SYSTEMS AND METHODS FOR PROTECTING THREE-PHASE MOTORS

• US 20130120881A1
• Filed: 01/10/2013
• Published: 05/16/2013
• Est. Priority Date: 09/27/2010
• Status: Active Grant

• Current Assignee: Copeland Corporation LLC (Emerson Electric Company)
• Original Assignee: Emerson Climate Technologies Incorporated (Emerson Electric Company)
• Inventors: Jayanth, Nagaraj B., Warner, Wayne R.
• Granted Patent: US 8,604,737 B2
• Time in Patent Office: Days
• US Class Current: 361/24
• CPC Class Codes: F25B 2700/151 of the compressor motor
• CPC Class Codes: F25B 2700/2106 of fresh outdoor air
• CPC Class Codes: F25B 2700/21156 of the motor
• CPC Class Codes: F25B 49/005 of safety devices F25B49/02 and F25B49/04 take precedence
• CPC Class Codes: F25D 29/006 Safety devices
• CPC Class Codes: H02H 3/08 responsive to excess current responsive to abnormal temperature caused by excess current H02H5/04
• CPC Class Codes: H02H 5/041 additionally responsive to excess current H02H5/048 takes precedence
• CPC Class Codes: H02H 7/0833 for electric motors with control arrangements
• CPC Class Codes: H02H 7/0852 directly responsive to abnormal temperature by using a temperature sensor in a control circuit H02H7/0833

Abstract

A three-phase electric motor of a compressor receives first, second, and third phases from a three-phase power supply. A method for protecting the motor includes, using a line break protector, disconnecting the motor from only the first phase in response to a temperature being greater than a predetermined temperature threshold. The method also includes measuring a first current flowing through the line break protector, and determining a current value based on the first current independent of current in the second and third phases. The method further includes disconnecting the motor from the first, second, and third phases in response to the current value being less than or equal to a predetermined threshold.

Claims

1. A system for protecting a three-phase electric motor of a compressor, the motor receiving first, second, and third phases from a three-phase power supply, the system comprising:

a single-phase line break protector that disconnects the motor from only the first phase in response to a temperature being greater than a predetermined temperature threshold;

a first current sensor that measures a first current flowing through the single-phase line break protector; and

a control module that (i) determines a current value based on the first current independent of current in the second and third phases, and (ii) disconnects the motor from the first, second, and third phases in response to the current value being less than or equal to a predetermined threshold.

2. The system of claim 1 wherein the control module disconnects the motor from the first, second, and third phases by actuating a three-phase interruption device that electrically disconnects the first, second, and third phases from the motor.

3. The system of claim 2 further comprising the three-phase interruption device, wherein the three-phase interruption device includes a contactor.

4. The system of claim 1 wherein the predetermined threshold is zero.

5. The system of claim 1 wherein the current value includes at least one of (i) a peak of the first current during a predetermined period and (ii) a root mean squared (RMS) of the first current during the predetermined period.

6. The system of claim 1 further comprising:

a second current sensor that measures a second current corresponding to one of the second and third phases,

wherein the control module selectively detects at least one of a phase loss and a reversed phase sequence based on the first current and the second current, and

wherein the control module disconnects the motor from the first, second, and third phases in response to one or more of the phase loss and the reversed phase sequence being detected.

7. The system of claim 1 wherein the single-phase line break protector is located proximate to a winding of the motor, and wherein the temperature is responsive to heat generated by the winding during operation of the motor.

8. The system of claim 1 wherein the control module reconnects the motor to the first, second, and third phases in response to a predetermined shutdown period passing subsequent to disconnecting the first, second, and third phases from the motor.

9. The system of claim 1 wherein:

the single-phase line break protector includes first and second elements that selectively conduct the first current,

at least one of the first and second elements bends based on the temperature, and

the temperature is responsive to a magnitude of the first current.

10. The system of claim 1 wherein the control module transmits a report to a remote device via a network in response to occurrences of the control module disconnecting the first, second, and third phases from the motor.

11. A method for protecting a three-phase electric motor of a compressor, the motor receiving first, second, and third phases from a three-phase power supply, the method comprising:

using a line break protector, disconnecting the motor from only the first phase in response to a temperature being greater than a predetermined temperature threshold;

measuring a first current flowing through the line break protector;

determining a current value based on the first current independent of current in the second and third phases; and

disconnecting the motor from the first, second, and third phases in response to the current value being less than or equal to a predetermined threshold.

12. The method of claim 11 wherein disconnecting the motor from the first, second, and third phases is performed by actuating a three-phase interruption device that electrically disconnects the first, second, and third phases from the motor.

13. The method of claim 12 wherein the three-phase interruption device includes a contactor.

14. The method of claim 11 wherein the predetermined threshold is zero.

15. The method of claim 11 wherein the current value includes at least one of (i) a peak of the first current during a predetermined period and (ii) a root mean squared (RMS) of the first current during the predetermined period.

16. The method of claim 11 further comprising:

measuring a second current corresponding to one of the second and third phases;

selectively detecting at least one of a phase loss and a reversed phase sequence based on the first current and the second current; and

disconnecting the motor from the first, second, and third phases in response to one or more of the phase loss and the reversed phase sequence being detected.

17. The method of claim 11 wherein the temperature is responsive to heat generated by a winding of the motor during operation of the motor.

18. The method of claim 11 further comprising reconnecting the motor to the first, second, and third phases in response to a predetermined shutdown period passing subsequent to disconnecting the first, second, and third phases from the motor.

19. The method of claim 11 wherein the temperature is responsive to a magnitude of the first current.

20. The method of claim 11 further comprising transmitting a report to a remote device via a network in response to performing the disconnecting the first, second, and third phases from the motor.