Ground fault interrupter

• US 20010036048A1
• Filed: 03/15/2001
• Published: 11/01/2001
• Est. Priority Date: 03/15/2000
• Status: Active Grant

• Current Assignee: Panasonic Electric Works Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Inventors: Goto, Kiyoshi, Ishigami, Yoshihisa, Kunimoto, Yoichi
• Granted Patent: US 6,721,151 B2
• Time in Patent Office: Days
• US Class Current: 361/42
• 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 3/33 using summation current transformers H02H3/347 takes precedence
• CPC Class Codes: H02H 3/331 responsive to earthing of the neutral conductor H02H3/338 takes precedence

Abstract

A ground fault interrupter including a zero-phase current transformer configured to detect unbalanced current flowing in electric lines. A switch is provided in the electric lines. A detection resistor is connected in parallel to the zero-phase current transformer and configured to convert current outputted from the zero-phase current transformer to voltage. A controller is configured to determine based on the voltage of the detection resistor whether an electric leak occurs and to open the switch when the controller determines that an electric leak occurs. At least one filter is provided between the detection resistor and the controller and is configured to remove high frequency elements in the voltage of the resistor. The at least one filter includes an input side resistor connected in series to the controller and configured to limit current input to the controller; and a capacitor connected in parallel to the controller.

Claims

1. A ground fault interrupter, comprising:

a switch provided in electric lines connecting an electric power source and an electric load;

a zero-phase current transformer configured to detect unbalanced current flowing in the electric lines;

a detection resistor connected in parallel to the zero-phase current transformer and configured to convert current outputted from the zero-phase current transformer to voltage;

a controller configured to determine based on the voltage of the detection resistor whether an electric leak occurs and configured to open the switch when the controller determines that an electric leak occurs; and

at least one filter provided between the detection resistor and the controller and configured to remove high frequency elements in the voltage of the resistor, the at least one filter comprising;

an input side resistor connected in series to the controller and configured to limit current input to the controller; and

a capacitor connected in parallel to the controller.

2. A ground fault interrupter according to

claim 1

, wherein a resistance value of the input side resistor and a capacitance value of the capacitor are determined such that the controller determines that an electric leak occurs when a ground fault actually occurs and determines that an electric leak does not occur when a ground fault actually does not occur.

3. A ground fault interrupter according to

claim 1

, wherein a resistance value of the input side resistor and a capacitance value of the capacitor are determined such that the filter passes only elements in the voltage of the resistor having frequency between 0 and approximately 200 (Hz).

4. A ground fault interrupter according to

claim 1

, wherein the controller is configured to determine that an electric leak occurs when the voltage of the detection resistor is higher than a predetermined threshold value.

5. A ground fault interrupter according to

claim 1

, further comprising:

an additional current transformer configured to detect grounding; and

an alternating-current electric source configured to supply current to the additional current transformer to energize the additional current transformer.

6. A ground fault interrupter according to

claim 5

, wherein the alternating-current electric source comprises:

a rectifier configured to rectify alternating-current; and

an oscillator configured to generate alternating-current from the rectified alternating-current.

7. A ground fault interrupter according to

claim 5

, wherein the filter is configured to cut current having a frequency higher than a frequency of the alternating-current electric source.

8. A ground fault interrupter according to

claim 1

, further comprising:

an additional current transformer configured to detect grounding; and

a rectifier configured to rectify alternating-current and connected to the additional current transformer via a coupling capacitor.

9. A ground fault interrupter according to

claim 1

, further comprising:

an additional current transformer configured to detect grounding; and

a coupling capacitor which connects the additional current transformer and a commercial electric source.

10. A ground fault interrupter according to

claim 1

, wherein the controller is configured to determine that an electric leak occurs when the voltage of the detection resistor is higher than a predetermined reference value which is lower than a predetermined threshold value to open the switch before an electric leak actually occurs.

11. A ground fault interrupter, comprising:

a switch provided in electric lines connecting an electric power source and an electric load;

a zero-phase current transformer configured to detect unbalanced current flowing in the electric lines;

a detection resistor connected in parallel to the zero-phase current transformer and configured to convert current outputted from the zero-phase current transformer to voltage;

a controller configured to open the switch when an electric leak is detected based on the voltage of the detection resistor; and

at least one filter provided between the detection resistor and the controller and configured to remove high frequency elements in the voltage of the resistor, the at least one filter comprising;

an input side resistor connected in series to the controller and configured to limit current input to the controller; and

a capacitor connected in parallel to the controller.

12. A ground fault interrupter, comprising:

a switch provided in electric lines connecting an electric power source and an electric load;

zero-phase current transforming means for detecting unbalanced current flowing in the electric lines;

detection means for converting current outputted from the zero-phase current transforming means to voltage, the detection means being connected in parallel to the zero-phase current transforming means;

controlling means for determining based on the voltage of the detection means whether an electric leak occurs and for opening the switch when the controlling means determines that an electric leak occurs; and

at least one filter means for removing high frequency elements in the voltage of the detection means and provided between the detection means and the controlling means, the at least one filter means comprising;

an input side resistor connected in series to the controlling means and configured to limit current input to the controlling means; and

a capacitor connected in parallel to the controlling means.