ELECTRICAL SAFETY DEVICE MISWIRE DETECTION

• US 20160118785A1
• Filed: 09/10/2015
• Published: 04/28/2016
• Est. Priority Date: 10/26/2014
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: BECK, Riley D., LAYTON, Kent D., GRANGE, Scott R., SINGH, Rishi Pratap
• Granted Patent: US 10,141,734 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01R 19/165 Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
• CPC Class Codes: H01H 2083/045 Auxiliary switch opening testing circuit in synchronism with the main circuit
• CPC Class Codes: H01H 83/04 with testing means for indicating the ability of the switch or relay to function properly
• CPC Class Codes: H01H 83/144 with differential transformer
• CPC Class Codes: H02H 3/44 responsive to the rate of change of electrical quantities

Abstract

Aspects of an electrical safety device that provides detection of miswiring of line and load connection pairs are presented. In an example, the device includes a differential current detector through which are routed a live current path and a neutral current path coupling the line and load connection pairs. The device also includes a selectable conducting path that, when selected, circumvents the differential current detector while coupling one of a line live connection to a load live connection or a line neutral connection to a load neutral connection of the connection pairs. The device further includes a control circuit that determines, via the differential current detector, while the conducting path is selected, a differential current defined by a difference in currents on the live and neutral current paths, and interrupts at least one of the live and neutral current paths in response to the differential current not exceeding a threshold value.

Claims

1. A control circuit for an electrical safety device, the control circuit comprising:

a power supply input to receive electrical power for the control circuit;

a differential current detector input to be coupled with a differential current detector to receive a sense signal indicating an amount of current passing through the differential current detector on a live current path and a neutral current path;

a test control output;

an interrupter output; and

circuitry to;

activate the test control output to cause at least a portion of the current passing through the differential current detector on one of the live current path and the neutral current path to circumvent the differential current detector;

compare, while the test control output is active, the sense signal to a threshold value; and

activate the interrupter output in response to the sense signal not exceeding the threshold value to cause at least one of the live current path and the neutral current path to be interrupted.

2. The control circuit of claim 1, the circuitry further to:

determine a polarity of the sense signal in response to the sense signal exceeding the threshold value; and

activate the interrupter output based on the polarity of the sense signal indicating electrical power being supplied at a load live connection of the electrical safety device.

3. The control circuit of claim 1, further comprising:

a zero crossing detector to detect zero voltage crossings of an alternating current (AC) voltage across a point along the live current path and a point along the live neutral path;

wherein the circuitry is to;

activate the test control output in response to a first zero voltage crossing detected by the zero crossing detector that corresponds with a first polarity of the AC voltage; and

deactivate the test control output in response to the sense signal exceeding the threshold value or a second zero voltage crossing detected by the zero crossing detector that immediately follows the first zero voltage crossing.

4. The control circuit of claim 1, wherein the circuitry is further to activate the test control output and compare the sense signal to the threshold value in response to a power supply voltage being supplied to the control circuit.

5. The control circuit of claim 1, wherein the circuitry is further to activate the test control output and compare the sense signal to the threshold value periodically while a power supply voltage is supplied to the control circuit.

6. An electrical safety device comprising:

a live current path coupling a line live connection and a load live connection;

a neutral current path coupling a line neutral connection and a load neutral connection;

a differential current detector through which the live current path and the neutral current path are routed;

a selectable conducting path that, when selected, circumvents the differential current detector while shorting one of the line live connection to the load live connection or shorting the line neutral connection to the load neutral connection; and

a control circuit to;

select the selectable conducting path;

determine, via the differential current detector, while the selectable conducting path is selected, a differential current defined by a difference between a first current on the live current path and a second current on the neutral current path; and

interrupt at least one of the live current path and the neutral current path in response to the differential current not exceeding a threshold value.

7. The electrical safety device of claim 6,

wherein the control circuit is further to indicate the differential current not exceeding the threshold value.

8. The electrical safety device of claim 7, further comprising at least one of:

a light generation device to be employed by the control circuit to generate a visual indication indicating the differential current not exceeding the threshold value;

an audio generation device to be employed by the control circuit to generate an audio indication indicating the differential current not exceeding the threshold value; and

a communication interface to be employed by the control circuit to generate a message notification via a communication network indicating the differential current not exceeding the threshold value.

9. The electrical safety device of claim 6, the control circuit further to:

determine a polarity of the differential current in response to the differential current exceeding the threshold value; and

interrupt the at least one of the live current path and the neutral current path based on the polarity of the differential current indicating electrical power being supplied at the load live connection.

10. The electrical safety device of claim 6, the selectable conducting path comprising a field effect transistor (FET) having a resistance in an on state that is approximately equal to a resistance of at least one of the live current path and the neutral current path.

11. The electrical safety device of claim 6, wherein the control circuit is further to provide an electrical load across the live current path and the neutral current path.

12. The electrical safety device of claim 6, further comprising:

a load circuit coupled between the live current path and the neutral current path to provide an electrical load in response to a first control signal;

wherein the control circuit is to provide the first control signal to the load circuit while the selectable conducting path couples one of the line live connection to the load live connection or the line neutral connection to the load neutral connection.

13. The electrical safety device of claim 6, further comprising:

a receptacle live connection connected to the load live connection via a first current path that is not routed through the differential current detector; and

a receptacle neutral connection connected to the load neutral connection via a second current path that is not routed through the differential current detector.

14. The electrical safety device of claim 6, wherein the control circuit comprises a zero crossing detector to detect zero crossings of an AC voltage across a point along the live current path and a point along the neutral current path, and wherein the control circuit is further to:

select the selectable conducting path in response to a first detected zero crossing of the AC voltage that corresponds with a first polarity of the AC voltage; and

deselect the conducting path in response to the differential current exceeding the threshold value or a second detected zero crossing of the AC voltage that immediately follows the first detected zero crossing.

15. The electrical safety device of claim 6, wherein the control circuit is further to select the selectable conducting path and determine the differential current in response to a power supply voltage being applied to the control circuit.

16. The electrical safety device of claim 6, wherein the control circuit is further to select the selectable conducting path and determine the differential current periodically while a power supply voltage is applied to the control circuit.

17. The electrical safety device of claim 6, wherein the electrical safety device comprises at least one of a ground fault circuit interrupter, an arc fault circuit interrupter, a surge protection device, or a transient voltage surge suppressor.

18. The electrical safety device of claim 6, wherein the control circuit comprises:

a differential current detector input to be coupled with the differential current detector to receive a sense signal indicating the differential current;

a test control output to select the selectable conducting path;

a comparison circuit to compare the sense signal to a threshold while the test control output is active; and

an interrupter output to cause at least one of the live current path and the neutral current path to be interrupted in response to the sense signal not exceeding the threshold.

19. A method for detecting a miswiring of a line connection pair and a load connection pair of an electrical safety device, the method comprising:

circumventing at least a portion of an electrical current carried over one of a live current path and a neutral current path through the electrical safety device, the live current path connecting a line live connection of the line connection pair with a load live connection of the load connection pair, and the neutral current path connecting a line neutral connection of the line connection pair with a load neutral connection of the load connection pair;

determining, while circumventing the at least a portion of the electrical current, a differential current defined by a difference between the electrical current carried over the live current path and the electrical current carried over the neutral current path; and

interrupting at least one of the live current path and the neutral current path in response to the differential current not exceeding a threshold value.

20. The method of claim 19, further comprising:

determining a polarity of the differential current in response to the differential current exceeding the threshold value; and

interrupting the at least one of the live current path and the neutral current path in response to the polarity of the differential current indicating electrical power being supplied at the load live connection.