WO2000026679A9

WO2000026679A9 - Low cost electrical circuit breaker locater with passive transmitter and receiver

Info

Publication number: WO2000026679A9
Application number: PCT/US1999/025775
Authority: WO
Inventors: Joachim Wottrich
Original assignee: Unique Technologies Llc; Joachim Wottrich
Priority date: 1998-11-03
Filing date: 1999-11-02
Publication date: 2002-08-22
Also published as: EP1127279A4; JP2002529888A; WO2000026679A1; EP1127279A1; HK1039980A1; AU1711500A

Abstract

A system for locating a circuit interrupter, e.g. a circuit breaker, associated with a selected branch circuit (40-45) from amongst a plurality of circuit interrupting devices, CB1-CB6. The system includes a receiver (300) and a passive transmitter (100). The passive transmitter (100) when electrically connected to a branch circuit creates a current spike signal on that circuit at a predetermined frequency. This current spike signal has a sufficiently short spike duration so as to only generate a weak electromagnetic field about the circuit wire, which in turn, substantially minimizes the development of a sympathetic signal on other branch circuits adjacent to the selected branch circuit. Thus, the true current spike signal is easily distinguishable from any sympathetic signals. Accordingly, the receiver (300) can be broadly tuned about the predetermined frequency of the current spike signal and drives a user-perceivable signaling device upon sensing the current spike signal. A method for locating a circuit interrupter is also disclosed.

Description

LOW COST ELECTRICAL CIRCUIT BREAKER LOCATOR WITH PASSIVE

TRANSMITTER AND RECEIVER

Background of the Disclosure

1. Field of the Invention The present invention relates in general to electrical power line test equipment devices and, in particular, to a system for distinguishing the circuit-interrupting device (circuit breaker or fuse) associated with a particular electrical line from a plurality of circuit interrupting devices.

2. Background Art

When electrical work needs to be performed on an electrical system in a building or facility, it is usually necessary to trace and identify which circuit interrupter device (i.e., circuit breaker or fuse) is supplying power to a specific AC power branch circuit.

Manual identification of the fuse or circuit breaker can be accomplished by removing each fuse or opening each circuit breaker, thereby disrupting the power flow through the circuit. Each test point must subsequently be examined to determine whether the power to the test point has been disconnected. This method is not only time consuming, but also may not be feasible in situations where it would be hazardous to interrupt the power flow to certain branch circuit outlets, i.e., in a hospital or in environments where there are computers in use without backup power.

There are a number of prior art circuit testers for identifying the circuit-interrupting device that is supplying power to a specific outlet receptacle. Because most buildings and homes did not incorporate any circuit identification means into their respective electrical power panels, the majority of the prior art consists of a signal generating unit (i.e. transmitter) and a separate receiver unit that use a "pick-up" coil to sense the magnetic field from the signal generated by the transmitter. Some prior are circuit testers plug a passive signal device into a test outlet in order to draw an identification signal current over the selected circuit branch wiring from the electrical circuit interrupter panel or fuse box. However, where the identification signal current was of very low amplitude in comparison to the 60 Hz AC power line signal, this approach requires a very sensitive receiver unit, which is likely to be complex and expensive.

Accordingly, it is an object of the present invention to provide a circuit tester that provides an identification signal that is easily detectable by an adequately sensitive receiver, and is simple to implement and inexpensive to produce .

In one prior art circuit tester disclosed in Knopka, U.S. Patent No. 4,906,938, a simple passive transmitter draws a high amplitude signal from the electrical circuit interrupter panel through the selected branch circuit, which creates a magnetic field that readily couples to adjacent AC wire lines, resulting in sympathetic (false) identification signals on those adjacent wires. In this prior art system to improve differentiation between the actual and sympathetic signals (before general use) , the operator has to calibrate the sensitivity of the receiver. Such calibration is accomplished by either manually adjusting the receiver sensitivity or observing signal strength sensitivity via a meter. These manual compensation approaches can be quite difficult especially for novice users. Furthermore, since signal strength is a function of constantly altering line impedance and capacitance, these prior art receivers may require continual adjustment. Accordingly, it is another object of the present invention to provide a circuit tester that provides more reliable identification of a selected circuit branch while making it easier and less time consuming for the user to operate by eliminating the need for manual calibration and the associated potential for user error.

These and other objects of the invention will be apparent to those of ordinary skill in the art having the present drawings, specification and claims before them. Summary of the Invention

The present invention includes, in part, a system for locating a circuit interrupter associated with a selected branch circuit from amongst a plurality of circuit interrupting devices. The system comprises a passive transmitter and a receiver. The passive transmitter is operably connectable to a selected branch circuit such that upon establishment of such connection the passive transmitter causes a current spike signal of predetermined frequency to be drawn through the circuit interrupter associated with the selected branch circuit. Current flow in a wire always induces an electromagnetic field about the wire. As a consequence, a sympathetic current will flow in any wires that lie within the magnetic field surrounding the first wire. In the present invention, because the current spike signal produced by passive transmitter is of significantly short duration only a weak electromagnetic field is generated which cannot induce a full strength sympathetic signal in adjoining wires. Consequently, the difference in signal strength of the current spike signal on particular branch circuit produced by passive transmitter and any sympathetic signals developed on adjacent branch circuits.

The receiver of the present system is broadly tuned about the predetermined frequency of the current spike signal created on selected branch circuit and drives a user- perceivable signaling device upon sensing the predetermined frequency of the current spike signal .

In one embodiment, the passive transmitter comprises a RC circuit, a voltage-controlled switch, a Silicon Controlled Rectifier (SCR) , and a second capacitor. The RC circuit includes a resistor in series with a first capacitor operably connected between the passive transmitter's hot and neutral leads. The voltage-controlled switch is operably connected to the junction between the resistor and first capacitor of the RC circuit, such that the voltage-controlled switch is triggered into conductance at a predetermined phase of the alternating current (AC) waveform The SCR has a gate and two terminals: the first terminal is operably connected to the hot lead; second terminal is operably connected in series with the second capacitor; and the gate is operably connected to the second terminal of the voltage-controlled switch. As in known in the art, current flows through SCR upon application of appropriate biasing to SCR's gate. As a result, on every half cycle of the AC waveform flowing through the selected branch, the RC circuit biases the voltage-controlled switch into conductance which biases the gate of the SCR allowing current to flow through SCR and in turn to the second capacitor. Without any substantial resistance to limit current flow, the second capacitor charges instantaneously causing a large current flow from the circuit interrupter associated with the selected branch circuit. This current flows only during the period of time necessary to fully charge the second capacitor. Thus, this surge of current appears as a spike of very short duration on the particular branch circuit to which passive transmitter is connected. This chain of events occurs periodically at a frequency determined of the value of the RC circuit. In the one embodiment, the passive transmitter also has a "power-on" indicator that provides a visual cue that AC power is present when the passive transmitter is connected to a live branch circuit. In a second embodiment, the passive transmitter device comprises a variable resistor, a LED, an optocoupler, a thyristor, and a capacitor. The second terminal of the variable resistor is operably connected to the LED to adjust the intensity of the light emitted by the LED. In this embodiment, the optocoupler is operably located in proximity to the LED, such that the light emitted by the LED is converted to a corresponding voltage level on the output terminal of optocoupler. The gate of the thyristor is operably connected to the output terminal of the optocoupler. The thyristor's first terminal is operably connected to the hot lead wherein current flows between through the thyristor upon application of appropriate biasing to the gate of the thyristor. The second terminal of thyristor is operably connected in series with a capacitor. Operation of this embodiment is practically identical to that described with respect to the preferred embodiment.

In one potential embodiment, the receiver comprises a tank circuit, a detector amplifier circuit, and a power supply. The tank circuit is tuned to the predetermined frequency of the current spike signal. The detector amplifier circuit has an input terminal is operably connected to the tank circuit, and an output terminal is operably connected to the user-perceivable signaling device. The power supply is operably connected to detector amplifier circuit to provide a DC voltage source to its active internal components. With the power supply operably connected to the detector amplifier circuit, the detector amplifier circuit responds to the trigger voltage produced by tank circuit by producing an output signal that drives the user-perceivable signaling device .

In a preferred embodiment, the receiver includes a signal hold capacitor that is also operably connected to the output terminal of the detector amplifier circuit. The signal hold capacitor sufficiently prolongs the duration of the output signal produced by detector amplifier circuit to allow human perception of the user-perceivable signaling device.

In this preferred embodiment, user-perceivable signaling device includes audible and visual signaling devices. The audible and visual signaling devices form a first junction that is operably connected to the output terminal of the detector amplifier circuit. In this preferred embodiment, the signal hold capacitor includes an audible signal hold capacitor and a visual signal hold capacitor. The audible signal hold capacitor and the visual signal hold capacitor form a first junction that is also operably connected to the output terminal of the detector amplifier circuit. The values for the audible and visual signal hold capacitors are selected to prolong the output signal from the detector amplifier circuit that drives the audible and visual signaling devices, respectively, such that the output signal is in the frequency range that can be evaluated by human ears and eyes . In one embodiment of the present system, either the audible or visual signaling device is also configured to indicate availability of power for the detector amplifier circuit. In addition, the audible and visual signaling devices are operably connected to alternately produce an audible and a visual cues, respectively, in response to the output signal of amplifier detector circuit to ascertain if the present system is operational. In a preferred embodiment, the visual signaling device is a LED and the audible signaling device is a piezo electric buzzer. The present invention also includes a method for locating a circuit interrupter associated with a selected branch circuit from amongst a plurality of circuit interrupting devices, each circuit interrupter within said plurality of circuit interrupting devices being operably connected in series between a power line bus bar and a respective branch circuit, each branch circuit having a hot lead and a neutral lead, said system comprising: (a) operably connecting a passive transmitter to a selected branch circuit; (b) creating a current spike signal on the selected branch circuit at a predetermined frequency; (c) inducing only a substantially weak electromagnetic field about the selected branch circuit by limiting the current spike signal to a sufficiently short duration; (d) placing a receiver broadly tuned about the predetermined frequency of the current spike signal in physical proximity to each of the plurality of circuit interrupting devices individually; and (e) driving a user- perceivable signaling device when the receiver is coupled to the weak electromagnetic field generated at the predetermined frequency of the current spike signal . Brief Description of the Drawings

Fig. 1A of the drawings is a schematic diagram illustrating the various components in one potential embodiment of the passive transmitter of the present invention;

Fig. IB of the drawings is a schematic diagram illustrating the various components in a second potential embodiment of the passive transmitter of the present invention; Fig. 2 of the drawings is a schematic diagram illustrating the various components in a preferred embodiment of the receiver of the present invention; Fig. 3 of the drawings is an illustrative plot of a current spike signal produced by the passive transmitter of Fig. 1A; and

Fig. 4 of the drawings is a wiring diagram illustrating a potential AC power distribution panel providing power to a plurality of branch circuits through their respective circuit interrupting device.

Best Mode of Carrying Out the Present Invention While the present invention may be embodied in many different forms, there is shown in the drawings and discussed herein a few specific embodiments with the understanding that the present disclosure is to be considered only as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated.

The present system as disclosed herein locates the circuit interrupter associated with a particular branch circuit from amongst a plurality of circuit interrupting devices. Fig. 4 schematically depicts a potential AC power distribution panel 10 having three power line bus bars 60, 61 and 62 and a plurality of circuit interrupting devices (CB1, CB2 , CB3 , CB4 , CB5 and CB6) each connected in series between a respective bus bar and a respective branch circuit (40, 41, 42, 43, 44, and 45, respectively) . Although AC power distribution panel 10 uses circuit breakers, it would be understood by one of ordinary skill in the art that the present system would operate in the manner disclosed herein to locate any type of circuit interrupter device including, .but not limited to circuit breaker (s) and fuse(s) . As is known in the art, each circuit interrupter device provides overload protection to its associated branch circuit. While AC power distribution panel 10 reflects a balancing of power distribution loads (i.e. each power line bus bar distributes power to an equal number of branch circuits) , it should be understood that power does not have to be evenly distributed for the present system to operate in the manner disclosed herein.

Branch circuits 40, 41, 42, 43, 44, and 45 as shown in AC power distribution panel 10 are hot leads. Each branch circuit also includes a neutral lead (not shown in Fig. 4) that together with the branch circuit's hot lead supplies AC power to loads operably connected to the respective branch circuit .

The present system for locating a circuit interrupter associated with a particular branch circuit is comprised of two separate devices, a receiver and a passive transmitter. Figs. 1A and IB of the drawings depict two potential embodiments of the passive transmitter that can be used within the present system. Passive transmitters 100 and 200 have a hot lead (110 and 210) and a neutral lead (120 and 220) for operably connecting to a particular branch circuit. This connection may be accomplished by mating the transmitter to a selected branch via a standard power outlet (not shown) or by other standard means well known in the art. To illustrate operation of the present system, it is assumed that user has already connected one of passive transmitters 100 or 200 to branch circuit 40 in order to locate the circuit interrupter associated with that circuit.

Passive transmitter 100 preferably comprises a RC circuit 130, voltage-controlled switch 150, a Silicon Controlled Rectifier (SCR) 160, and a second capacitor 170. Upon connection of hot lead 110 and neutral lead 120 to the corresponding leads of a particular branch circuit, the aforementioned elements of passive transmitter 100 will cause a current spike signal to be drawn over branch circuit 40 from the associated power line bus bar 60. The transmitter is designed such that this current spike signal has a short pulse width and large amplitude so as to substantially minimize resulting sympathetic signals on adjacent branch circuits to, in turn, substantially eliminate false detection by a receiver.

Specifically, RC circuit 130 includes resistor 131 which is operably connected in series with a first capacitor 132 to form a phase shifting network. RC circuit 130 is operably connected between hot lead 110 and neutral lead 120. Circuit 190 is an optional "power-on" indicator that shows whether the circuit is "live."

Voltage-controlled switch 150, which is shown in Fig. 1A as a diac, has a first terminal 151 and a second terminal 152. The first terminal 151 of voltage-controlled switch 150 is operably connected to the junction between resistor 131 and first capacitor 132 of RC circuit 130. RC circuit 130 is constructed to trigger voltage-controlled switch 150 into conductance at a predetermined phase of each half cycle of the alternating current (AC) waveform.

SCR 160 has a gate 161, a first terminal 162 and a second terminal 163 wherein current flows between the first and second terminals (and thus through SCR 160) upon application of appropriate biasing to gate 161. The first terminal of SCR 160 is operably connected to hot lead 110 and the second terminal of SCR 160 is operably connected in series with second capacitor 170. The gate of SCR 160 is operably connected to second terminal 152 of voltage-controlled switch 150. Thus, on every half cycle of the AC wave, RC circuit 130 biases voltage-controlled switch 150 into conductance which then biases gate 161 of SCR 160, allowing current to flow through SCR 160 and in turn through second capacitor 170. Without any substantial resistance to limit current flow, second capacitor 170 charges instantaneously causing a large current flow through circuit breaker 20 and branch circuit 40 to passive transmitter 100. This current flows only during the period of time necessary to fully charge second capacitor 170. Thus, this current surge appears as a spike of very short duration on particular branch circuit to which the passive transmitter is connected. When the polarity of the AC waveform on associated power line bus bar 60 changes, the forward charging of second capacitor 170 ceases. Furthermore, voltage-controlled switch 150 reverts from a conductive to a blocking state once the voltage across it reaches its minimum level, removing the bias to the gate of SCR 160. Yet, the second capacitor discharges through the SCR before it returns to its blocking state. Because the biasing of voltage- controlled switch 150 and SCR 160 are not effected by voltage polarity, the second capacitor 170 will again be charged instantaneously, as described above. As long as AC power is present on particular branch circuit 40 to which passive transmitter is connected, this current spike will be periodically produced as described above.

This current spike signal in branch circuit 40 increases the electromagnetic field to surround branch circuit 40. Unavoidably a current spike will be generated on any branch circuits adjacent to the particularly selected branch circuit (i.e., branch circuit 40). However, because the current spike signal produced by passive transmitter 100 is of significantly short duration and large amplitude, there is insufficient time for a full strength sympathetic signal to develop in the other, unselected branch circuits. Consequently, the difference in signal strength between the current spike signal produced by passive transmitter 100 on the particularly selected branch circuit and any sympathetic signals developed on any adjacent branch circuits is of such a range that they can easily be distinguished from one another.

Fig. 3 of the drawings shows the current spike signal developed as described above for passive transmitter 100 with resistor 131 having a value of 470 kilo-ohms, first capacitor 132 having a value of 0.1 microfarads, and second capacitor 170 having a value of 0.68 microfarads. As shown, the resulting current spike signal has a magnitude on the order of 30 amps and a pulse width duration on the order of 500 nanoseconds. As would be known to one of ordinary skill in the art, additional loads and associated impedances on a particular branch circuit will likely change the resulting amplitude and duration of the current spike signal.

It would also be known to one of ordinary skill in art that the present system as disclosed herein would operate in the same manner with 60 Hz AC power as is common in the United States and with 50 Hz AC power line as is commonly found in countries foreign to the United States.

In a preferred embodiment of passive transmitter 100, voltage-controlled switch 150 is a DIAC and SCR 160 is a

TRIAC. In one embodiment, the DIAC and SCR functionality can be combined in one discrete unit, such as Q2004 manufactured by Teccor Electronics, Inc. of Irving, Texas, thus lowering component count and overall cost. As previously mentioned, Fig. IB of the drawings shows another potential embodiment of the passive transmitter component of the present system. Again, while the present system can mate to any outlet or the like of any branch circuit such as shown in AC power distribution panel 10 of Fig. 4, for the purpose of illustrating the manner of operation of the present system, passive transmitter 200 is assumed to be operably connected to particular branch circuit 40. Passive transmitter 200 comprises variable resistor 230, LED 240, optocoupler (part of 250 as shown in Fig. IB and noted hereafter as 251) , thyristor (also part of 250 as shown in Fig. IB and noted hereafter as 252), and capacitor 260. Variable resistor 230 has a first terminal 231, a second terminal 232, and an adjustment control terminal 233. The first terminal 231 and the adjustment control terminal 233 are operably connected to hot lead 210. The second terminal 232 of variable resistor 230 is operably connected to LED 240. The variable resistor 230 is set via adjustment control terminal 233 to limit current flow through LED 240 at a predetermined voltage level of the AC flowing through the hot lead 210. Thus, the intensity of light emitted by LED 240 is adjusted accordingly. Optocoupler 251 includes a photodiode (not shown in Fig. IB) and an output terminal (not shown in Fig. IB) . In the preferred embodiment of the present system, optocoupler 251 is operably located in physical proximity to LED 240, wherein the light emitted by LED 240 is converted to a corresponding voltage level on the output terminal of optocoupler 251.

Thyristor 252 has a gate (not shown in Fig. IB) , a first terminal and a second terminal . The gate of the thyristor is operably connected to the output terminal of the optocoupler 251, wherein current flows between the first and second terminals and through said thyristor 252 upon application of appropriate biasing of the gate of the thyristor. The first terminal of thyristor 252 is operably connected to hot lead 210. The second terminal of thyristor 252 is operably connected' in series with a capacitor 260. Thus, on every positive half cycle of AC flowing through branch circuit 40, LED 240 is illuminated resulting in optocoupler 251 biasing the gate of the thyristor, allowing current to flow through the terminals of thyristor and, in turn, through capacitor 260. Capacitor 260 charges instantaneously developing a current spike signal on branch circuit 40. The current spike signal duration and amplitude generated by passive transmitter 200 is similar to that produced by passive transmitter 100 and shown in Fig. 3.

Consequently, the current spike signal generated by passive transmitter 200 upon establishment of connection to particular branch circuit 40 is also easily detectable because development of sympathetic signals on other adjacent branch circuits is substantially inhibited.

In the preferred embodiment of passive transmitter 200, LED 240, optocoupler 251, and thyristor 252 are enclosed within a single package.

As shown in Fig. IB, passive transmitter 200 includes an optional power-on indicator lamp 290 adapted to be operably connected to variable resistor 230. Power-on indicator lamp 290 provides a visual indication that AC power is present on hot lead 210 when passive transmitter 200 is connected to particular branch circuit 40. Fig. 2 of the drawings depicts a potential embodiment of the present system's receiver unit. Receiver 300 is broadly tuned about a predetermined frequency of the current spike signal created on particular branch circuit 40 by the passive transmitter of the present system. Receiver 300 drives a user-perceivable signaling device 350 that is activated when receiver 300 senses a signal with the predeterminated frequency.

As shown in Fig. 2, a potential embodiment of receiver 300 comprises a tank circuit 310, a detector amplifier circuit 330, and a power supply 360. Tank circuit 310 has an inductor 311 operably connected in parallel to capacitor 312. The coil of inductor 311 senses the electromagnetic field produced by the current spike signal on the particularly selected branch circuit to which a passive transmitter of the present system is connected. Tank circuit 310 is constructed to resonate upon receipt of the predetermined frequency of the passive transmitter thereby smoothing out the sensed current spike signal and producing a trigger voltage of short duration.

In a preferred embodiment, detector amplifier circuit 330 is a LM3909 LED Flasher/Oscillator manufactured by National Semiconductor Corporation of Arlington, Texas and configured as for an AM radio receiver. As shown in Fig. 2 for the preferred embodiment of detector amplifier circuit 330, only pins 2, 4, 5, and 8 of a LM3909 are operably connected within receiver 300. Detector amplifier circuit 330 has an input terminal 331 corresponding to pin 8 of a LM3909 that is operably connected to tank circuit 310. Detector amplifier circuit 330 also has an output terminal 332 corresponding to pin 2 of a LM3909 that is operably connected to user- perceivable signaling device 350.

In addition, power supply 360 is operably connected to detector amplifier circuit 330 to provide a voltage source to its active internal components. Because a LM3909 which has a low current drain is used for detector-amplifier circuit 330 in a preferred embodiment, power supply 360 is preferably a low voltage battery. However, as would be known to one of ordinary skills in the art, power supply 360 can be comprised of various components that combine to form a low voltage DC power source. For instance, in another potential embodiment (not shown) power supply 360 may include a step-down transformer connected to an AC source coupled to a filtered recti ier. While switch 370 is closed power is operably connected to detector amplifier circuit 330, as a result the detector amplifier circuit 330 responds to any trigger voltage produced by tank circuit 310 by producing an output signal that drives user-perceivable signaling device 350.

In the preferred embodiment of receiver 300 a signal hold capacitor 340 is operably connected to output terminal 332 of detector amplifier circuit 330 to prolong the duration of the output signal produced by detector amplifier circuit 330 to allow human perception of the signal generated by user- perceivable signaling device 350.

In a preferred embodiment of the present system, user- perceivable signaling device includes an audible signaling device 351 and a visual signaling device 352. The audible signaling device 351 and the visual signaling device 352 form a first junction 353 that is operably connected to output terminal 332 of the detector amplifier circuit. Also in a preferred embodiment of the present system, signal hold capacitor 340 includes separate audible and visual signal hold capacitor 341 and 342. Audible signal hold capacitor 341 and visual signal hold capacitor 342 form a first junction that is operably connected to output terminal 332 of the detector amplifier circuit. The value of the audible signal hold capacitor is selected to prolong the detector amplifier output signal such that the output signal is in the frequency range that can be evaluated by human ears. Similarly, the value of the visual signal hold capacitor is selected to prolong the detector output signal such that the output signal is in the frequency range that can be evaluated by human eyes .

In addition, in this potential embodiment of the present system, either audible signaling device 351 or visual signaling device 352 is also configured to indicate availability of power for detector amplifier circuit 330 regardless of whether a current spike signal has been sensed by tank circuit 310. Hence, in the embodiment of receiver 300 shown in Fig. 2, when switch 370 is open both audible signaling device 351 and visual signaling device 353 are not activated. When switch 370 is closed, power is supplied to amplifier detector circuit 330 which maintains a positive voltage on output terminal 332 when no trigger voltage is present on its input terminal 331, hence activating the visual signaling device to provide a "power-on" indication while the audible signaling device 351 remains off.

Furthermore, in the preferred embodiment of the present system, the audible and visual signaling devices are operably connected to alternately produce audible and visual cues.

Thus, in the embodiment of receiver 300 shown in Fig. 2, when the amplifier detector produces an output signal in response to a trigger voltage input as disclosed above, the audible signaling device 351 is activated and visual signaling device 352 is deactivated. Hence, without adding complex circuitry to the present system, the operator can distinguish if the detector-amplifier circuit 330 is receiving power (i.e. when visual signaling device 352 is activated) and if the receiver 300 is operational (i.e. when visual signaling device 352 or audible signaling device 351 are periodically activated) . In one potential embodiment of receiver 300 shown in Fig. 2, visual signaling device 351 is a LED and audible signaling device 352 is a piezo electric buzzer.

Although passive transmitter of the present system as disclosed does not modulate the current spike signal it produces, receiver 300 would still function in the manner disclosed if the current spike signal were modulated by a AM program signal. Receiver 300 would separate the AM program signal from the current spike signal carrier, then amplify the AM signal before passing it on to the user-perceivable signaling device 350. Even though the contemplated AM program signal may cause user-perceivable signaling device 350 to be activated erratically, it still provides an indication that the current spike signal has been sensed by receiver 300 of the present system.

It should be noted that any receiver capable of picking up a predetermined signal can be used in association with the passive transmitters disclosed herein.

The preferred embodiment of receiver 300 is intended to be packaged as a hand held device. This allows an operator, who is attempting to locate the circuit breaker associated with the particularly selected branch circuit (to which passive transmitter 100 or 200 is connected) to move and orient receiver 300 such that tank circuit 310 can be positioned in close proximity to each circuit interrupter in AC Distribution Panel 10. When a potential embodiment of the present system is operated as disclosed herein with passive transmitter 100 or 200 operably connected to particular branch circuit 40, the user-perceivable signaling device 350 will provide the user with a audible and visual cue when receiver 300 is in close proximity to circuit breaker 20 through which the current spike signal is flowing. Again, due to the short duration and maximal amplitude of the current spike signal generated on the particular branch circuit 40 by passive transmitter 100 or 200, the user can correctly locate circuit breaker 20 to the exclusion of other adjacent circuit breakers (i.e. 21, 22, 23, 24, and 25) because the present system effectively precludes the development of a significant, sympathetic current spike signal. This allows the user to confidently locate a desired circuit interrupter and remove power to the associated branch circuit on which work is to be performed. Because the aforementioned embodiments of the passive transmitter and receiver of the present system are comprised of commercial-off-the-shelf components and are not complex circuits to implement, the present system is of low cost to produce .

Claims

WHAT IS CLAIMED IS:

1. A system for locating a circuit interrupter associated with a selected branch circuit from amongst a plurality of circuit interrupting devices, each circuit interrupter within said plurality of circuit interrupting devices being operably connected in series between a power line bus bar and a respective branch circuit, each branch circuit having a hot lead and a neutral lead, said system comprising: a receiver broadly tuned about a predetermined frequency of a current spike signal created on said selected branch circuit by a passive transmitter, said receiver driving a user-perceivable signaling device upon sensing said current spike signal; and said passive transmitter creating said current spike signal on said selected branch circuit at said predetermined frequency upon operable connection to said selected branch circuit, said current spike signal having a sufficiently short spike duration so as to substantially minimize development of a sympathetic signal on other branch circuits adjacent to said selected branch circuit; whereby said receiver detects said current spike signal solely when in proximity to said circuit interrupter associated with said selected branch circuit as said current spike signal on said selected branch circuit is easily distinguished from said sympathetic signal developed on any of said other branch circuits.

2. The system according to Claim 1 wherein said receiver includes :

- a tank circuit tuned to said predetermined frequency of said current spike signal generated by said passive transmitter on said selected branch circuit; - a detector amplifier circuit, having an input terminal and an output terminal, said tank circuit operably connected to said detector amplifier circuit input terminal;

- said detector amplifier circuit output terminal operably connected to said user-perceivable signaling device, wherein upon sensing said current spike signal said tank circuit produces a trigger voltage causing said detector amplifier to produce an output signal that drives said user- perceivable signaling device; and - a power supply operably connected to said detector amplifier.

3. The system according to Claim 2 further comprising a signal hold capacitor operably connected to said detector amplifier output terminal.

4. The system according to Claim 3 wherein said user- perceivable signaling device includes an audible signaling device and a visual signaling device, each of said audible signaling device and said visual signaling device having a first junction that is operably connected to said detector amplifier output terminal.

5. The system according to Claim 4 wherein said signal hold capacitor includes an audible signal hold capacitor and a visual signal hold capacitor, each of said audible and visual signal hold capacitors having a first junction that is operably connected to said detector amplifier output terminal.

6. The system according to Claim 4 wherein said audible and visual signaling devices are operably connected to alternately produce respective cues in response to said amplifier detector output signal.

7. The system according to Claim 6 wherein one of said audible and visual signaling devices is also configured to indicate availability of power for said receiver.

8. The system according to Claim 1 wherein said current spike signal has a spike duration no longer than about 500 nanoseconds .

9. The system according to Claim 1 wherein said passive transmitter includes: a RC circuit including . a resistor and a first capacitor, said RC circuit being operably connected between said hot lead and said neutral leads of said selected branch circuit ; - a voltage-controlled switch having a first terminal and a second terminal, said first terminal of said voltage-controlled switch is operably connected to the junction between said resistor and said first capacitor of said RC circuit; said RC circuit constructed to trigger said voltage-controlled switch into conductance at a predetermined phase of an alternating current (AC) flowing through said hot lead of said selected branch circuit; a Silicon Controlled Rectifier (SCR) having a gate, a first terminal and a second terminal wherein current flows between said first and second terminals and through said SCR upon application of appropriate biasing to said gate, said SCR being operably connected in series with a second capacitor between said hot and neutral leads of said selected branch circuit, said gate of said SCR being operably connected to said second terminal of said voltage-controlled switch, whereby on every half cycle of said AC flowing through said selected branch circuit, said RC circuit biases said voltage-controlled switch to conduct, causing the gate of said SCR to be biased, in turn, allowing current to flow through said SCR and to the second capacitor, said second capacitor charges instantaneously developing current spike signal on said selected branch circuit .

10. The system according to Claim 9 wherein said voltage-controlled switch is a DIAC.

11. The system according to Claim 9 wherein said SCR is a TRIAC.

12. The system according to Claim 9 further comprising a power-on indicator circuit adapted to be operably connected to said hot lead of said desired branch circuit.

13. The system according to Claim 1 wherein said passive transmitter includes: - a variable resistor operably connected to said hot lead of said selected branch circuit; a LED having its anode operably connected to said variable resistor, wherein said variable resistor is set to limit current flow through said LED at a predetermined voltage level of said AC flowing through said selected branch circuit and thereby limit light intensity emitted by said LED;

an optocoupler operably located in proximity to said LED, said optocoupler having an output terminal; and - a thyristor, having a gate, a first terminal and a second terminal wherein current flows between said first and second terminals and through said thyristor upon application of appropriate biasing to said gate, said thyristor being operably connected in series with a capacitor between said hot and neutral leads of said selected branch circuit; whereby on every positive half cycle of said AC flowing through said particular branch circuit, said optocoupler biases said gate of said thyristor, allowing current to flow through said terminals of thyristor and in turn to the capacitor, said capacitor charges instantaneously developing said current spike signal on said selected branch circuit .

14. The system according to Claim 13, wherein the LED, optocoupler, and thyristor are enclosed within a single package

15. The system according to Claim 14 further comprising a power-on indicator lamp adapted to be operably connected to said variable resistor.

16. A passive transmitter for use in a system for locating a circuit interrupter associated with a selected branch circuit from amongst a plurality of circuit interrupting devices, each circuit interrupter within said plurality of circuit interrupting devices being operably connected in series between a power line bus bar and a respective branch circuit, each branch circuit having a hot lead and a neutral lead, said passive transmitter comprising: - a RC circuit including a resistor and a first capacitor, said RC circuit being operably connected between said hot lead and said neutral leads of said selected branch circuit ; a voltage-controlled switch having a first terminal and a second terminal, said first terminal of said voltage- controlled switch is operably connected to the junction between said resistor and said first capacitor of said RC circuit; said RC circuit constructed to trigger said voltage- controlled switch into conductance at a predetermined phase of an alternating current (AC) flowing through said hot lead of said selected branch circuit;

- a Silicon Controlled Rectifier (SCR) having a gate, a first terminal and a second terminal wherein current flows between said first and second terminals and through said SCR upon application of appropriate biasing to said gate, said SCR being operably connected in series with a second capacitor between said hot and neutral leads of said selected branch circuit, said gate of said SCR being operably connected to said second terminal of said voltage-controlled switch,

- whereby on every half cycle of said AC flowing through said selected branch circuit, said RC circuit biases said voltage-controlled switch to conduct, causing the gate of said SCR to be biased, in turn, allowing current to flow through said SCR and to the second capacitor, said second capacitor charges instantaneously developing a current spike signal on said selected branch circuit, said current spike signal having a predetermined frequency and a sufficiently short spike duration so as to substantially minimize development of a sympathetic signal on other branch circuits adjacent to said selected branch circuit.

17. A method for locating a circuit interrupter associated with a selected branch circuit from amongst a plurality of circuit interrupting devices, each circuit interrupter within said plurality of circuit interrupting devices being operably connected in series between a power line bus bar and a respective branch circuit, each branch circuit having a hot lead and a neutral lead, said system comprising:

(a) operably connecting a passive transmitter to a selected branch circuit;

(b) creating a current spike signal on the selected branch circuit at a predetermined frequency;

(c) inducing only a substantially weak electromagnetic field about the selected branch circuit by limiting the current spike signal to a sufficiently short duration;

(d) placing a receiver broadly tuned about the predetermined frequency of the current spike signal in physical proximity to each of the plurality of circuit interrupting devices individually; and (e) driving a user-perceivable signaling device when the receiver is coupled to the weak electromagnetic field generated at the predetermined frequency of the current spike signal .