Leakage current interrupter with sustained overvoltage and/or overcurrent protection

• US 7,292,418 B2
• Filed: 04/27/2004
• Issued: 11/06/2007
• Est. Priority Date: 04/27/2004
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Egner, J. David
• Primary Examiner(s): Leja; Ronald W.
• Application Number:
  US10/832,412
• Publication Number:
  US 20050237680A1
• Time in Patent Office: 1,288 Days
• Field of Search: 361/42
• US Class Current: 361/42
• CPC Class Codes: H02H 3/08 responsive to excess current responsive to abnormal temperature caused by excess current H02H5/04
• CPC Class Codes: H02H 3/20 responsive to excess voltage
• CPC Class Codes: H02H 3/33 using summation current transformers H02H3/347 takes precedence

Abstract

An appliance leakage current interrupter (ALCI) includes components for preventing sustained over-voltage and sustained over-current conditions. A current interruption threshold is inversely proportional to voltage supplied to the appliance. A microprocessor measures the voltage level of the incoming AC mains supply. The microprocessor is coupled to a sub-circuit for intentionally inducing a current mismatch between the two power lines monitored by the ALCI. Upon detecting an over-voltage of sufficient magnitude and duration, the microprocessor induces a current mismatch in the power lines, thereby causing the ALCI to interrupt power. A second current sensing transformer monitors one of the power lines. The microprocessor also receives the output of the second current sensing transformer. Upon detecting a current level exceeding a variable threshold, the microprocessor induces a current mismatch in the power lines and causes the ALCI to interrupt power.

Claims

1. A circuit for interrupting power to an appliance, comprising:

a current detector providing an imbalance signal when current through first and second power supply lines is unbalanced by more than a predetermined amount;

an interruption switch for interrupting current flow through at least one of the first and second supply lines;

a ground fault detection sub-circuit configured to open the interruption switch upon receipt of the imbalance signal;

a fault-inducing switch connecting the first and second supply lines and causing a current imbalance between the first and second supply lines when closed;

an over-voltage detection sub-circuit configured to receive a signal indicative of voltage supplied to the appliance, and further configured to close the fault-inducing switch when the supplied voltage exceeds a voltage threshold V_TRIP;

at least one TEST switch, the closure of which causes the over-voltage detection sub-circuit to receive a signal indicative of a supplied voltage exceeding V_TRIP; and

at least one externally visible light-emitting component, and wherein the over-voltage detection sub-circuit is further configured;

to determine, upon closure of the TEST switch, whether a signal corresponding to a supplied voltage exceeding V_TRIP has been detected,

to close the fault-inducing switch upon determining that a signal corresponding to a supplied voltage exceeding V_TRIP has been detected, and

to activate the at least one light-emitting component so as to indicate a malfunction upon determining that a signal corresponding to a supplied voltage exceeding V_TRIP has not been detected.

2. The circuit of claim 1, further comprising:

a surge protector sub-circuit operably positioned across said first and second power supply lines.

3. The circuit of claim 1, further comprising:

a microprocessor configured to automatically test the over-voltage sub-circuit and to indicate a malfunction when the test determines that there is a malfunction.

4. A circuit for interrupting power to an appliance, comprising:

a current detector providing an imbalance signal when current through first and second power supply lines is unbalanced by more than a predetermined amount;

at least one interruption switch for interrupting current flow through at least one of the first and second supply lines;

a ground fault detection sub-circuit configured to open the at least one interruption switch upon receipt of the imbalance signal;

a fault-inducing switch connecting the first and second supply lines and causing a current imbalance between the first and second supply lines when closed; and

an over-current detection sub-circuit configured to receive a signal indicative of current supplied to the appliance, and further configured to close the fault-inducing switch when the supplied current exceeds a current threshold A_TRIP;

wherein the over-current detection sub-circuit is also configured to receive a signal indicative of voltage supplied to the appliance, and wherein A_TRIP has a value that varies based on the supplied voltage.

5. The circuit of claim 4, wherein A_TRIP is inversely proportional to the supplied voltage over a range of supplied voltage values.

6. The circuit of claim 4, further comprising:

a surge protector sub-circuit operably positioned across said first and second power supply lines.

7. The circuit of claim 4, further comprising:

a microprocessor configured to automatically test the over-current sub-circuit and to indicate a malfunction when the test determines that there is a malfunction.

8. A circuit for interrupting power to an appliance, comprising:

a current detector providing an imbalance signal when current through first and second power supply lines is unbalanced by more than a predetermined amount;

at least one interruption switch for interrupting current flow through at least one of the first and second supply lines;

a ground fault detection sub-circuit configured to open the at least one interruption switch upon receipt of the imbalance signal;

a fault-inducing switch connecting the first and second supply lines and causing a current imbalance between the first and second supply lines when closed; and

an over-current detection sub-circuit configured to receive a signal indicative of current supplied to the appliance, and further configured to close the fault-inducing switch when the supplied current exceeds a current threshold A_TRIP;

wherein the over-current detection sub-circuit is further configured to close the fault-inducing switch when the supplied current exceeds a current threshold A_TRIP for a period of time t<sub>A—

TRIP</sub>;

wherein the over-current detection sub-circuit is also configured to receive a signal indicative of voltage supplied to the appliance, and

wherein A_TRIP has a value that varies based on the supplied voltage.

9. The circuit of claim 8, wherein t_A-TRIP exceeds 100 milliseconds.

10. The circuit of claim 8, wherein t_A-TRIP exceeds 150 milliseconds.

11. The circuit of claim 8, wherein t_A-TRIP exceeds 200 milliseconds.

12. The circuit of claim 8, wherein A_TRIP is inversely proportional to the supplied voltage over a range of supplied voltage values.

13. The circuit of claim 8, wherein the over-current detection sub-circuit comprises a microprocessor configured to determined whether the supplied current has exceeded A_TRIP for a period of time t_A-Trip, and to close the fault-inducing switch upon making said determination.

14. The circuit of claim 8, further comprising:

a surge protector sub-circuit operably positioned across said fist and second power supply lines.

15. The circuit of claim 8, further comprising:

a microprocessor configured to automatically test the over-current sub-circuit and to indicate a malfunction when the test determines that there is a malfunction.

16. A circuit for interrupting power to an appliance, comprising:

a current detector providing an imbalance signal when current though first and second power supply lines is unbalanced by more than a predetermined amount;

at least one interruption switch for interrupting current flow through at least one of the first and second supply lines;

a ground fault detection sub-circuit configured to open the at least one interruption switch upon receipt of the imbalance signal;

a fault-inducing switch connecting the first and second supply lines and causing a current imbalance between the first and second supply lines when closed; and

an over-current detection sub-circuit configured to receive a signal indicative of current supplied to the appliance, and further configured to close the fault-inducing switch when the supplied current exceeds a current threshold A_TRIP;

at least one TEST switch, the closure of which causes the over-current detection sub-circuit to receive a signal indicative of supplied current exceeding A_TRIP; and

at least one externally-visible light-emitting component, and wherein the over-current detection sub-circuit is further configured;

to determine, upon closure of the TEST switch, whether a signal corresponding to a supplied current exceeding A_TRIP has been detected,

to close the fault-inducing switch upon determining that a signal corresponding to a supplied current exceeding A_TRIP has been detected, and

to activate the at least one light-emitting component so as to indicate a malfunction upon determining that a signal corresponding to a supplied current exceeding A_TRIP has not been detected.

17. The circuit of claim 16, further comprising:

a surge protector sub-circuit operably positioned across said first and second power supply lines.

18. The circuit of claim 16, further comprising:

a microprocessor configured to automatically test the over-current sub-circuit and to indicate a malfunction when the test determines that there is a malfunction.

19. A circuit for interrupting power to an appliance, comprising:

a current detector providing an imbalance signal when current through first and second power supply lines is unbalanced by more than a predetermined amount;

at least one interruption switch for interrupting current flow through at least one of the first and second supply lines;

a ground fault detection sub-circuit configured to open the at least one interruption switch upon receipt of the imbalance signal;

a fault-inducing switch connecting the first and second supply lines and causing a current imbalance between the first and second supply lines when closed; and

an over-current detection sub-circuit configured to receive a signal indicative of current supplied to the appliance, and further configured to close the fault-inducing switch when the supplied current exceeds a current threshold A_TRIP;

an over-voltage detection subcircuit configured to receive a signal indicative of voltage supplied to the appliance, and further configured to close the fault-inducing switch when the supplied voltage exceeds a voltage threshold V_TRIP;

wherein the over-current detection sub-circuit is also configured to receive a signal indicative of voltage supplied to the appliance, and

wherein A_TRIP has a value that varies based on the supplied voltage.

20. The circuit of claim 19, wherein the over-voltage detection sub-circuit is further configured to close the fault-inducing switch when the supplied voltage exceeds V_TRIP for a period of time t_V-TRIP.

21. The circuit of claim 19, wherein A_TRIP is inversely proportional to the supplied voltage over a range of supplied voltage values.

22. The circuit of claim 19, further comprising:

a surge protector sub-circuit operably positioned across said first and second power supply lines.

23. The circuit of claim 19, further comprising:

a microprocessor configured to automatically test the over-voltage and over-current sub-circuits and to indicate a malfunction when the test determines that there is a malfunction.

24. A circuit for interrupting power to an appliance, comprising:

a current detector providing an imbalance signal when current through first and second power supply lines is unbalanced by more than a predetermined amount;

at least one interruption switch for interrupting current flow through at least one of the first and second supply lines;

a ground fault detection sub-circuit configured to open the at least one interruption switch upon receipt of the imbalance signal;

a fault-inducing switch connecting the first and second supply lines and causing a current imbalance between the first and second supply lines when closed; and

an over-current detection sub-circuit configured to receive a signal indicative of current supplied to the appliance, and further configured to close the fault-inducing switch when the supplied current exceeds a current threshold A_TRIP;

said circuit further comprising an over-voltage detection subcircuit configured to receive a signal indicative of voltage supplied to the appliance, and further configured to close the fault-inducing switch when the supplied voltage exceeds a voltage threshold V_TRIP;

at least one TEST switch, the closure of which causes the over-voltage detection sub-circuit to receive a signal indicative of a supplied voltage exceeding V_TRIP and the over-current detection sub-circuit to receive a signal indicative of a supplied current exceeding A_TRIP; and

at least one externally-visible light-emitting component, and wherein the over-voltage detection and over-current detection sub-circuits are further configured;

to determine, upon closure of the TEST switch, whether signals indicative of a supplied voltage exceeding V_TRIP and a supplied current exceeding A_TRIP have been detected,

to close the fault-inducing switch upon determining that signals indicative of a supplied voltage exceeding V_TRIP and a supplied current exceeding A_TRIP have been detected, and

to activate the at least one light-emitting component so as to indicate a malfunction upon determining that a signal indicative of a supplied voltage exceeding V_TRIP has not been detected or that a signal indicative of a supplied current exceeding A_TRIP has not been detected.

25. The circuit of claim 24, further comprising:

a surge protector sub-circuit operably positioned across said first and second power supply lines.

26. The circuit of claim 24, further comprising:

a microprocessor configured to automatically test the over-voltage and over-current sub-circuits and to indicate a malfunction when the test determines that there is a malfunction.

27. A circuit for interrupting power to an appliance, comprising:

an interruption switch for interrupting current flow through at least one of first and second supply lines supplying power to an appliance;

an over-voltage detection sub-circuit configured to receive a signal indicative of voltage supplied to the appliance, and further configured to open the interruption switch when the supplied voltage exceeds a voltage threshold V_TRIP for a period of time t<sub>V—

TRIP</sub>; and

an over-current detection sub-circuit configured to receive a signal indicative of current supplied to the appliance, and further configured to open the interruption switch when the supplied current exceeds a current threshold A_TRIP for a period of time t<sub>A—

TRIP</sub>;

wherein the over-current detection sub-circuit is also configured to receive a signal indicative of voltage supplied to the appliance, and wherein A_TRIP has a value that varies based on the supplied voltage.

28. The circuit of claim 27, wherein A_TRIP is inversely proportional to the supplied voltage over a range of supplied voltage values.

29. The circuit of claim 27, wherein:

the over-voltage detection sub-circuit comprises a microprocessor configured to determine whether the supplied voltage has exceeded V_TRIP for t<sub>V—

TRIP</sub>, and to open the interruption switch upon making said determination, and

the over-current detection sub-circuit comprises a microprocessor configured to determine whether the supplied current has exceeded A_TRIP for t<sub>A—

TRIP</sub>, and to open the interruption switch upon making said determination.

30. The circuit of claim 27, further comprising:

a surge protector sub-circuit operably positioned across said first and second supply lines supplying power to the appliance.

31. The microprocessor of claim 27, wherein the microprocessor is further configured to automatically test the over-voltage and over-current sub-circuits and to indicate a malfunction when the test determines that there is a malfunction.

32. A circuit for interrupting power to an appliance, comprising:

an interruption switch for interrupting current flow through at least one of first and second supply lines supplying power to an appliance;

an over-voltage detection sub-circuit configured to receive a signal indicative of voltage supplied to the appliance, and further configured to open the interruption switch when the supplied voltage exceeds a voltage threshold V_TRIP for a period of time t<sub>V—

TRIP</sub>;

an over-current detection sub-circuit configured to receive a signal indicative of current supplied to the appliance, and further configured to open the interruption switch when the supplied current exceeds a current threshold A_TRIP for a period of time t<sub>A—

TRIP</sub>;

at least one TEST switch, the closure of which causes the over-voltage detection sub-circuit to receive a signal indicative of a supplied voltage exceeding V_TRIP and the over-current detection sub-circuit to receive a signal indicative of a supplied current exceeding A_TRIP; and

at least one externally-visible light-emitting component, and wherein the over-voltage detection and over-current detection sub-circuits are further configured;

to determine, upon closure of the TEST switch, whether signals indicative of a supplied voltage exceeding V_TRIP and a supplied current exceeding A_TRIP have been detected,

to open the interruption switch upon determining that signals indicative of a supplied voltage exceeding V_TRIP and a supplied current exceeding A_TRIP have been detected, and

to activate the at least one light-emitting component so as to indicate a malfunction upon determining that a signal indicative of a supplied voltage exceeding V_TRIP has not been detected or that a signal indicative of a supplied current exceeding A_TRIP has not been detected.

33. The circuit of claim 32, further comprising:

a surge protector sub-circuit operably positioned across said first and second supply lines supplying power to the appliance.

34. The circuit of claim 32, further comprising:

a microprocessor configured to automatically test the over-voltage and over-current sub-circuits and to indicate a malfunction when the test determines that there is a malfunction.