Electrical safety device miswire detection

Patent metadata

Field	Value
Publication number	US-10141734-B2
Application number	US-201514850271-A
Country	US
Kind code	B2
Filing date	Sep 10, 2015
Priority date	Oct 26, 2014
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

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.

First claim

The invention claimed is:

1. An electrical safety device comprising:
a line connection input, the line connection input including a line live input and a line neutral input configured to receive an a.c. signal;
a differential current detector to be coupled with a control circuit configured to receive a sense signal from the differential current detector indicating an amount of current passing through the differential current detector on a live current path and a neutral current path;
the control circuit configured to form a test signal;
an interrupter output; and
circuitry to:
activate the test signal 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 signal is active, the sense signal to a threshold value;
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;
determine a polarity of the sense signal in response to the sense signal exceeding the threshold value; and
activate the interrupter output in response to the sense signal having a polarity that is opposite to a polarity of the a.c. signal.

2. The control circuit of claim 1 , further comprising:
the control circuit configured 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 signal in response to a first zero voltage crossing that corresponds with a first polarity of the AC voltage; and
deactivate the test signal in response to the sense signal exceeding the threshold value or a second zero voltage crossing that immediately follows the first zero voltage crossing.

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

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

5. 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;
the line live and line neutral connections configured to receive an a.c. signal:
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;
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;
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 being opposite of a polarity of the a.c. signal.

6. The electrical safety device of claim 5 ,
wherein the control circuit is further to indicate the differential current not exceeding the threshold value.

7. The electrical safety device of claim 5 , 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.

8. The electrical safety device of claim 5 , wherein the control circuit is further to provide a selectable electrical load selectable to be coupled across the live current path and the neutral current path.

9. 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 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;
the line live and line neutral connections configured to receive an a.c. signal;
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;
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;
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 being opposite of a polarity of the a.c. 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.

10. The electrical safety device of claim 5 , 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.

11. The electrical safety device of claim 5 , wherein the control circuit is configured 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.

12. The electrical safety device of claim 5 , 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.

13. The electrical safety device of claim 5 , wherein the control circuit is further to select the selectable conducting path and determine the differenti

Assignees

• Semiconductor Components Ind Llc

Inventors

• Beck Riley D
• Layton Kent D
• Grange Scott R
• Singh Rishi Pratap

Classifications

• G01R19/165

  Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values · CPC title

• H01H83/04 Primary

  with testing means for indicating the ability of the switch or relay to function properly · CPC title

• H01H83/144

  with differential transformer · CPC title

• H02H3/44 Primary

  responsive to the rate of change of electrical quantities · CPC title

• H01H2083/045

  Auxiliary switch opening testing circuit in synchronism with the main circuit · CPC title