Leakage current protection device adapted to a wide variety of domestic and international applications

• US 6,381,113 B1
• Filed: 04/12/1996
• Issued: 04/30/2002
• Est. Priority Date: 07/22/1992
• Status: Expired due to Fees

• Current Assignee: Technology Research Group LLC (Southwire Company)
• Original Assignee: Technology Research Corporation (Southwire Company)
• Inventors: Legatti, Raymond H.
• Primary Examiner(s): HUYNH, KIM NGOC
• Application Number:
  US08/631,553
• Time in Patent Office: 2,209 Days
• Field of Search: 361/42, 361/44, 361/45, 361/46, 361/47, 361/94, 361/93.6
• US Class Current: 361/46
• CPC Class Codes: H02H 1/04 Arrangements for preventing response to transient abnormal conditions, e.g. to lightning or to short duration over voltage or oscillations; Damping the influence of dc component by short circuits in ac networks
• CPC Class Codes: H02H 1/06 Arrangements for supplying operative power power supply arrangements in general G05F, H02M
• CPC Class Codes: H02H 3/006 Calibration or setting of parameters
• CPC Class Codes: H02H 3/332 with means responsive to dc component in the fault current
• CPC Class Codes: H02H 3/335 the main function being self testing of the device
• CPC Class Codes: H02H 3/338 also responsive to wiring error, e.g. loss of neutral, break
• CPC Class Codes: H02H 3/347 using summation current transformers

Abstract

A leakage current protection device, such as a ground fault circuit interrupter (GFCI), is provided that can be used in single phase or polyphase systems, with a range of input voltages from 70 to 264 volts AC, frequencies of 50 or 60 hertz, and ground fault trip currents of 6 to 30 milliamperes. A leading power factor circuit is connected to the secondary winding of the GFCI differential transformer to permit the magnetic circuit to respond to pulsating DC signals. Provision is made for continuing to provide GFCI protection in the event of an open neutral lead, with a timing circuit to prevent current flow to the ground lead until current flow in the neutral lead is completely discontinued. Various types of circuit interrupting devices, such as a circuit breaker or a power converter, may be selectively utilized.

Claims

1. A leakage current protection device for use in an electrical system having a neutral lead, a ground lead and at least one power line lead extending from a source of energy to a load comprising:

a differential transformer having a core, opposed primary windings producing bucking fluxes representative of current to the load and current from the load, and a secondary winding;

circuit opening means to open the power line lead in response to a trip signal generated in said secondary winding when a leakage current above a predetermined magnitude occurs;

a supplemental secondary winding on said differential transformer;

switch means to close the circuit to said supplemental secondary winding to simulate the occurrence of a leakage current in order to test the protection device; and

time delay means to prevent current flow to the ground lead until said circuit opening means has been actuated by current flow to the neutral lead, thereby decreasing the chances that other protection devices in the electrical system would erroneously sense the test simulation as a leakage current.

2. A leakage current protection device for use in an electrical system having a neutral lead, a ground lead, and at least one power line lead extending from a source of energy to a load comprising:

a differential transformer having a core, opposed primary windings producing bucking fluxes representative of current to the load and current from the load, and a secondary winding;

circuit opening means to open the power line lead in response to a trip signal generated in said secondary winding when a leakage current above a predetermined magnitude is detected; and

a control means comprising;

a rectifier to provide DC power from the power line lead to control circuitry for the protection device;

first unidirectional current means connected from said protection device control circuitry to the neutral lead;

second unidirectional current means connected from said protection device control circuitry to ground, said second unidirectional current means having a higher forward voltage drop than said first unidirectional current means; and

third unidirectional current means connected from said protection device control circuitry to the neutral lead with a polarity opposite that of said first unidirectional current device;

said control means providing power to actuate said circuit opening means in the event of a leakage current above a predetermined magnitude whenever any two of the power line, neutral and ground leads between the power source and the protective device remain intact and a voltage in excess of a predetermined minimum potential exists between said two intact lines.

3. A leakage current protection device as claimed in claim 2 and further comprising a metal oxide varistor connected across said rectifier to provide transient voltage protection.

4. A leakage current protection device as claimed in claim 2 wherein said rectifier is a full wave rectifier for a polyphase three power line lead configuration.

5. A leakage current protection device as claimed in claim 4 wherein said full wave rectifier comprises a pair of diodes connected in series across the protection device control circuitry for each of said power line leads, with each of said power line leads connected to the midpoint of an associated pair of diodes.

6. A leakage current protection device as claimed in claim 5 wherein said first, second and third unidirectional current means comprises:

a first pair of series connected diodes located across the protection device control circuitry in parallel with said rectifier pairs of diodes, the midpoint of said first pair of diodes being connected to the neutral lead; and

a second pair of series connected diodes located across the protection device control circuitry in parallel with said rectifier pairs of diodes and said first pair of diodes, the midpoint of said second pair of diodes being connected to the ground lead.

7. A leakage current protection device for use in an electrical system having at least a neutral lead and a power line lead extending from a source of energy to a load comprising:

a differential transformer having a cores opposed primary windings producing bucking fluxes representative of current to the load and from the load, and a secondary winding;

power factor adjustment means connected across said secondary winding for tuning said differential transformer circuit to have a leading power factor, which permits the protective device to efficiently respond to pulsating DC signals over a large range of input voltages;

regulating means acting in conjunction with said power factor adjustment means to permit the protection device to efficiently and effectively respond to a range of line-to-neutral AC input voltages varying from 70 to 264 volts;

adjusting means to selectively set the protection device to respond to a leakage current in the nominal range of 6 to 30 milliamperes;

an amplifier circuit to linearly amplify the output of said secondary winding and provide a stable trip signal under varying conditions;

circuit opening means to open the power line lead in response to a trip signal being generated in said amplifier circuit as a result of a leakage current above a predetermined magnitude producing a current in said secondary winding;

a supplemental secondary coil on said differential transformer;

switch means to close the circuit to said supplemental circuit to simulate the occurrence of a leakage current in order to test the protection device; and

time delay means to prevent current flow to the ground lead until said circuit opening means has been actuated by current flow to the neutral lead, thereby decreasing the chances that other protection devices in the electrical system would erroneously sense the test simulation as a leakage current.

8. A leakage current protection device for use in an electrical system having at least a neutral lead and a power line lead extending from a source of energy to a load comprising:

a differential transformer having a core, opposed primary windings producing bucking fluxes representative of current to the load and current from the load, and a secondary winding;

power factor adjustment means comprising capacitive means for tuning the inductance of said differential transformer so that said differential transformer circuit has a leading power factor, said power factor adjustment means connected across said secondary winding for permitting the protection device to respond to pulsating DC signals;

a linear amplifier circuit to amplify the output of said secondary winding and provide a stable trip signal under varying conditions; and

circuit opening means to open the power line lead in response to a trip signal being generated in said amplifier circuit as a result of a leakage current above a predetermined magnitude producing a current in said secondary winding.

9. A leakage current protection device as claimed in claim 8 and further comprising a pair of clamping diodes connected in opposite directions across said secondary winding in parallel with said capacitive means.

10. A leakage current protection device as claimed in claim 8 and further comprising regulating means to provide a substantially constant operating voltage for said circuit opening means over a range of line-to-neutral AC input voltages of 70 to 264 volts, said capacitive means increasing the sensitivity of said differential transformer for permitting efficient and effective operation over the full range of input voltages.

11. A leakage current protection device as claimed in claim 8 and further comprising adjusting means to selectively set the protection device to respond to a leakage current in the nominal range of 6 to 30 milliamperes.

12. A leakage current protection device as claimed in claim 8 and further comprising:

a supplemental secondary winding on said differential transformer; and

switch means to close the circuit to said supplemental secondary winding to simulate the occurrence of a leakage current in order to test the protection device.

13. A leakage current protection device for use in an electrical system having a neutral lead, a ground lead, and at least one power line lead extending from a source of energy to a load comprising:

a differential transformer having a core, opposed primary/windings producing bucking fluxes representative of current to the load and current from the load, and a secondary winding;

circuit opening means to open the power line lead in response to a trip signal generated in said secondary winding when a leakage current above a predetermined magnitude is detected; and

control means to provide power to actuate said circuit opening means in the event of a leakage current above a predetermined magnitude whenever the power line lead is broken and the ground lead and the neutral lead are intact, and when the ground lead is broken and the power line lead and the neutral lead remain intact, and when the neutral lead is broken and the power line lead and the ground line remain intact, and a voltage in excess of a predetermined minimum potential exists between said two intact leads.

14. A leakage current protection device as claimed in claim 13 and further comprising regulating means to provide a substantially constant operating voltage for said circuit opening means over a range of line-to-neutral AC input voltages of 70 to 264 volts.

15. A leakage current protection device as claimed in claim 14 and further comprising means to selectively set the protection device to respond to leakage current in the nominal range of 6 to 30 milliamperes.

16. A leakage current protection device as claimed in claim 13 and further comprising adjusting means to set the protection device to respond to leakage current in the range of 6 to 30 milliamperes.

17. A leakage current protection device as claimed in claim 13 wherein said circuit opening means comprises:

a circuit breaker connected to open the power line lead when energized;

a contactor to open the power line lead when de-energized;

connector means for alternatively selectively connecting a single one of said circuit breaker and said contactor to a regulated voltage power supply in the protection device; and

switch means responsive to a trip signal generated in said secondary winding when leakage current above a predetermined magnitude occurs, said switch means energizing said circuit breaker when it is connected and for de-energizing said contactor when it is connected.

18. A leakage current protection device as claimed in claim 17 and further comprising regulating means to provide a substantially constant operating voltage for said circuit opening means over a range of line-to-neutral AC input voltages of 70 to 264 volts.

19. A leakage current protection device as claimed in claim 18 and further comprising adjusting means to set the protection device to respond to a leakage current in the nominal range of 6 to 30 milliamperes.

20. A leakage current protection device claimed in claim 17 and further comprising adjusting means to set the protection device to respond to a leakage current in the nominal range of 6 to 30 milliamperes.

21. A leakage current protection device for use in an electrical system having a neutral lead, a ground lead, and at least one power line extending from a source of energy to a load comprising:

a differential transformer having a core, opposed primary windings producing bucking fluxes representative of current to the load and current from the load, and a secondary winding;

a supplemental secondary coil on said differential transformer;

switch means to close the circuit to said supplemental secondary winding to simulate the occurrence of a leakage current in order to test the protection device;

circuit opening means to open the power line lead in response to a trip signal generated in said secondary winding when a leakage current above a predetermined magnitude is detected, said circuit opening means including;

a circuit breaker connected to open the power line lead when energized;

a contactor to open the power line lead when de-energized;

connector means for alternatively selectively connecting a single one of said circuit breaker and said contactor to a regulated voltage supply in the protection device;

switch means responsive to a trip signal generated in said secondary winding when a leakage current above a predetermined magnitude occurs, said switch means energizing said circuit breaker when it is connected and de-energizing said contactor when it is connected; and

control means to provide power to actuate said circuit opening means in the event of a leakage current above a predetermined magnitude whenever any two of the power line, neutral and ground leads between the power source and the protection device remain intact and a voltage in excess of a predetermined minimum potential exists between said two intact lines; and

time delay means to prevent current flow to the ground lead until said circuit opening means has been actuated by current flow to the neutral lead, thereby decreasing the chances that other protection devices in the electrical system would erroneously sense the test simulation as a leakage current above a predetermined magnitude.

22. A leakage protection device as claimed in claim 21 and further comprising adjusting means to set the protection device to respond to a leakage current in the nominal range of 6 to 30 milliamperes.

23. A leakage current protection device as claimed in claim 22 and further comprising regulating means to provide a substantially constant operating voltage for said circuit opening means over a range of line-to-neutral AC input voltages of 70 to 264 volts.

24. A leakage current protection device for use with either a single phase or a polyphase power system having a neutral lead, a ground lead and at least one power line lead extending from a source of energy to a load comprising:

a differential transformer having a core, opposed primary windings producing bucking fluxes representative of current to the load and current from the load, and a secondary winding;

connecting means to ensure that either a single phase or polyphase input will properly energize the protection device;

circuit opening means to open all power line leads in response to a trip signal generated in said secondary winding when a leakage current above a predetermined magnitude occurs; and

control means to provide power to actuate said circuit opening means in the event of a leakage current above a predetermined magnitude whenever a power line lead is broken, and the ground lead and the neutral lead are intact, and when the ground lead is broken and a power line lead and the neutral lead remain intact, and when the neutral lead is broken and a power line lead and the ground line remain intact and a voltage in excess or a predetermined minimum potential exists between said two intact leads.

25. A leakage current protection device for use in an electrical system having a neutral lead, a ground lead, and at least one power line extending from a source of energy to a load comprising:

a differential transformer having a core, opposed primary windings producing bucking fluxes representative of current to the load and current from the load, and a secondary winding;

a supplemental secondary winding on said differential transformer;

switch means to close the circuit to said supplemental secondary winding to simulate the occurrence of a leakage current in order to test the protection device;

circuit opening means to open the power line lead in response to a trip signal generated in said secondary winding when a leakage current above a predetermined magnitude is detected;

control means to provide power to actuate said circuit opening means in the event of a leakage current above a predetermined magnitude whenever any two of the power line, neutral and ground leads between the power source and the protection device remain intact and a voltage in excess of a predetermined minimum potential exists between said two intact lines; and

time delay means to prevent current flow to the ground lead until said circuit opening means has been actuated by current flow to the neutral lead, thereby decreasing the chances that other protection devices in the electrical system would erroneously sense the presence of a leakage current above a predetermined magnitude if the neutral lead is unbroken.

26. A leakage current protection device as claimed in claim 25 and further comprising adjusting means to set the protection device to respond to a leakage current in the nominal range of 6 to 30 milliamperes.

27. A leakage current protection device claimed in claim 26 and further comprising regulating means to provide a substantially constant operating voltage for said circuit opening means over a range of line-to-neutral AC input voltages of 70 to 264 volts.