Solenoid coil having an enhanced magnetic field

Abstract

An improved solenoid having an enhanced magnetic field and failsafe operation is provided, wherein a primary winding and a secondary winding are constructed such that the combined force imparted on a plunger by both windings energized together is greater than the sum of the forces imparted by the primary and secondary windings energized separately, resulting in a smaller solenoid capable of providing a predetermined force, and providing a solenoid capable of tripping a circuit interrupting latch even if one of the windings is broken.

Claims

1. A solenoid comprising: a bobbin having a hollow center with a plunger therein; a primary winding including 34 AWG wire, the primary winding having a starting end and a terminating end, wound on said bobbin and imparting a first magnetic force on said plunger when said primary winding is electrically energized, the first magnetic force being greater than a predetermined force; and a secondary winding including 33 AWG wire, the secondary winding having a starting end and a terminating end, wound on top of said primary winding and imparting a second magnetic force on said plunger when said secondary winding is electrically energized, the second magnetic force being greater than the predetermined force; wherein said primary winding and said secondary winding are configured to be in a first state, a second state, and a third state, wherein when in the first state the primary winding is energized and the secondary winding is not energized, wherein when in the second state said secondary winding is energized and said primary winding is not energized, and wherein when in the third state said primary and secondary windings are energized together, wherein when said primary and secondary windings are energized together, a third magnetic force is imparted on said plunger that is greater than the combination of said first and second magnetic forces, wherein the third magnetic force is at least 40% greater than the combination of the first and second magnetic forces; wherein a second layer is wound on top of a first layer, said first layer including of a first portion of said primary winding and said second layer including a second portion of said primary winding and a first portion of said secondary winding.

2. The solenoid of claim 1, wherein the predetermined force is sufficient to trip a circuit interrupting latch of a ground fault circuit interrupter.

3. The solenoid of claim 1, wherein the predetermined force is between 1.5 and 1.6 lbs.

4. The solenoid of claim 1, wherein the predetermined force is between 1.35 and 1.5 lbs.

5. The solenoid of claim 1, wherein the predetermined force is greater than 4.4 lbs.

6. A method of forming a solenoid comprising a bobbin having a hollow center with a plunger therein comprising the steps of winding a primary winding onto said bobbin, the primary winding including 34 AWG wire and being sufficient to impart a first magnetic force on said plunger when said primary winding is electrically energized, the first magnetic force being greater than a predetermined force; and winding a secondary winding on top of said primary winding, the secondary winding including 33 AWG wire and being sufficient to impart a second magnetic force on said plunger when said secondary winding is electrically energized, the second magnetic force being greater than the predetermined force; wherein said primary winding and secondary windings are configured to be in a first state, a second state, and a third state, wherein when in the first state the primary winding is energized and the secondary winding is not energized, wherein when in the second state said secondary winding is energized and said primary winding is not energized, and wherein when in the third state said primary and secondary windings are energized together, wherein when said primary and secondary windings are energized together, a third magnetic force is imparted on said plunger that is greater than the combination of said first and second magnetic forces, wherein the third magnetic force is at least 40% greater than the combination of the first and second magnetic forces; wherein a second layer is wound on top of a first layer, said first layer including of a first portion of said primary winding and said second layer including a second portion of said primary winding and a first portion of said secondary winding.

7. The method of claim 6, wherein said first gauge has a smaller diameter than said second gauge.

8. The method of claim 6, wherein the predetermined force is sufficient to trip a circuit interrupting latch of a ground fault circuit interrupter.

9. A method of operating a solenoid comprising a bobbin having a hollow center with a plunger therein comprising the steps of winding a primary winding onto said bobbin, the primary winding including 34 AWG wire and being sufficient to impart a first magnetic force on said plunger when said primary winding is individually electrically energized in a first state, the first magnetic force being greater than a predetermined force; winding a secondary winding on top of said primary winding, the secondary winding including 33 AWG wire and being sufficient to impart a second magnetic force on said plunger when said secondary winding is individually electrically energized in a second state, the second magnetic force being greater than the predetermined force; and energizing the primary and secondary windings together when the primary and secondary windings are each unbroken in a third state, thereby imparting a third magnetic force on said plunger, the third magnetic force being greater than the combination of said first and second magnetic forces; and if said secondary winding is broken, energizing said primary winding in the first state and not energizing said secondary winding, to impart said first magnetic force on said plunger and if said primary winding is broken, energizing said secondary winding in the second state and not energizing said primary winding, to impart said second magnetic force on said plunger, wherein the third magnetic force is at least 40% greater than the combination of the first and second magnetic forces; wherein a second layer is wound on top of a first layer, said first layer including of a first portion of said primary winding and said second layer including a second portion of said primary winding and a first portion of said secondary winding.

10. The method of claim 9, wherein the predetermined force is sufficient to trip a circuit interrupting latch of a ground fault circuit interrupter.

11. The method of claim 9, wherein the first magnetic force is between 1.35 and 1.5 lbs.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) These and other features and advantages of the present invention will become more apparent from the detailed description of exemplary embodiments with reference to the attached drawings in which:

(2) FIG. 1 is a diagram illustrating a first coil according to a first embodiment of the present invention;

(3) FIG. 2 is a diagram illustrating a second coil according to a second embodiment of the present invention;

(4) FIG. 3 is a diagram illustrating a third coil having primary and secondary windings partially wound together according to a third embodiment of the present invention;

(5) FIG. 4 is a diagram illustrating a fourth coil having interleaved primary and secondary windings according to a fourth embodiment of the present invention;

(6) FIGS. 5A-5C illustrate a force multiplying effect of a dual coil solenoid according to an exemplary embodiment of the invention;

(7) FIG. 6 is a diagram illustrating a fifth coil according to a fifth embodiment of the present invention;

(8) FIG. 7 illustrates an empty bobbin on which a coil is wound according to an embodiment of the present invention;

(9) FIG. 8 illustrates a standard 1200 winding coil;

(10) FIG. 9 illustrates a primary coil wound on a bobbin according to an embodiment of the present invention;

(11) FIG. 10 illustrates primary and secondary coils wound on a bobbin according to an embodiment of the present invention;

(12) FIG. 11 illustrates another embodiment of the present invention;

(13) FIGS. 12A-12C illustrate preferred dimensions of a dual coil solenoid according to an exemplary embodiment of the present invention; and

(14) FIG. 13 illustrates an electrical schematic of a GFCI device incorporating the dual coil solenoid device according to an embodiment of the present invention.

(15) Throughout the drawings, like reference numerals will be understood to refer to like features and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(16) A number of experiments were conducted with single winding and multiple winding solenoid coils, as will be described below. Standard GFCI coils have 1200 turns of 34 American Wire Gauge (AWG) wire. The resistance and wire size of four wire types were measured for comparison, and the results are in the following table:

(17) TABLE-US-00001 OD measured AWG OD mils with insulation Ohms/1000 33 7.1 8 211 34 6.3 7 266 35 5.6 6.5 335 36 5 5 423

(18) As can be appreciated from the above table, as AWG increases (that is, wire OD decreases) the electrical resistance of the wire increases. Next, a series of tests were conducted by modifying a standard solenoid coil having 1200 turns of 34 AWG wire, and modifying the coil by adding or removing turns of wire. As can be appreciated, a standard 1200 turn coil produced 2.4 lbs of force with a peak current of seven (7) amps, and 28 ohms. Producing a new coil of 1540 turns increased the resistance and reduced the current and force generated. Next, turns were gradually removed and the coil was retested with varying numbers of turns. As expected, the resistance decreased as the number of turns decreased, and the current increased. However, a maximum force of 3.15 lbs was produced with 750 turns, after which further reductions in the coil resulted in lower force.

(19) TABLE-US-00002 34 AWG amps force test # Coil turns ohms peak Lbs notes 1 1200 28 7 2.4 standard coil 2 1540 31 5.2 1.7 made with new wire 3 1400 27.75 5.8 1.85 removed wire 4 1300 25.65 6.5 2.1 heated 1.7 lbs 6.2 A 5 1200 22.05 7.2 2.1 heated 1.8 lbs 7 A 6 1100 19.56 8 1.8 heated 1.75 lbs 7 1000 17.33 >8 2.3 8 900 15.45 >8 2.45 9 850 14.75 >8 2.7 heated 2.5 lbs 10 800 12.9 >8 2.55 heated 2.3 11 750 11.98 >8 (11) 3.15 heated: 2.3 lbs@13.56 ohm, 62 C./ 2.7 lbs@12.7 ohm, 40 C. 12 725 11.31 2.8 limit reached

(20) Another test was conducted using an SCR to energize the coil, rather than directly controlling the relay. The results are below:

(21) TABLE-US-00003 New Testing conducted with SCR firing the coils in place of direct Relay control Standard production 34 AWG coils used and wire removed as tested. Coil test turns ohms amps peak force Lbs notes 1 1200 24 6.3 2.3 coil 0.348 OD 2 1100 21.3 7.28 2.5 3 1000 18.8 8.16 2.4 2.1 lbs@45 C. 4 900 16.51 2.5 2.1 lbs @ 45 C., 1.85 lbs @ 57 C. 5 800 14.29 2.5 coil 0.287 OD, 2.3 lbs @43 C., 2.1 lbs @ 58 C., 2 lbs @ 66 C. NO SCR failures 6 750 17.75 1.6 1.2 lbs @ 28 C.

(22) Next, a series of experiments were conducted by winding two or more separate coils together in various configurations. In each of the configurations described below, the coil wires are preferably wound around a bobbin helically and tightly, one layer at a time, with each layer wound outside the prior layer. Accordingly, the number of turns per layer of wire is related to the length of the bobbin divided by the diameter of the wire including insulation, and the volume of the resulting coil is substantially related to the diameter of wire and the total number of turns of wire in the coil.

(23) FIG. 1 illustrates a first coil configuration, in which a solenoid 100 was wound with a primary coil 102 wound together with a secondary coil 104. Accordingly, both the primary coil 102 and the secondary coil 104 have a start at the inside diameter (ID) of the solenoid, and have their ends at the outside diameter (OD) of the solenoid. The primary and secondary coils were wound together for 865 turns. The solenoid was tested by energizing the primary and secondary coils individually, and then by energizing both coils together. The results are shown in the table below:

(24) TABLE-US-00004 Coil wound with wire pair together to 865 turns New amps force test Coil turns ohms peak Lbs notes 1 865 coil 1 18.02 1.4 865 coil 2 18.03 1.4 both active 3.7 Resultant 32% gain in force

(25) As will be appreciated, the force of each coil energized separately was 1.4 lbs, while the force of the coils energized together was 3.7 lbs, or 32% higher than simply adding the force of each coil together.

(26) As shown in FIG. 2, a second solenoid 200 was wound with the primary coil 202 would first, for 750 turns, and the secondary coil 204 was then wound on top of the primary coil for 1333 turns. The solenoid 200 was tested with the primary and secondary coils energized separately, and then together. Next 133 turns were removed from the secondary coil 204 and the solenoid 200 was retested. Finally, 100 additional turns were removed from the secondary coil 204 and the solenoid 200 was retested again. The test results are shown below:

(27) TABLE-US-00005 Primary coil 750 turns, secondary on top = 1333 turns amps force Coil turns ohms peak Lbs notes 1 primary 750 13.66 11 2.4 2.sup.nd 1333 34.5 4.52 1.5 both active 4.7 Resultant 20% gain in force 2 removed 133 off 2.sup.nd primary 750 13.66 11 2.4 2.sup.nd 1200 29.6 4.88 1.2 both active 4.8 Resultant 33% gain in force 3 removed 100 off 2.sup.nd primary 750 13.66 11 2.4 heated 1.8 lbs @ 58 C. 2.sup.nd 1100 26.48 5.76 1.1 heated 0.8 lbs @ 55 C. both active 5.2 to 4.6 3.6 lbs @ 51 C., 3.3 lbs @ 58 C. Resultant 48% gain in force

(28) As will be appreciated, there was a performance gain when both coils were energized together, as compared to simply adding the force generated by each coil separately. The gain increased the closer the size of the primary coil was to the secondary coil. In the first trial the gain was 20%, in the second trial the gain was 33%, and in the third trial, when the secondary coil was closest in number of windings to the primary coil, the gain was 48% over simple addition of the forces generated by the primary and secondary windings separately.

(29) FIG. 3 illustrates a third solenoid 300 that was wound with a first portion of the primary coil 302 wound first for 350 turns. The secondary coil 304 was then wound together with the primary coil 302 (that is, the primary and secondary wires were wound at the same time, side-by-side) for 450 turns. Next, the primary coil 302 was ended, and the secondary coil 304 was wound on top of the foregoing portion for an additional 400 turns. Thus the primary winding 302 included a total of 800 turns and the secondary winding 304 included a total of 850 turns. The third coil 300 was tested with the primary and secondary windings energized separately, and then together. The results are shown below.

(30) TABLE-US-00006 Primary coil 800 turns, secondary 850 turns as shown, but wound ontop as one coil amps force new test Coil turns ohms peak Lbs notes 1 primary 800 14.65 10 1.9 1.2 lbs @ 60 C. 2.sup.nd 850 17.16 8.6 1.2 0.7 lbs @ 60 C. both active 4.4 3 lbs @ 43 C., 2.6 lbs @ 52 C., 2.4 lbs @ 60 C. Resultant 42% gain in force

(31) As will be appreciated, the force generated by the primary coil energized along was 1.9 lbs. The force generated by the secondary coil energized alone was 1.2 lbs. When both coils were energized together, however, the resultant force is significantly higher than the mere sum of the individual component forces generated by the coils. In other words, the coils generated a force of 4.4 lbs when energized together, which is a 42% gain over the sum of the forces generated by the coils when energized separately.

(32) FIG. 4 illustrates a fourth solenoid 400 that was wound with alternating layers of primary coil 402 and secondary coil 404. As illustrated, the primary coil 402 was first wound for 400 turns, then the secondary coil 404 was wound for 400 turns. Next, the primary winding 402 was wound again on top of the secondary winding. The two portions of primary winding were connected by a jumper 406. Similarly, the secondary coil 404 was wound on top of the foregoing portions for an additional 400 turns, with a jumper 408 connecting the two portions of the secondary coil 404. The solenoid was tested by energizing the primary and secondary coils separately, and then together. The results are shown below:

(33) TABLE-US-00007 Primary coil 800 turns, secondary 800 turns as shown, but wound on top as one coil amps force new test Coil turns ohms peak Lbs notes 1 primary 800 17.77 9.76 1.6 1.23bs @ 66 C. 2.sup.nd 760 15.22 8.36 1.2 1.0 lbs @ 66 C. both active 4.2 3.2 lbs @ 66 C. Resultant 50% gain in force

(34) As can be seen, the resulting force gain for this configuration was 50%, better than the previous embodiments. However, this configuration proved more difficult to wind than previous embodiments, and the OD was larger than desired.

(35) By operating two separate coils simultaneously, the magnetic field is focused closer to the central axis of the plane of the solenoid plunger, thus yielding higher forces than the added forces of the field generated by either coil alone. The focusing of the magnetic field onto the axis of a solenoid plunger will now be described in further detail in connection with FIGS. 5A-5C. FIGS. 5A-5C illustrate a solenoid 500 having a primary coil 502 and a secondary coil 504 that is preferably wound outside the primary coil 502. When one or both of the coils 502, 504 are energized, and magnetic flux is generated that imparts a force on a plunger 506 located in the core of the solenoid 500.

(36) FIG. 5A illustrates the solenoid 500 with the primary coil 502 energized and the secondary coil 504 not energized. The primary coil 502 generates a magnetic field having a particular flux or field density in the core that imparts a first force on the plunger 506. Preferably, the first force generated by the primary coil 502 is preferably greater than a threshold force required to move a latch device of a ground fault circuit interrupter. In other words, the first force generated by the primary coil 502 when energized independently should be enough to trip a GFCI device in which the solenoid 500 is installed.

(37) FIG. 5B illustrates the solenoid 500 with the secondary coil 504 energized and the primary coil 502 not energized. The secondary coil 504 generates a magnetic field having a particular flux or field density in the core of the solenoid that imparts a second force on the plunger 506. The magnetic field generated by the secondary coil 504 is generally weaker per unit winding and current since the wires of the secondary coil 504 are wound outside the primary coil 502 and therefore are farther away from the core of the solenoid 500 and the plunger 506. It is desirable that the first force generated by the primary coil 502 and the second force generated by the secondary coil 504 be closely matched, such that the first force generated by the primary coil 502 and the second force generated by the secondary coil 504 are each greater than the threshold force required to trip a GFCI device, as described above. Accordingly, the wire gauge, number of windings, and other parameters of the primary and secondary coils 502, 504 are preferably selected to closely match the forces generated by the coils when they are independently energized, such that the forces generated by each coil are separately greater than a threshold force required to trip a GFCI device. The parameters of the coils are also preferably selected so that the solenoid, including both primary and secondary coils 502, 504 has an OD smaller than a predetermined size requirement.

(38) FIG. 5C illustrates the solenoid 500 with the primary coil 502 and the secondary coil 504 energized together. As illustrated the magnetic field generated by the secondary coil 504 essentially squeezes the magnetic field generated by the primary coil 502 within the core of the solenoid. As a result the magnetic field density is increased along the axis of the plunger 506, compared to what would be expected by simply adding the magnetic fields generated by the primary coil 502 and the secondary coil 504 energized independently. In the example illustrated in FIGS. 5A-5C, the primary coil 502 generates a force of 1.6 lbs on the plunger 506 when energized independently. The secondary coil 504 generates a force of 1.5 lbs on the plunger 506 when energized independently. However, advantageously, the force generated when the primary and secondary coils 502, 504 are energized together is 4.4 lbs, which represents of 42% gain over a simple sum of the forces generated by the coils separately (3.1 lbs).

(39) The embodiment described above has several important advantages over conventional solenoids used in GFCI devices. First, having two separate coils capable of independent energization provides an important failsafe backup operation. Accordingly, even if one of the coils becomes short circuited or open circuited, the remaining coil can generate enough force to trip the GFCI device. Second, when both coils are operating together, the combined force is amplified such that a smaller solenoid can produce more force. Thus, a solenoid according to embodiments of the present invention can fit into smaller spaces while producing greater force, and having greater tolerance for operating environments such as temperature ranges. Embodiments of the present invention enable the design of smaller GFCI devices, and/or permit the design of GFCI devices that include additional components without increasing the overall size of the GFCI housing.

(40) FIG. 6 illustrates a fifth coil 600 that was wound and tested. The fifth coil 600 was substantially similar to the first coil 200 illustrated in FIG. 2, except that different gauge wires were used for the primary and secondary windings. In the coil 600 shown in FIG. 6, the primary coil was formed with 34 AWG wire, and the secondary coil was formed with 33 AWG wire. The primary coil was formed by removing 400 turns from a standard 1200 turn solenoid. The secondary coil 504 was wound for 1000 turns. The results are shown in the following table:

(41) TABLE-US-00008 amps force Coil turns ohms peak Lbs notes Primary 800 14.53 10.5 2.5 34 AWG Secondary 21.2 7.28 1.2 33 AWG 1000 both active 5 Resultant 35% gain in force

(42) As can be appreciated, the resulting force gain was 35% greater than would be expected by simply adding the forces of the individual windings together.

(43) Next, 50 turns were removed from the secondary, and the solenoid was retested, with the following results:

(44) TABLE-US-00009 amps force Coil turns ohms peak Lbs notes Primary 800 14.53 10.5 2.5 34 AWG Secondary 19.65 7.8 1.4 33 AWG 950 Both active 5.5 Note highest yield single pulse Resultant 42% gain in force

(45) As can be appreciated from the above table, the force generated by the secondary winding alone was 1.4 lbs, which is greater than the 1.2 lbs in the previous test when the secondary winding had 1000 turns. Also the force of the combined windings was 5.5 lbs, a 42% gain over simply adding the forces of the individual windings together.

(46) Next, another 50 turns were removed from the secondary, and the solenoid was tested again, with the following results:

(47) TABLE-US-00010 amps force Coil turns ohms peak Lbs notes Primary 800 14.53 10.5 2.5 34 AWG Secondary 18.2 8.68 1.3 33 AWG 900 Both active 5.3 Resultant 40% gain in force

(48) Accordingly, as can be appreciated from the above table, this configuration did not perform as well as the prior configuration, either in total force produced by the combined windings (5.3 lbs) or in percent gain over the addition of forced produced by the individual windings energized separately (40%). Of the three configurations tested, the 950 turn configuration proved optimal.

(49) FIG. 7 illustrates a typical empty plastic bobbin 700 of a solenoid, on which wire windings are wound. The typical dimensions, as shown, are 0.7075 long, ID 0.190, and OD 0.4060. FIG. 8 illustrates the plastic bobbin 700 with a standard 1200 turn winding 702 wound on the bobbin 700.

(50) FIGS. 9 and 10 illustrate the construction of a solenoid according to the embodiment described in connection with FIG. 6, with a primary winding 602 of 800 turns of 34 AWG wire and a secondary winding 604 of 950 turns of 33 AWG wire. As illustrated in FIG. 9, the primary winding ends in an incomplete row, and accordingly, the OD of the primary winding is 0.2985 at one end of the bobbin, and 0.2960 at the other end of the bobbin. As shown in FIG. 10 the OD of the solenoid is 0.4725. This OD was undesirably large, and the force generated was more than needed.

(51) Another test was conducted using a construction substantially similar to the fifth coil 600 shown in FIG. 6, but with smaller diameter 35 AWG wire used for the primary winding, rather than 34 AWG, and 33 AWG wire used for the secondary winding. This resulted in the individual forces imparted by the separate windings being better matched, and a reduced OD. The results are shown in the table below:

(52) TABLE-US-00011 amps force Coil turns ohms peak Lbs notes Primary 800 17.58 8.68 1.6 35 AWG Secondary 19.06 8.08 1.35 33 AWG 950 Both active 4.2 3.3 Lbs @ 67 C., 3.1 Lbs @ 72 C. Resultant 45% gain in force

(53) As can be appreciated from the above table, the above configuration resulted in a 45% gain in force over the simple addition of forces generated by the individual windings separately.

(54) When wire was wound on the bobbin or spool in single tightly wound layers, it was found that the following number of turns were wound in one complete row:

(55) 33 AWG=87 turns

(56) 34 AWG=96 turns

(57) 35 AWG=118 turns

(58) FIG. 11 illustrates a preferred embodiment of a coil 1100 that was wound with the primary coil 1102 being made of 35 AWG wire. Preferably, the coil is wound such that the outer layer of the coil is completed, making it easier to pull the primary winding ending over the secondary coil to fix to the termination pin. This may be accomplished by selecting the number of turns such that the tightly wound coil ends with a complete layer, or by loosely winding the last few turns to span the outer layer of the coil. The secondary coil 1104 was made of 33 AWG wire and 950 turns. The primary coil 1102 has a resistance of 16.58 ohms and when energized resulted in a current of 8.84 to 8.92 amps and a force of 1.5-1.6 lbs at an operating temperature of 27 C. The secondary coil 1104 has a resistance of 18.4 ohms, and when energized resulted in a current of 7.92 to 8.16 amps and a force of 1.35-1.5 lbs at an operating temperature of 26 C. The force generated on the plunger when both coils are operated together is 4.4 lbs at 26 C. (or a 42%-54% gain). The plunger OD is preferably 0.125, and the solenoid OD is preferably 0.450.

(59) An exemplary embodiment of a solenoid constructed according to an embodiment of the invention is illustrated in FIGS. 12A-12C. The primary coil 1201 is wound onto a bobbin having a diameter of 0.190 inches and a length of 0.709 inches. Accordingly, the primary coil has an inside diameter (ID) of 0.190 inches. The primary coil is preferably formed of 35 AWG wire and is wound for 800 turns on the bobbin, in smooth substantially complete layers. Such a primary coil will have an outside diameter (OD) of 0.290 inches, and a resistance of 18 ohms +/15%, and is illustrated in FIG. 12A. The secondary coil 1202 is wound outside the primary coil 1201 and has an ID the same as the OD of the primary coil 1201, that is 0.290 inches. The secondary coil is preferably formed of 33 AWG wire and is wound for 950 turns on the bobbin. Such a secondary coil will have an outside diameter (OD) less than 0.445 inches, and typically 0.440 inches. The resistance of the secondary coil is 16.9 ohms +/15%. The secondary coil is illustrated in FIG. 12B, and an end view of both coils is illustrated in FIG. 12C. The beginning and end of each coil are available for connection to other circuit components of a device which incorporates and utilizes the dual coil solenoid, such as a GFCI, as may be needed.

(60) FIG. 13 is circuit schematic of a GFCI device 1300 utilizing a dual coil solenoid according to another embodiment of the present invention. In operation, sense coil 1301 senses a net current between the main hot and neutral conductors 1302 and 1303, and provides a signal to sense controller 1304. When sense controller 1304 senses a signal indicative of a differential current exceeding a predetermined threshold on the hot and neutral conductors 1302 and 1301, the sense controller provides a fault signal (SCR_OUT) to the gate of SCR 1305. The SCR 1305 turns on when the fault signal is applied to the gate of SCR 1305, and in turn provides a gate signal to SCRs 1306 and 1307. A first current path is formed between a line hot terminal 1308 of the GFCI device 1300 and ground, passing first through secondary coil 1202, fuse 1309, diode 1310 and SCR 1306. A second current path is formed between the line hot terminal 1308 and ground, passing first through primary coil 1201, fuse 1311, diode 1312, and SCR 1307.

(61) As will be appreciated, under normal conditions, when a fault is sensed, both SCRs 1306 and 1307 will turn on, and both the primary and secondary coils 1201 and 1202 will be energized, imparting a combined force on a plunger to trip open a set of contacts 1313 to remove input power from load and receptacle (face) contacts. Preferably, a device such as an opto-isolator 1314 provides a confirming signal to a monitoring controller 1315 to confirm proper operation of the trip circuit and opening of the contacts 1313. If contacts 1313 do not open in response to a fault signal, monitoring controller 1315 preferably enters an end-of-life state.

(62) As will further be appreciated, in the event that either the primary coil 1201 or the secondary coil 1202 of the solenoid becomes damaged, such as by short circuit or open circuit in the coil wire, the remaining coil is advantageously fully capable of generating enough force to trip the device and safely open the contacts 1313. Further, if either of the SCRs 1306 and 1307 fail, the remaining SCR is advantageously capable of energizing its corresponding solenoid coil 1201 or 1202 to trip the device and safely open the contacts 1313.