Controls and operation of variable frequency drives

• US 10,746,448 B2
• Filed: 04/24/2017
• Issued: 08/18/2020
• Est. Priority Date: 03/11/2013
• Status: Active Grant

• Current Assignee: Trane International Inc. (Trane Technologies plc)
• Original Assignee: Trane International Inc. (Trane Technologies plc)
• Inventors: Sykora, Benjamin James, West, Nathan Thomas, Foye, David Marshall, Beekman, Dennis Myron, Anderson, Korwin Jay, Bakkestuen, Robert
• Primary Examiner(s): Landrum, Edward F
• Assistant Examiner(s): Cox, Alexis K
• Application Number:
  US15/495,269
• Publication Number:
  US 20170227273A1
• Time in Patent Office: 1,212 Days
• CPC Class Codes: F04C 18/02 of arcuate-engagement type, i.e. with circular translatory movement of co-operating members, each member having the same number of teeth or tooth-equivalents
• CPC Class Codes: F04C 18/0215 where only one member is moving
• 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 2240/40 Electric motor
• CPC Class Codes: F04C 2240/403 with inverter for speed control
• CPC Class Codes: F04C 2240/808 Electronic circuits (e.g. inverters) installed inside the machine
• CPC Class Codes: F04C 2270/02 Power
• CPC Class Codes: F04C 2270/80 Diagnostics
• CPC Class Codes: F04C 2270/86 Detection
• CPC Class Codes: F04C 28/04 specially adapted for reversible pumps
• CPC Class Codes: F04C 28/08 characterised by varying the rotational speed
• CPC Class Codes: F04C 28/28 Safety arrangements; Monitoring
• CPC Class Codes: F04C 29/0085 Prime movers
• CPC Class Codes: F25B 1/00 Compression machines, plants or systems with non-reversible cycle F25B3/00, F25B5/00, F25B6/00, F25B7/00, F25B9/00 take precedence
• CPC Class Codes: F25B 2339/047 Water-cooled condensers
• 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 2600/0253 with variable speed
• CPC Class Codes: F25B 2700/151 of the compressor motor
• CPC Class Codes: F25B 2700/171 of the compressor
• CPC Class Codes: F25B 31/02 : of motor-compressor units
• CPC Class Codes: F25B 49/022 : Compressor control arrangements
• CPC Class Codes: F25B 49/025 : Motor control arrangements
• CPC Class Codes: G05D 23/00 : Control of temperature
• CPC Class Codes: Y02B 30/70 : Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A system includes a refrigerant compressor, an electric motor and configured to drive the refrigerant compressor, and a controller. The controller is configured to operate the compressor in a liquid clearing start mode where electrical current through the motor is prevented from exceeding a predetermined current limit for a period of time not to exceed a predetermined period of time, and is configured to operate the compressor in a run mode in response to determining the motor exceeds a predetermined speed threshold at or before expiration of the predetermined period of time, wherein the run mode does not prevent electrical current through the motor from exceeding said predetermined current limit.

Claims

1. A system, comprising:

a refrigerant compressor;

an electric motor configured to drive the refrigerant compressor;

a controller configured to operate the compressor to clear liquid from the compressor by controlling the motor to operate in a liquid clearing mode where electrical current through the motor is prevented from exceeding a predetermined current limit for a period of time not to exceed a predetermined period of time, and to operate the compressor in a run mode in response to determining the motor exceeds a predetermined speed threshold at or before expiration of the predetermined period of time, wherein while the motor is controlled by the controller in the run mode the motor does not prevent electrical current through the motor from exceeding said predetermined current limit; and

a sensor configured to provide an input to the controller wherein the controller is configured to determine motor speed in response to the input.

2. The system of claim 1, wherein the controller is further configured to stop operation of the compressor in response to determining the motor fails to reach the predetermined speed threshold at or before expiration of the predetermined period of time.

3. The system of claim 1, wherein operation of the compressor in the run mode includes increased motor speed relative to operation of the compressor in the liquid clearing mode.

4. The system of claim 1, wherein the controller is further configured to operate the compressor in the liquid clearing mode in response to the compressor being started and a determination that motor torque exceeds a predetermined value.

5. The system of claim 1, wherein the sensor is configured to measure motor current and provide a corresponding indication to the controller, wherein the controller is further configured to use the measured motor current to determine motor torque.

6. The system of claim 1, wherein the controller is further configured to automatically operate the compressor in the liquid clearing mode each time the compressor is started.

7. The system of claim 1, wherein the predetermined current limit corresponds to a maximum current rating for operation of the compressor with the speed of the motor at or under the speed of the predetermined speed threshold in order to avoid compressor damage.

8. The system of claim 1, further comprising a variable frequency drive, a condenser and an evaporator.

9. A method, comprising:

providing a system including a refrigerant compressor, an electric motor configured to drive the refrigerant compressor, a controller configured to operate the compressor to clear liquid from the compressor by controlling the motor to operate in a liquid clearing mode where electrical current through the motor is prevented from exceeding a predetermined current limit for a period of time not to exceed a predetermined period of time, and to operate the compressor in a run mode in response to determining the motor exceeds a predetermined speed threshold at or before expiration of the predetermined period of time, and a sensor configured to provide an input to the controller, wherein the controller is configured to determine motor speed in response to the input, and wherein while the motor is controlled by the controller in the run mode the motor does not prevent electrical current through the motor from exceeding said predetermined current limit;

operating the controller to operate the compressor in the liquid clearing mode where electrical current through the motor is prevented from exceeding a predetermined current limit for a predetermined period of time; and

operating the controller to operate the compressor in a run mode in response to determining the motor exceeds a predetermined speed threshold at or before expiration of the predetermined period of time, wherein in the run mode the motor does not prevent electrical current through the motor from exceeding the predetermined current limit.

10. The method of claim 9, comprising operating the controller to stop operation of the compressor in response to determining the motor fails to reach the predetermined speed threshold at or before expiration of the predetermined period of time.

11. The method of claim 9, wherein the operating the controller to operate the compressor in a run mode includes increased motor speed relative to operation of the compressor in the liquid clearing mode.

12. The method of claim 9, wherein the operating the controller to operate the compressor in the liquid clearing mode is performed in response to the compressor being started and a determination that motor torque exceeds a predetermined value.

13. The method of claim 9, wherein the operating the controller to operate the compressor in the liquid clearing mode is performed each time the compressor is started.

14. The method of claim 9, wherein the predetermined current limit corresponds to a maximum current rating for operation of the compressor with the speed of the motor at or under the speed of the predetermined speed threshold in order to avoid compressor damage.

15. The method of claim 9, wherein operating the controller to operate the compressor in the liquid clearing mode is effective to clear liquid from the compressor.