Compressor protection and grid fault detection device

• US 10,418,800 B2
• Filed: 04/09/2018
• Issued: 09/17/2019
• Est. Priority Date: 02/20/2008
• Status: Active Grant

• Current Assignee: Copeland Corporation LLC (Emerson Electric Company)
• Original Assignee: Emerson Climate Technologies Incorporated (Emerson Electric Company)
• Inventors: Jayanth, Nagaraj, Ramayya, George
• Primary Examiner(s): Glass, Erick D
• Application Number:
  US15/948,864
• Publication Number:
  US 20180233900A1
• Time in Patent Office: 526 Days
• Field of Search: 318802
• CPC Class Codes: F25B 2500/19 Calculation of parameters
• CPC Class Codes: F25B 2600/0251 with on-off operation
• CPC Class Codes: F25B 2700/13 Mass flow of refrigerants
• CPC Class Codes: F25B 2700/151 of the compressor motor
• CPC Class Codes: F25B 2700/2115 of a compressor or the drive means therefor
• CPC Class Codes: F25B 49/022 Compressor control arrangements
• CPC Class Codes: G01R 19/10 Measuring sum, difference or ratio
• CPC Class Codes: G01R 19/16538 in AC or DC supplies G01R19/16519 and G01R19/16528 take precedence
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: H02H 7/08 for dynamo-electric motors
• CPC Class Codes: H02H 7/09 against over-voltage; against reduction of voltage; against phase interruption
• CPC Class Codes: H02H 7/20 for electronic equipment for converters H02H7/10; for electric measuring instruments G01R1/36; for dc voltage or current semiconductor regulators G05F1/569; for amplifiers H03F1/52; for electronic switching circuits H03K17/08
• CPC Class Codes: H02P 29/0241 the fault being an overvoltage

Abstract

A method for monitoring a compressor includes measuring a power factor of a motor of a compressor. The method includes selectively detecting an occurrence of a fault event of an electrical grid based on the power factor. The method includes, in response to detecting that the fault event has occurred, switching the compressor from a first state to a second state. The compressor consumes less power in the second state than in the first state. The method includes identifying an apparent conclusion of the fault event. The method includes, in response to the apparent conclusion of the fault event, waiting for a first delay period before switching the motor of the compressor back to the first state.

Claims

1. A method for monitoring a compressor that is powered by an electrical grid, the method comprising:

measuring a power factor of a motor of the compressor;

selectively detecting an occurrence of a fault event of the electrical grid based on the power factor;

in response to detecting that the fault event has occurred, switching the compressor from a first state to a second state, wherein the compressor consumes less power in the second state than in the first state;

identifying an apparent conclusion of the fault event; and

in response to the apparent conclusion of the fault event, waiting for a first delay period before switching the compressor back to the first state.

2. The method of claim 1 wherein:

the first state of the compressor corresponds to an ON state of the motor; and

the second state of the compressor corresponds to an OFF state of the motor.

3. The method of claim 1 further comprising:

measuring (i) a first set of power factor values over a first period of time and (ii) a second set of power factor values over a second period of time subsequent to the first period of time;

calculating (i) a first average for the first set of power factor values and (ii) a second average for the second set of power factor values;

calculating a ratio of the second average divided by the first average; and

in response to the ratio being less than a predetermined ratio, detecting that the fault event has occurred.

4. The method of claim 1 further comprising choosing the first delay period according to a randomized process.

5. The method of claim 1 further comprising:

maintaining a count of occurrences of the fault event; and

deactivating the motor of the compressor in response to the count being greater than a first threshold.

6. The method of claim 5 wherein deactivating the motor of the compressor prevents the motor of the compressor from being switched back to the first state until a service event occurs.

7. The method of claim 5 further comprising resetting the count in response to a time period that the motor of the compressor has been running exceeding a second threshold.

8. The method of claim 1 wherein measuring the power factor comprises:

measuring a current drawn by the motor of the compressor;

measuring a voltage of the electric grid; and

calculating the power factor from the measured current and the measured voltage.

9. The method of claim 1 wherein:

identifying the apparent conclusion of the fault event includes comparing a measured voltage of the electric grid to a voltage threshold; and

in response to the measured voltage being greater than the voltage threshold for a predetermined period of time, the apparent conclusion of the fault event is identified.

10. The method of claim 1 wherein measurement of the power factor is delayed until a predetermined period has passed following startup of the motor of the compressor.

11. A compressor monitoring system comprising:

a power factor monitor module configured to measure a power factor of a motor of a compressor; and

a control module configured to;

selectively detect an occurrence of a fault event of an electrical grid based on the power factor;

in response to detecting that the fault event has occurred, switch the compressor from a first state to a second state;

identify an apparent conclusion of the fault event; and

in response to the apparent conclusion of the fault event, wait for a first delay period before switching the compressor back to the first state.

12. The compressor monitoring system of claim 11 wherein:

the first state of the compressor corresponds to an ON state of the motor; and

the second state of the compressor corresponds to an OFF state of the motor.

13. The compressor monitoring system of claim 11 further comprising an averaging module configured to:

measure (i) a first set of power factor values over a first period of time and (ii) a second set of power factor values over a second period of time subsequent to the first period of time;

calculate (i) a first average for the first set of power factor values and (ii) a second average for the second set of power factor values; and

calculate a ratio of the second average divided by the first average.

14. The compressor monitoring system of claim 11 wherein the control module is configured to choose the first delay period according to a randomized process.

15. The compressor monitoring system of claim 11 wherein the control module is configured to:

maintain a count of occurrences of the fault event; and

deactivate the motor of the compressor in response to the count being greater than a first threshold.

16. The compressor monitoring system of claim 15 wherein deactivating the motor of the compressor includes preventing the motor of the compressor from being switched back to the first state until a service event occurs.

17. The compressor monitoring system of claim 15 wherein the control module is configured to reset the count in response to a time period that the motor of the compressor has been running being exceeding a second threshold.

18. The compressor monitoring system of claim 11 wherein the measured power factor is calculated from a measured current drawn by the motor of the compressor and a measured voltage of power received by the motor of the compressor.

19. The compressor monitoring system of claim 11 wherein:

the control module identifies the apparent conclusion of the fault event by comparing a measured voltage to a voltage threshold, and

in response to the measured voltage being greater than the voltage threshold for a predetermined period of time, the apparent conclusion of the fault event is identified.

20. The compressor monitoring system of claim 11 wherein measurement of the power factor is delayed until a predetermined period has passed following startup of the motor of the compressor.