MXPA95003980A - Compact set of coil for transient voltage protection - Google Patents

Abstract

The present invention relates to a compact coil assembly for protecting electrical components against shock waves of transient voltage, the assembly comprising: a coil having a cylindrical core with two ends; first and second flanges, each mounted perpendicularly in and extending outward from one end, the first and second flanges each having a top surface opposite the end, a terminal pin erect perpendicularly on the upper surface of the first flange, the first flange having parallel external and internal walls that they define a channel therebetween, the inner wall having a groove therethrough, the groove being open at one end to the upper surface of the first flange and extending down to the core, the groove being placed on the upper surface of the first flange opposite the terminal pin, the channel extending from the end pin l through the end of the groove near the core, the width of the channel and the groove adapted to guide a winding wire to its cross

Description

COMPACT COIL SET FOR PROTECTION AGAINST TRANSIENT VOLTAGE Field of the Invention The present invention relates to a coil assembly and, more particularly, to a compact solenoid coil that protects ground fault circuits against transient voltage shock waves. BACKGROUND OF THE INVENTION Electric systems in residential, commercial and industrial applications usually include a board to receive electric power from a source of electricity. The energy is then routed through overcurrent protection devices to designated branch circuits that supply one or more loads. These overcurrent devices are typically circuit breakers such as circuit breakers and fuses that are designed to interrupt electrical power if the limits of the conductors supplying the loads are exceeded. Interrupting the circuit reduces the risk of injury or the potential for property damage resulting from a fire. Circuit breakers are a preferred type of circuit breaker because the reset mechanism allows re-use. Typically, the circuit breakers interrupt an electrical circuit due to a trip condition such as a current overload or a ground fault. The current overload condition is the result of a situation in which the current exceeds the continuous rated capacity of the circuit breaker by a time interval determined by the tripping current. The ground fault trip condition is created by an imbalance of currents flowing between a line conductor and a neutral conductor such as a grounded conductor, a person causing a "ground-to-ground" path, or a failure to ground arc to ground An example of a ground fault interrupter is a fast-acting circuit breaker that disconnects equipment from the power line when some current returns to the source through a ground path. the current is supplied and returned inside the power conductors, but if a fault occurs and some current is filtered to ground, then the circuit breaker - Ground fault ~ (GFCI) will detect the difference in current in the power conductors. If the fault level exceeds the trigger level of the GFCI, then the circuit will be disconnected. The trigger level for personnel protection is usually in the range of around 4 to 6 mA. The trigger level for equipment protection is usually around 30 mA. GFCI and other equipment often use solenoid coils for protection against electrical transients, particularly when electrical voltage clamps such as metal oxide varistors (OVs), Zener diodes, or spark gap are used in the circuit. The coil must absorb the transient shock wave of both voltage and electrical power in a short period of time, typically of the order of microseconds. If the transient voltage interrupts the coil, it could endanger other components of the circuit. The ability of the coil to withstand voltages depends on the insulation between the windings of the coil. In the conventional manufacture of a winding in a coil, a guide wire extends downwards along the side of the coil to the surface of the core of the coil. Tape is usually placed on this guide wire as the reel is being wound. The guide wire is usually the area of the initial voltage interruption, however, because it extends from the top to the bottom of the layered side of the winding. There are additional complications to improve the ability of the coil to withstand a shock wave of transient voltage. To achieve a higher nominal voltage rating, the distance between the winding layers must be increased or a barrier must be inserted. However, as the coil carrying devices become smaller and smaller, there is a need to achieve these protective features in a more compact design.

In view of the increasing size restrictions for coils and their devices, there is a need for a coil assembly with the ability to absorb transient voltage shock waves in a more compact design. There is another need for a coil manufactured at low cost that can more effectively insulate the guide wire from the rest of the coil winding to improve its ability to absorb transient voltage shock waves. SUMMARY OF THE INVENTION In accordance with the present invention, a compact coil assembly is provided for protecting electrical components against transient voltage shock waves. The assembly includes a coil having a cylindrical core with two ends. First and second flanges are mounted perpendicularly to each other and extend outward from one end. The first and second flanges each have a top surface opposite the end. A terminal pin is erect perpendicularly on the upper surface of the first flange. The first tab has parallel external and internal walls that define a channel between them. The inner wall has a groove through it. The slot is open at one end to the upper surface of the first flange and extends down to the core. The groove is placed on the upper surface of the first flange opposite the terminal pin. The channel extends from the terminal pin through to the end of the slot near the core. The width of the channel and the groove is adapted to guide a winding wire therethrough. The present invention also provides a ground fault circuit interrupter that includes a molded plastic housing and an electronic signal processor. The processor determines ground fault conditions within a protected circuit and provides an output signal to operate a pair of contacts to interrupt the flow of current through the circuit. The switch also includes a coil assembly of the type described above with first and second windings around the core of the coil. The present invention also provides a ground fault circuit protected against transient voltage shock waves. The circuit includes means for detecting a current imbalance between a line and a neutral. An electronic signal processor determines ground fault conditions within a protected circuit and provides an output signal adapted to operate a pair of contacts to interrupt the flow of current through the circuit. The coil assembly is electrically connected to the protected circuit and to the electronic signal processor to absorb voltage shock waves. Accordingly, an object of the invention is to provide a coil assembly that uses multiple barriers to improve the coil's ability to absorb voltage shock waves. Another object of the invention is to provide a coil assembly that increases the ability to absorb shock waves of voltage in the same volume. A further object of the invention is to provide a GFCI that is protected from electrical transients. Still another object of the present invention is to provide a coil assembly that protects an associated electrical device from harmful electrical transients. Other and additional advantages, embodiments, variations and the like will be apparent to those skilled in the art from the present description, taken with the accompanying drawings and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which comprise a portion of this disclosure: Figure 1 is a perspective view of an embodiment of the present invention illustrating a compact coil assembly; Figure 2 is a cross-sectional view taken along lines 2-2 of Figure 1; Figure 3 is a cross-sectional view taken through the core of a coil similar to that of Figure 2, illustrating an alternating coil assembly; Figure 4 is a cross-sectional view taken along lines 4-4 of Figure 1; Figure 5 is a schematic diagram of a circuit used in accordance with the present invention to protect a ground fault circuit against electrical transients with a coil assembly; and Figure 6 is a schematic diagram of another circuit embodiment used in accordance with the present invention to protect a ground fault circuit against electrical transients with a coil assembly. Detailed Description A coil assembly 10 is sketched in Figures 1, 2 and 4, and includes a coil 12 having a generally cylindrical core 14 with two ends 16 and 18. A first flange 20 and a second flange 22 are formed perpendicular to each other. integrally with respective ends 16, 18. The first and second flanges 20, 22 extend outwardly from the core 14 and are adapted to retain a coil winding therebetween. The first flange 20 includes a channel 24 formed by an outer wall 26 and an internal wall 28. The channel 24 extends from a first terminal pin 30 at one end to a slot 32 at the other end of the channel 24. The first pin of terminal 30 is mounted on an upper surface 34 of the first flange 20. The slot 32 is formed through the inner wall 28 from the upper surface 34 of the first flange to the core 14. The width of the channel 24 and the slot 32 is sufficient to accommodate a guide end 36 of a first winding 38. The guide end 36 of the winding is electrically and mechanically connected to the first terminal pin 30. The guide end 36 of the winding extends immediately along the channel 24 below the winding. the surface 34 of the flange. ____ A floor portion 40 of the channel is beveled downward toward the core 14 to guide the guide end of the winding to position on the surface 42 of the core. The coil 12 preferably includes an electrically insulating barrier 44 formed integrally at one end with the surface 42 of the core. The barrier 44 has an upper surface 46 erected perpendicularly from the core 14. The barrier 44 is positioned approximately midway between the ends 16 and 18 of the core. The first winding 38 extends in overlapping layers from the inner wall 28 of the flange on one side, to one side 48 of the barrier 44 on the other. The layers of the first winding 38 accumulate on themselves to extend close to the upper surface 46 of the barrier. Once the first winding 38 is completed between the inner wall 28 and the barrier 44, the winding wire 50 extends over the upper end 46 of the barrier through a slit 52 which retains the winding wire 50. in position below the upper surface 46 of the barrier. The winding wire then extends downward along another side 54 of the barrier to the surface 42 of the core. In a manner similar to that described above, a second winding 56 is formed in overlapping layers between the barrier 44 and the flange 22. The second winding 56 has a terminating end 58 extending from the upper layer of the second winding 56 to a second terminal pin 60 and electrically and mechanically connected thereto. The flange 22 has an upper surface 62 with a displacement 64 for retaining the terminating end 58 of the second winding in stop relation. Mounting points similar to 66 are also attached to the upper surfaces of the flanges 20, 22. An alternate embodiment of a coil assembly 310 contemplated by the present invention for the arrangement of the first and second windings 338 and 356 is illustrated in Figure 3. As described above, a guide end 336 of the coil 356 is guided down a channel 324 to the surface 342 of the core. The first winding 338 extends in fully overlapping layers through the area between the first and second flanges 320, 322. Once the first winding 338 is completed, it is covered by a layer of electrically insulating tape 344 to form a second type of barrier. A winding wire 350 continues upwardly along the inner surface of an inner wall 328 or flange 322 and initiates the second winding 356. Similarly, the second winding 356 extends in overlapping layers near the upper surfaces 334. , 362 of the respective tabs 320, 322. A terminating terminal 358 is connected to a second terminal pin 360, as described above. A preferred embodiment of coil assembly 10 includes approximately 1,000 turns of 37 gauge magnetic wire having a heavy duty insulation such as NEMA type MW-75. The diameter of the core is around 0.186 in. The first and second terminal pins extend about 0.1 in. On the surface of the eyelashes. The overall height of the coil is around 0.5 in. The coil is made of an electrically insulating material such as plastic. Preferably, the plastic used is a nylon or a glass-filled nylon compound. A suitable manufacturing technique for making the coil is injection molding. Samples of the coil assembly of the invention were tested to comply with the standard of Underwriters Laboratories (UL) 943, class A, for personnel protection and 1056, class 1, for equipment protection. In one of the tests, the samples were subjected to a shock wave of 6,600 volts through the power connections in accordance with IEEE 587. No damage was observed to the arc-forming device or display during the test with a current of no more than the average of 50 units of no arc formation plus 10 amps. Generally, the coil assembly of the invention is available for the protection of various circuits and electrical devices against damaging voltage pulses. One of the many applications of the present invention is its use with ground fault interrupters. Turning now to Figure 5, a ground fault circuit 100 is illustrated. A service line 102 and a neutral line 104 are connected to a load 106. A current transformer 108 is provided to detect any imbalance in the current that flows through the line 102 and the neutral 104. The current transformer 108 outputs a signal to a GFCI 110 control. The GFCI 110 control is of a conventional type, suitable for mounting with or connection to a circuit breaker electronic trigger circuit, board or similar (not shown). A coil assembly 112, as described above, is connected at one end to line 102 and at the other end to a rectifier 114. Rectifier 114 is also connected to a circuit ground 116 and returns to neutral 104.

The GFCI control 110 is connected to the rectifier 114 through a resistor 118 that provides voltage drop for the power source. The coil assembly 112 acts as an impedance and its ability to absorb voltage shock waves protects the GFCI control 110 against potential damage. The GFCI control 110 is additionally connected to a gate 120 of a silicon controlled rectifier (SCR) 122. The SCR 122 has an anode 124 which is connected to the rectifier 114 and a cathode 126 which is connected to the circuit ground. Other rectifying means are suitable for use with the present invention. A preferred ground fault circuit 130 is illustrated in Figure 6. A coil assembly 132, as described above, is connected to a service line 134 and a rectifier 136. The rectifier 136 has a direct negative 138 that it is connected to ground and a DC positive 140 that is connected to a MOV 142 for over-voltage protection. The invention contemplates using other means for overvoltage protection, such as voltage clamp devices such as Zener diodes. The coil assembly 132 is connected to a GFCI control 144 through a stabilizing capacitor 146 provided to filter the line voltage and reduce the zero voltage for a complete wave. Resistors 148 and 150 are provided to drop the energy towards the GFCI 144 control.

The GFCI control 144 includes an amplifier 152 which is connected to a detector transformer 154 through the capacitors 156 and 158 and the resistor 160. The detector transformer 154 detects an imbalance in the current between the line 134 and neutral 162 and generates a signal directed to the control of GFCI 144. A neutral ground transformer 164 is also provided to prevent operation of the GFCI 144 control if the neutral 162 is not properly connected. The output of the amplifier 152 through a capacitor 166 to the grounded neutral transformer 164 establishes an oscillation to simulate a ground fault if there is a short from the neutral ground transformer 164 to the detector transformer 154. The output of the amplifier 152 is also connected through of the resistors 168 and 170 to the inverted gate of the amplifier 152 and the transformers 164 and 154. The amplifier 152 is connected to a circuit ground at 172 and to a SCR 174 through a second stabilizing capacitor 176. The SCR 174 it is connected to the rectifier 136 and also to a circuit ground. The amplifier 152 also connects a non-inverted gate to the transformers 154 and 162 through the capacitor 178. The rectifier 136 is also connected to a test input 180. To simulate a ground fault, a current from the test input 180 passes , through the resistors 182 and 184, to the detector transformer 154, which detects any artificially created imbalance to test the GFCI control 144. Two examples of the component values used for the circuit of FIG. 6 are provided . These examples are for illustrative purposes only and are not intended to be limiting. A first example is to provide protection for personnel from a failure of more than about 5 mA. For a line of 120 volts, the value of the MOV is 150 volts. The capacitors 146 and 176 have a capacitance of 2,200 pF at 200 volts. The capacitors 158 and 178 have a value of 1,000 pF. The capacitor 156 has a value of 6.8 μF. Capacitor 166 has a capacitance of 1,500 pF. Resistors 182 and 184 have a value of 7.5 k Ohms at 1/2 watt. Resistors 168 and 170 have a value of 787 k Ohms and 62 k Ohmsrespectively, to 1/8 watt. A second example is to provide protection for equipment from a fault of more than about 30 mA. For a line of 120 volts, the value of the MOV is 150 volts. The capacitor 146 has a capacitance of 2,200 pF at 200 volts. The capacitors 158 and 178 have a value of 1,000 pF. The capacitors 156 and 176 have a value of 6.8 μF. The capacitor 166 is not used in the circuit. Resistors 148 and 150 have a value of 15 k Ohms at 0.5 watts. Resistors 182 and 184 have a value of 1.0 k Ohm to 1/2 watt. Resistors 168 and 170 have a value of 133 and 12 k Ohms, respectively, at 1/8 watt. The ground neutral transformer 164 is not used in the circuit. The methodology and coil assembly apparatus described above can be advantageously used for protection against voltage shock waves of all types of GFCIs. Three types of GFCIs are commonly available. The first or type of separate housing is available for circuits of 120 volts, two cables and 120/240 volts, three cables, up to 30 amps. The second type combines a circuit breaker of 15, 20, 25 or 30 amps and a GFCI in the same plastic housing. It is installed in place of an ordinary circuit breaker on a board and is usually available in 120 volt, two wire or 120/240 volt types, three wires, which can also be used to protect a 240 volt, two wire circuit. The second type provides protection against ground faults and overloads for all the outlets in the circuit. A third type that has a receptacle and a GFCI in the same housing provides only protection against ground fault to the equipment connected in that receptacle. There are GFCI cross-feed types that provide protection for connected equipment in other ordinary receptacles installed downstream on the same circuit. Examples of ground fault equipment are available • - commercially from Square D Company under the catalog designations Ground-Censor (brand), Homeline (registered trademark), QO (registered trademark), Trilliant (registered trademark) and Micrologic (registered trademark) for ground fault modules. This ground fault equipment is suitable for protection of main, feeder and motor circuits in electrical distribution systems. It is also capable of being used as earth fault relays and ground fault detection devices. Although particular embodiments and applications of the present invention have been illustrated and described, it should be understood that the invention is not limited to the construction and precise compositions disclosed herein and may be made by those skilled in the art various changes. , modifications and variations in the arrangement, operation and details of construction of the invention disclosed herein, without departing from the spirit and scope of the invention, as defined in the appended claims.

Claims (11)

1. . CLAIMS What is claimed is: 1. A compact coil assembly for protecting electrical components against transient voltage shock waves, the assembly comprising: a coil having a cylindrical core with two ends; first and second flanges, each mounted perpendicularly on and extending outwardly from one end, the first and second flanges each having a top surface opposite the end; an erect terminal pin perpendicularly on the upper surface of the first flange; the first flange having parallel external and internal walls defining a channel therebetween, the inner wall having a groove therethrough, the groove being open at one end to the upper surface of the first flange and extending down to the core, the groove being positioned on the upper surface of the first flange opposite the terminal pin, the channel extending from the terminal pin through to the end of the groove near the core, the width of the channel and the groove adapted to guide a winding wire to its through. The assembly of claim 1, wherein the coil further includes a barrier connected to the core and erected perpendicularly therefrom, the barrier having an upper surface opposite the core and being positioned about halfway between the first and second flanges and second. The assembly of claim 2, wherein the upper surface of the barrier comprises a slit extending across the width of the barrier, the width of the slit adapted to retain a winding wire therethrough. 4. The assembly of claim 1, wherein the assembly further includes first and second windings around the core of the coil. The assembly of claim 4, wherein the coil further comprises a barrier connected to the core and erected perpendicularly therefrom, the barrier having an upper surface opposite the core and being positioned about half the way between the first and second flanges, the upper surface of the barrier having a slit extending across the width of the barrier, the first winding positioned between the first flange and the barrier, the first winding connected to the second winding by means of a winding wire extending through the slit in the upper surface of the barrier, the second winding placed between the barrier and the second flange. The assembly of claim 4, wherein the first winding is positioned between the first and second flanges about the core, the assembly further comprising an electrically insulating tape barrier wrapped on the first winding, the second winding placed on the first winding and the tape barrier between the first and second tabs. The assembly of claim 1, wherein the upper surface of the second flange comprises a second terminal pin erected perpendicular thereto, the upper surface having a displacement near the second terminal pin, the displacement adapted to retain a winding wire at. 8. A ground fault circuit interrupter to protect a circuit, the switch comprising: a molded plastic housing; an electronic signal processor for determining ground fault conditions within a protected circuit and for providing an output signal for operating a pair of contacts to interrupt the flow of current through the circuit; a coil assembly positioned within the housing and electrically connected to the protected circuit and to the electronic signal processor to absorb voltage pulses; the coil assembly including a coil having a cylindrical core with two ends; first and second flanges, each mounted perpendicularly on and extending outwardly from one end, the first and second flanges each having a top surface opposite the end; an erect terminal pin perpendicularly on the upper surface of the first flange; the first flange having parallel external and internal walls defining a channel therebetween, the inner wall having a groove therethrough, the groove being open at one end to the upper surface of the first flange and extending down to the core, the groove being positioned on the upper surface of the first flange opposite the terminal pin, the channel extending from the terminal pin through the end of the groove near the core, the width of the channel and the groove adapted to guide a winding wire to its through; and first and second windings around the core of the coil. The switch of claim 8, wherein the coil further comprises a barrier connected to the core and erected perpendicularly therefrom, the barrier having an upper surface opposite the core and being positioned about halfway between the first and second flanges, the upper surface of the barrier having a slit extending across the width of the barrier, the first winding positioned between the first flange and the barrier, the first winding connected to the second winding by a winding wire extending through of the slit in the upper surface of the barrier, the second winding placed between the barrier and the second flange. The switch of claim 8, wherein the first winding is positioned between the first and second flanges about the core, the assembly further comprising an electrically insulating tape barrier that wraps over the first winding, the second winding placed over the first winding and the tape barrier between the first and second tabs. The switch of claim 8, wherein the upper surface of the second flange comprises a second terminal pin erect perpendicularly therefrom, the upper surface having a displacement near the second terminal pin, the displacement adapted to retain a winding wire at.