Interruption circuit with improved shield
View Patent ↗An interrupter circuit is disclosed for interrupting power in a power cable from a power source. The power cable comprises an insulated line wire and an insulated neutral wire with a conductive shield surrounding the line wire and the neutral wire. A non-insulated drain wire contacts the conductive shield. An outer insulating layer is molded about the conductive shield. A disconnect switch is interposed between the power source and the power cable with a disconnect switch driver controlling the disconnect switch. A sensing circuit is connected between the drain wire and the disconnect switch driver for sensing a leakage current between the conductive shield and one of the insulated line wire and the insulated neutral wire for opening the disconnect switch for disconnecting the power cable from the power source.
1. An interrupter circuit for interrupting power from a power source, comprising
a power cable comprising an insulated line wire and an insulated neutral wire;
said power cable having a conductive shield surrounding said insulated line wire and said insulated neutral wire;
a drain wire having a first and a second portion;
said first portion of said drain wire being non-insulated and in contact with said conductive shield;
an outer insulating layer molded about said conductive shield;
a disconnect switch interposed between the power source and said power cable;
a disconnect switch driver for controlling said disconnect switch;
a sensing circuit comprising a differential transformer including a transformer core having a core opening;
a first primary winding comprising said insulated line wire and said insulated neutral wire extending through said core opening;
a secondary winding wound about said transformer core connected to said disconnect switch driver for opening said disconnect switch upon said secondary winding detecting an imbalance in the magnetic flux in said transformer core;
a voltage divider circuit connected across one of said power source and said power cable for providing a voltage node; and
a second primary winding wound about said transformer core interconnecting said second portion of said drain wire and said voltage node for creating an imbalance in the magnetic flux in said transformer core upon sensing a leakage current between said conductive shield and one of said insulated line wire and said insulated neutral wire for opening said disconnect switch for disconnecting said power cable from the power source.
2. An interrupter circuit as set forth in claim 1 , wherein said conductive shield is a metallic foil.
3. An interrupter circuit as set forth in claim 1 , wherein said conductive shield comprises a metallic mesh.
4. An interrupter circuit as set forth in claim 1 , wherein said conductive shield comprises a polymeric material with a metallic conductive coating.
5. An interrupter circuit as set forth in claim 1 , wherein said conductive shield comprises an organic conductive polymeric material.
6. An interrupter circuit as set forth in claim 1 , wherein said first portion of said drain wire extends along substantially the total length of said conductive shield.
7. An interrupter circuit as set forth in claim 1 , wherein said drain wire is located internal to said conductive shield.
8. An interrupter circuit as set forth in claim 1 , wherein said drain wire is located external to said conductive shield.
9. An interrupter circuit as set forth in claim 1 , wherein said outer insulating layer establishes a mechanical engagement between said first portion of said drain wire and said conductive shield to provide an electrical connection between said drain wire and said conductive shield.
10. An interrupter circuit as set forth in claim 1 , wherein said outer insulating layer establishes a resilient mechanical engagement between said first portion of said drain wire and said conductive shield to provide an electrical connection between said drain wire and said conductive shield.
11. An interrupter circuit as set forth in claim 1 , including a housing having a line lug and a neutral lug for insertion within a line socket and a neutral socket and said ground socket of the power source; and
said disconnect switch and said sensing circuit and said disconnect switch driver being located with in said housing.
12. An interrupter circuit as set forth in claim 1 , including a housing molded from a polymeric material;
a line lug and a neutral lug extending from said housing for insertion within a line socket and
a neutral socket of the power source; and
said disconnect switch and said sensing circuit and said disconnect switch driver being located with in said housing.
13. An interrupter circuit as set forth in claim 1 , wherein said disconnect switch comprises a disconnect switch coil for changing said disconnect switch from a closed position connecting said power cable to the power source and an open position for disconnecting said power cable from the power source; and
said disconnect switch driver interconnecting said sensing circuit with said disconnect switch coil for changing said disconnect switch into said open position upon said sensing circuit sensing said leakage current for disconnecting said power cable from the power source.
14. An interrupter circuit as set forth in claim 1 , wherein said disconnect switch driver comprises a thyristor connected in series with said disconnect switch for changing said disconnect switch into said open position upon conduction of said thyristor.
15. An interrupter circuit as set forth in claim 1 , wherein said disconnect switch driver comprises a thyristor connected to said disconnect switch; and
an amplifier interposed between said sensing circuit and said thyristor of said disconnect switch driver for changing said disconnect switch into said open position upon conduction of said thyristor.
16. An interrupter circuit for disconnecting a power source from a load, the power source having a line socket and a neutral socket, comprising:
a housing having a line lug and a neutral lug for insertion within said line socket and said neutral socket of the power source;
a power cord comprising an insulated line wire and an insulated neutral wire;
said power cord having a conductive shield surrounding said insulated line wire and said insulated neutral wire;
a non-insulated drain wire contacting said conductive shield;
an outer insulating layer molded about said conductive shield;
a disconnect switch located in said housing interconnecting said line lug and said neutral lug of said housing to said insulated line wire and said insulated neutral wire of said power cord;
said disconnect switch having a closed position whereat the power source is connected to the load and having an open position whereat the power source is disconnected from the load;
a disconnect switch driver located in said housing for controlling said disconnect switch; and
a sensing circuit located in said housing comprising a differential transformer including a transformer core having a core opening;
a first primary winding comprising said insulated line wire and said insulated neutral wire extending through said core opening;
a secondary winding wound about said transformer core connected to said disconnect switch driver for opening said disconnect switch upon said secondary winding detecting an imbalance in the magnetic flux in said transformer core;
a resistive voltage divider circuit connected across one of said power source and said power cable for providing a voltage node; and
a second primary winding wound about said transformer core interconnecting said non-insulated drain wire and said voltage node for creating an imbalance in the magnetic flux in said transformer core for changing said disconnect switch into said open position upon a leakage current between said conductive shield and one of said insulated line wire and said insulated neutral wire to disconnect said power cord from the power source.