Ground fault circuit interrupter using frequency recognition and measurement
A wiring device including an interrupting device, a fault detection circuit, and a testing circuit. The interrupting device is electrically connecting one or more line terminals to one or more load terminals. The fault detection circuit is configured to detect a fault condition and generate a fault detection signal in response to detecting the fault condition. The fault detection signal being provided to the interrupting device to place the interrupting device in a tripped condition. The testing circuit is configured to determine a frequency of an input voltage at the one or more line terminals, filter the frequency of the input voltage, determine whether the filtered frequency is within a predetermined range, and when the filtered frequency is within the predetermined range, perform a test of the wiring device.
1. A wiring device comprising:
an interrupting device electrically connecting one or more line terminals to one or more load terminals when the interrupting device is in a reset condition and disconnecting the line terminals from the load terminals when the interrupting device is in a tripped condition;
a fault detection circuit configured to detect a fault condition and generate a fault detection signal in response to detecting the fault condition, the fault detection signal being provided to the interrupting device to place the interrupting device in the tripped condition; and
a testing circuit configured to,
determine a frequency of an input voltage at the one or more line terminals,
filter the frequency of the input voltage,
determine whether the filtered frequency is within a predetermined range, and
when the filtered frequency is within the predetermined range, perform a test of the wiring device.
2. The wiring device of claim 1 , wherein the test is at least one selected from a group consisting of a first test of the interrupting device at a first period of the frequency, and a second test of the fault detection circuit at a second period of the frequency.
3. The wiring device of claim 2 , wherein the first period and the second period are respectively located at a negative half-wave of the frequency.
4. The wiring device of claim 2 , wherein the first period of the frequency and the second period of the frequency are equal.
5. The wiring device of claim 1 , wherein the interrupting device includes a solenoid and a solenoid switch.
6. The wiring device of claim 5 , wherein the first test includes the steps of
outputting a control signal to activate the solenoid switch; and
measuring a current of the solenoid when the control signal is output.
7. The wiring device of claim 1 , wherein the fault detection circuit includes a transformer and a detection controller.
8. The wiring device of claim 7 , wherein the second test includes the steps of
outputting a control signal to allow current to flow through the transformer; and
measuring an output of the detection controller when current is flowing through the transformer.
9. The wiring device of claim 1 , wherein determining the frequency includes counting the number of positive zero crossings of the input voltage over a predetermined time period.
10. The wiring device of claim 1 , wherein filtering the frequency of the line voltage includes a low-pass filtering operation to remove noise.
11. A method of performing a self-test of a wiring device, the method including:
determining a frequency of an input voltage;
filtering the frequency of the input voltage;
determining whether the filtered frequency of the input voltage is within a predetermined range; and
when the filtered frequency is within the predetermined range, performing the self-test of the wiring device.
12. The method of claim 11 , wherein the self-test includes at least one selected from a group consisting of a first test of an interrupting device of the wiring device at a first period of the frequency, and a second test of a fault detection circuit of the wiring device at a second period of the frequency.
13. The method of claim 12 , wherein the first period and the second period are respectively located at a negative half-wave of the frequency.
14. The method of claim 12 , wherein the first period of the frequency and the second period of the frequency are equal.
15. The method of claim 11 , wherein filtering the frequency of the line voltage includes a low-pass filtering operation to remove noise.
16. The method of claim 11 , wherein the step of performing the first test includes
outputting a control signal to activate a solenoid switch; and
measuring a current of a solenoid when the control signal is output.
17. The method of claim 11 , wherein the step of performing the second test includes
outputting a control signal to allow current to flow through a transformer; and
measuring an output of the fault detection circuit when current is flowing through the transformer.
18. The method of claim 14 , further comprising determining end-of-life of the wiring device if at least one selected from the group consisting of the first test and the second test have failed a predetermined number of times.
19. The method of claim 18 , wherein the step of determining the frequency of the input voltage includes counting the number of positive zero crossings of the input voltage over a predetermined time period.
20. The method of claim 11 , further comprising switching a buzzer on and off at a predetermined rate when a fault is detected.