US2774960A - Current failure indicator - Google Patents

Description

United States Patent O CURRENT FAILURE INDICATOR Howard I. Podell, Mamaroneck, N. Y.

Application January 6, 1954, Serial No. 402,425 Claims. (Cl. 340-250) This invention relates to automatic indicating systems for electrical networks and more specifically to a new and improved circuit and arrangement of components for providing a visual indication upon the interruption of current through one or more load circuitspowered by a low voltage supply.

Many systems have been developed for use in connection with power supply and distribution systems to indicate interruption of power in a particular part thereof through overloading the circuits and causing the protecting devices such as circuit breakers or fuses to break the circuit. In conventional 110 volt systems where voltage limitations do not present a problem, conventional lamps or other indicators may be used. Gas filled lamps such as neon tubes and the like can be employed on such power systems wherein the nominal voltage is above the starting voltage for the gas tube by directly connecting them across the circuit breaking means. In low voltage circuits, however, and particularly in portable low voltage systems wherein efliciency in the utilization of power is of prime importance, prior alarm and indicating systems known-to me are not directly applicable and complicated and expensive mechanical systems have therefore been used. Accordingly, this invention has as one of its objects a new and improved alarm system for low voltage circuits characterized by its simplicity, low cost, instantaneous action and dependability. These ends are accomplished through the provision of a circuit including cold cathode gas filled indicating lamps wherein a lamp immediately responds to the interruption of current through one or more loads and thus imparts to the operator information concerning the condition of the circuits at all times. 2

Another object of the invention is a new and improved alarm system for low voltage electric distribution' systems that will draw negligible current and at the same time not only detect failure of current through a load circuit by reason of the opening of a fuse, switch, or circuit breaker but also provide an alarm upon the failure of current in a load circuit produced by failure of a load to draw current by reason of an open switch or fuse in the load itself.

' Still another object of the invention is an improved electrical network alarm and indicating system that not only provides an indication of the condition of the network at all times but also provides means for periodically testing the alarm system to ascertain its operativeness and determine whether or not the alarm system or part thereof has failed.

Theabove and other objects and advantages of the invention will become more apparent from the following description and accompanying drawings forming part of this application.

In the drawings:

Fig. 1 is a circuit diagram illustrating one embodiment of-the invention; I

"ice

Fig. 2 is a circuit diagram showing another embodiment of the invention; and

Fig. 3 is still another modification of the invention.

Briefly the invention provides an improved alarm or indicating circuit embodying one or more gas filled lamps, such as neon lamps or the like coupled with an electrical distribution network and a supplemental source of power so that failure of current in a given section of the network will produce a voltage in series with an associated lamp and the supplemental source so that the total voltage impressed upon the lamp will be sufficient to cause it to ionize and glow. With this circuit each indicating lamp may be located adjacent the load or fuse or it may be at a remote location depending upon the requirements of the specific application. More specifically and with reference to Fig. l which illustrates an electrical power distribution system and an alarmv in accordance with the invention, the primary source of power is indicated by a battery 10 connected between two energy distributing conductors 11 and 12. A series of. loads such as motors, heaters, or other radio or electrical equipments are denoted by the numerals 13 to 16 inclusive. The terminals 13 to 16 of each load are connected directly to the conductor 12 while the other terminals13 to 16" are connected through current interrupting means 17 to 20 inclusive to the other conductor 11. The current interrupting means 17 to 19 are illustrated as fuses which function to open the circuit to the load in the event excess current is drawn. It is evident that circuit breakers or switches may be used in place of the fuses without modifying or otherwise altering the alarm circuit. This is illustrated in connection with load 16 wherein switch 20 is in series therewith.

The alarm system includes a separate source of power represented by. the battery 21 connected between conductor 11 and an alarm conductor 22. The battery 21 is phased with the battery 10 so that their voltages will add and the total voltage will be measurable between conductors 12 and 22. A bank of neon lamps or other equivalent low current indicators 23 are connected to the conductor 22 and through associated resistors 27 to 30 to the terminals 13" to 16" of the respective loads. With this arrangement should the fuses 17 to 19 or switch 20 be open, the associated neon light 23 to 26 will then receive the sum of the voltages of sources 21 and 10. In the case of the load 13, should fuse 17 open, the total voltage of the system would be applied to the neon tube 23 through the series circuit including resistor 27 and load 13 with the resistor 27 functioning as a current limiting device so that the drain of the tube will be maintained at a negligible value.

In order to test the system to determine whether or not the auxiliary battery 21 or other power source has sufficient voltage so that the sum of it and the primary source is suflicient to ionize and illuminate the neon lamps 23 to 26, a test circuit is provided. This circuit includes two series connected resistors 31 and 32 and a series switch 33 connected between the conductors 12 and 22. A neon test'lamp 34 is connected in parallel with the resistor 31. The resistors 31 and 32 are proportioned one relative to the other so that the ionizing voltage applied to lamp 34, when switch 33 is closed, is only slightly above that required by the lamp 34 with both the power sources 21 and 10 at normal voltage. In this way lighting of lamp 34 in the test circuit will indicate that battery 21 not only has sufficient voltage to illuminate lamps 23 to 26 as described but is well beyond the critical value.

The foregoing embodiment of the invention illustrates the advantages of this improved alarm system in power networks where the nominal supply voltage is below that required to ionize a neon lamp. Moreover the neon lamps draw only negligible current so that the auxiliary supply need only be a miniature battery of the desired potential. In the case of A. C. systems, the auxiliary supply 21 must of course be phased with :the basic supply 1% in order to get the effect. If desired the auxiliary supply 21 in an A. C. system may comprise a D. C. source in which case phasing is unnecessary.

Fig. 2 is another embodiment of the invention wherein a single lamp is used to indicate failure of current through one or more loads. As in the case of Fig. 1 the loads 35, 36, and 27 in series with their associated fuses 39 to 46 are connected between supply conductors 11 and 12 which in turn connect with the primary source 10. The signalling or alarm system includes a single neon tube indicator 41 having one side connected through separate resistors 42, 43, and 44 to the fuse side of the loads 35 to 37, respectively. The other side of the lamp 41 is connected through resistor 45 to one terminal of the auxiliary source 21 and which has its other terminal connected to conductor 11. With the circuit thus far should one of the fuses, as for instance fuse 3.8, open, the sum of voltages 21 and will be applied to the neon lamp 41 through load and resistors 42 and 45. The shortcircuiting efiect of resistors 43 and 44 will be negligible since their values usually exceed 100,000 ohms. The resistor 45 is optional and would only be used in instances wherein the sum of the voltages sources 21 and Ill is relatively high and added current limiting, over and above that provided by resistors 42 to 44, is needed.

The test circuit includes a series connected switch 46 and resistor 47 coupled between the conductor 12 and the junction of lamp 41 with resistors 42 to 44. When switch 46 is closed the total voltage is applied to lamp 41 through resistors 47 and 45 in order to illuminate it and check its operation. The resistor 47 is of course proportioned relative to the other resistors so that an ionizing volta e only slightly in excess of that required is applied to the lamp. In this way the increased voltage on the lamp 41 when current through one of the loads is interrupted will be considerably above the critical ionizing voltage.

In certain instances, it may be desirable to indicate not only the opening of a fuse in series with a load but also opening of the load itself through a failure which not only blows the fuse but also causes the load itself to open. This end may be accomplished with a circuit configuration as shown in Fig. 3. While only a single load is illustrated it will become apparent that the system may be used with any number of loads. figure the load 43 with a series connected fuse 49 is connected across the primary source of power 10. The indicator lamp 549 has one side connected to the auxiliary source 21 which in turn is connected with the primary source 10. The other side of lamp 50 is connected through series resistors 51 and 52 to one side of load 48 while the juncture of resistors 51 and 52 is connected to the juncture of fuse 49 and load 48. Now in the event the fuse 49 opens, the indicator 50 will be illuminated by the total voltage of sources through the circuit including load 48 and resistor 51. Should the 102141 48 be opened in addition to blowing of the fuse 49 the indicator 55 will still be illuminated by reason of the interconnection of the resistor 52 with resistor 51 and load 48.

The embodiment of the invention of Fig. 3 may of course be used in connection with the embodiments of Figs. 1. and 2 and similar test circuits may be employed.

While only certain embodiments of the invention have been shown and described it is apparent that other modiiications, changes and alterations may be made without departing from the true scope and spirit thereof.

Having thus described my invention, .1 claim:

In an electrical power distribution system having a primary source of power, means for connecting at In this I least one load therewith and current interrupting means in series with said load, an alarm for indicating failure of current in said load comprising an auxiliary power source having one terminal connected to one side of said primary power source, a cold cathode indicator lamp having an ionizing voltage greater than the voltage of said primary power source and greater than the voltage of said auxiliary power source and less than the combined voltage of the auxiliary power source and the primary voltage source, a connection between one terminal of said lamp and the other terminal of said auxiliary source and a connection between the other terminal of said lamp and the junction of said interrupting means and said load whereby opening of said interrupting means will apply a voltage to said lamp approximately equal to the sum of said power sources.

2. In an electrical power distribution system according to claim 1 wherein said alarm system includes a current limiting resistor in series with said indicator lamp.

3. In an electrical power distribution system according to claim 1 wherein said alarm system includes a current limiting resistor in series with said indicator lamp and a second resistor in parallel with said load.

4. In a power distribution system having a primary source of power, means for connecting at least one load therewith and current interrupting means in series with said load, an auxiliary power supply, a cold cathode indicator lamp having an ionizing voltage greater than the voltage of either the primary source of power and the auxiliary power supply separately and less than their combined voltages, a connection between one terminal of said auxiliary source and said primary power source to place both of said sources in series one with the other, a connection between one terminal of said indicator lamp and the other terminal of said auxiliary power source, and connections between the other terminal of said lamp and the junction of each of said loads with its associated current interrupting means, whereby interruption of current through one or more loads will apply an increased voltage to said indicator lamp to illuminate it.

5. In a power distribution system according to claim 4 wherein each connection between said lamp and each of said loads includes a current limiting resistor.

6. In a power distribution system according to claim 4 wherein each connection between said lamp and said loads includes a current limiting resistor and wherein means including a switch and a current limiting resistor is connected between said other terminal of said lamp and the primary power source whereby closing of said switch will apply the voltage of both of said sources to said lamp to test the operation thereof.

7. In a power distribution system according to claim 4 wherein each connection between said lamps and each of said loads includes a current limiting resistor and each of said loads is provided with a resistor connected in parallel therewith.

8. A power distribution and current vfailure alarm system comprising a primary power source and an auxiliary power source connected in series one with the other to provide a voltage equal to their sum across the outer terminals of said sources, means for connecting at least one load across said primary source with current interrupting means in the connection between said load and the junction of said power sources, a cold cathode indicating lamp having one terminal connected to the outer terminal of said auxiliary source and the other terminal to the juncture of said load and current interrupting means, said cold cathode indicating lamp having an ionizing voltage greater than the voltage of either said primary source and said auxiliary power source separately but less than their combined voltages.

9. A power distribution and alarm system according to claim 8 wherein said cold cathode indicator lamp includes a current limiting resistor in series therewith.

10. In an electrical power distribution system having a primary source of power, means for connecting a plurality of loads therewith and a current interrupting means in series with each of said loads, an alarm for indicating failure of current in each of said loads comprising an auxiliary power source having one terminal connected to one side of said primary power source, a plurality of cold cathode indicator lamps each having an ionizing voltage greater than either the voltage of said primary power source and said auxiliary power source separately and less than the combined voltages of the primary source of power and the auxiliary power source, a connection between one terminal of each of said lamps and the other terminal of said auxiliary source and a connection between the other terminal of each of said lamps and the junction of one of said interrupting means and its connected load whereby opening of each of said interrupting means will apply a voltage to its connected lamp approximately equal to the sum of said power sources.

References Cited in the file of this patent UNITED STATES PATENTS 2,036,223 Lapple Apr. 6, 1936 2,317,030 Colvin Apr. 20, 1943 2,464,848 Collins Mar. 22, 1949

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