a discharge port of the rotary compressor, wherein the volume ratio is controlled by a valve that operates either at a first position or a second position corresponding to a closed and a fully open position, respectively;

changing a speed of a motor driving the rotary compressor in response to the volume ratio and the load on the rotary compressor while the valve is located in the closed position and while the valve is located in the fully open position; and

wherein an efficiency of the refrigeration system is optimized by coordinated control of both the valve and the speed of the motor.

2. The method of claim 1, wherein the motor is a permanent magnet motor.

3. The method of claim 1, wherein changing the speed includes controlling the speed of the motor with control signals from a variable frequency drive.

4. The method of claim 1, wherein adjusting the volume ratio of the rotary compressor further includes controlling a volume of a discharge port which comprises a radial discharge port and/or an axial discharge port of the rotary compressor.

5. The method of claim 1, wherein the speed of the motor operates at least one screw rotor of the rotary compressor at an optimum peripheral velocity that is independent of a peripheral velocity of the at least one screw rotor at a synchronous motor rotational speed for a rated capacity of the rotary compressor.

6. The method of claim 1, wherein adjusting the volume ratio of the rotary compressor includes moving the valve in a transverse direction, an axial direction or rotationally with respect to an axis of rotation of a compressor rotor.

7. The method of claim 1 further comprising operating the compressor in a steady state condition only when the valve is in the first position or the second position.

8. The method of claim 1 further comprising moving the valve from the first position to the second position when a saturated temperature of a condenser discharge flow drops and falls below a lower predetermined threshold temperature.

9. The method of claim 8, wherein the lower predetermined threshold temperature is between 90 and 120 degrees Fahrenheit.

10. The method of claim 1 further comprising moving the valve from the second position back to the first position when a saturated temperature of a condenser discharge flow increases and exceeds an upper predetermined threshold temperature.