US832577A - Time-limit circuit-breaker. - Google Patents

Description

INo. 832,577, PATENTED OCT. 2, 1906.

E. M. HEWLETT.

TIME LIMIT CIRCUIT BREAKER.

APPLICATION runnrnxn, 1899. RENEWED OOT.18, 1901.

2 SHE-ETSSHEET 1.

WI TNEESES. Q 7 I lNvENT lR- I 62 IE? v3-9. I): Edww M.][ewlett.

'IATENTED OCT. 2, 1906.

E. M. HEWLETT. TIME LIMIT CIRCUIT BREAKER.

APPLICATION FILED PERU, 1899. RENEWED 00118, 1901.

2 SHEETSSH1:ET 2.

' INVEN UF Edward M..]'[ewlefi- WITNESSES.

UNITED STATES PATENT OFFICE.

EDWARD M HEWLETT, OF SCHENEOTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

TIME-LIMIT QlRCUlTrBREAKER.

Specification of Letters Patent.

Patented Oct. 2, 1906.

Applioatibn filed February 11, 1899. Renewed October 18. 1901. Serial No. 79,149.

Schenectady, in the county of Schenectady and State of New York, have invented cer- "tain new and useful Improvements in Time- Limit CircuitBreakers, of which the following is a s ecification. a

t has itherto been customary to provide electric circuits with safety devices consisting of switches arranged to 0 n automatically when the current reache a predetermined value. Such devices have in practice proved insufficient and objectionable, since they have opened upon merely momentary over loads and have responded merely to current strength independent. of the time during which the current might be maintained. An ordinary electric circuit or translating device can endure for brief periods overloads which would be destructive if carried for long times, and it is highly inconvenient to have the apparatus rendered useless on i every merely momentary rise of current beyond the limit which the circuit is designed to endure continuously. As an example of the utility of the combination here pointed out I may instance a large electric railway system on which a number of cars are running. It may well happen that a large number of cars upon the same section or upon a part of the road fed by the same .feeder and supplied through a single circuit-breaker may start at one time, and the current requirements will be so great that under ordinary conditions the circuit-breaker would operate,yet the generator or station might well be able to carry the overload for some little time with out injury, and it would cause great moon-- venience to have the feeder opened. As the cars acquire speed the current requirements are cut down in the usual way, and such an overload might not persist for any considerable length of time, and therefore the operation of the circuit-breaker would be only a source of annoyance; but if the same current were taken by a ground or in any other way taken continuously it would be desirable to open the feeder.

A further utility of the invention will be found in the case of alternating-current lines. stance, there sometimes occurs what is known as surging, in which action the curand the circuit-breaker opened.

be described.

In lines of high potential, forin.

rent and potential are subject to violent fluctuations or to a sort of harmonic rise and fall, burning off wire, kite-wires, &c. These phenomena are often, (and, in fact, enerally) of such brief duration that it is hi y undesirable to open the circuit when th y occur. In such cases my invention would come into play.

vention I have shown it as it has been apphed to three-phase lines carrying alternatcurrents; but this is only a type of any in other system in which it may be usefully applied,and the particular application herein set forth is to be taken astypical of any other embodiment embracing its principles.

Automatic circuit-breakers of ordinary c0nstructionsuch,.for instance, as those described in the patent to W. B. Potter, No. 533,083, in which a spring-operated contact of switching device is released by an overload-coil-are inserted in the various lines.

As a convenient exemplification of the in- A clockwork mechanism capable of tripping the circuit-breaker'is held from rotation by a. I

suitable detent actuated by the armature of the series coil. On account of the difficulty in actuating the trip ositively by ordinary clockwork devices I ave preferred to relay it, as it is calledthat is, to make the clock close the circuitand thus actuate a coil which .will trip the circuit-breaker positively. Obviously other arrangements might be used. The detent is so arranged in cooperation with a suitable lug on one of the wheels of the clock that only after the lug has made a practically complete revolution will the circuit of the relay-coil be completed If during the time of this revolution the overload or short-circuit be removed, the lug will be stopped, so that the circuit of the relay device will not be completed.

The arrangement of the invention just outlined is of great importance and utility. It has, however, limitations which I aim to avoid in a second form of apparatus now to It may be that an ordinary overload for which the machinery is proportioned and which it is intended to stand for a reasonable time would do no damage within the time limit; but it may also wellhappen that a short-circuit or dangerous overload may occur during thistime, and it would be disastrous to permit th' is large current to flow .even

i for the time limit, however short that might I therefore by the second form of apparat-us now to be described so arrange the device that although the time feature is still in play for all ordinary overloads up to the resented I provide for this condition by ineluding in multiple with the trippingecoil of the circuit-breaker a resistance so proportioned that the drop across its terminals at the determined second overload is sufficient to cause current enough to pass through the tripping-coil to operate the circuit-breaker. Thus, for example, in a circuit-breaker set toopen on an overload of fifty per cent, which is a common practice in the art, the time-limit feature will be called into play as soon as the current reaches this amount. Should, however, a real short-circuit occur. or an overload of a hundred per cent., which would be dangerous, then the drop across the resistanceterminals will drive enough current through the tripping-coil to open the circuit-breaker at once.

One feature of my invention therefore jembodies a circuit breaking 01' switching apparatus having two operating conditions, both in play at the same time-that is to say, a circuit-breaker which will open at a predetermined overload existing for a. definite length of time and will also open instantaneously when the overload reaches a certain other predetermined and higher limit, and the claims which I shall make to this feature are to be regarded as generic.

As an additional and auxiliary feature of invention I have shown in this case a number of independent switches, each of which is capable of independent actuation to open or close its circuit and all controlled directly or indirectly :bya 'single coil. This feature of the invention is also capable of extended useful application. I 'do not in this patent application particularly describe and point out its'utilities and advantages, nor do I in this case make claims to it, because it is described,

illustrated, and claimed in my pending application Serial No. 692,160, filed September 29, 1898, the claims in which are to be taken as covering this case in so far as this feature is concerned.

The accompanying drawings show an embodiment of my invention.

Figure 1 is a front elevation of the controlling device for the circuit-breakers, showing the series coils and the clockwork mechan ism. Fig. 2 is a detail upon an enlarged scale, showing the escapement device carry mg the circuit operator or switch forthe reapparatus will be apparent.

Fig. 5.

n Fig. 1, A is the base of the apparatus B is the frame surrounding it, and C Care cores of electromagnets, of which D D are the coils. The particular ap aratus shown being'designed for use with a ternating currents the magnetic circuits should be laminated. E E are the armatures of the electromagnets working against the springs F F, which are made ad ustable'in the usual way, so as to determine the overload at which the apparatus will operate. Gis a rod carried in guides G G the latter of which is in this particular case formed of part of the frame of the clockwork H. .Either armature may opcrate the rod by acting upon a pin 9, passing through it. On the back of the rod (see Figs. 2 and 3) is a notch 9 A wheel I, of insulating material, is driven by the clockwork whenever the lug i is released by the upward motion of the rod, bringing the notch to register with the lug. The wheel carries a segment i, of conducting metal, which serves to complete the circuit of certain relay-coils presently to be described by means of flexible contacts, one of which, L, is always touching the wheel I, and the other of which, K, is brought against the wheel by the upward motion of the rod G through a projection g, afiixed to and moving with the rod. (See Figs. 2 and 3.) 1

Referring now to Fig. 4, the circuits of the In two of the three-phase lines are current-transformers T T, each of which is in circuit with one of the coils. D D. connected in the lines in series in the usual way, and their tripping-coils m m m are connected in a circuit'from a battery or other suitable current source N, closed on the contacts L K. It is manifest that whenever the contacts touch the segment i of the wheel I the circuit will be completed, and all of the circuit-breakers will be opened. The groups of circuit-breakers constitute in facta switch mechanism for all phases of the circuit and are controlled by the operating devices to act as a unit and break all phases at the same time.

The operation of the device as thus far described is as follows: Whenever an overload comes upon one leg of the circuit, the corresponding ,coil D D will pull down its armature and raise the rod G (see Figs. 2 and 3) until the notclrg registers with the lug i. The wheel will then revolve and the contact K will at the same time be forced against it by the upward motion of the rod, and after a determinate interval, whichniay be anything desired, depending on the speed of the v Circuit-breakers M M M are i wheel, the contacts K L will be bridged by the segment i and the tripping-coils m m, at will be energized and the circuit-breaker operated. Should, however, the overload be removed before the wheel has completed its revolution, the rod G will drop, the spring K will move away from the wheel I, and the circuit will not be completed, the lug i again bringing up against the rod G.

Referring again to Fig. 4, it will be seen that I have provided switches U U U, each in circuit with one of the coils m m m. These switches may be of simple form, inasmuch as the circuit which they operate is of only moderate potential, and I have shown each of them as consisting of a spring a, which makes contact with a block it, the spring being'moved away from the blockby the toggle of the circuit-breaker. By this arrangement whenever the circuit is open at all all of the coils are cut out, so that the circuit-breakers may be independently oper-' atcd to close their articular lines whenever desired. I have siiown the circuit-breaker trip-coils in multiple; but it would manifestly be without invention and operative to connect them in series, the change being apparent without illustration. The closing of each circuit-breaker cuts its trip-coil into circuit, so that it is at once ready to operate.

Figs. 5, 6, and 7 show the second form of the device which is referred to in my statement of invention, in which at a moderate overload the time-limit feature controls the action of the circuit-breaker, while at a second and greater overload the circuit-breaker opens immediately. I will first describe the circuits as shown in Fig. 5 and then the modified form of apparatus exemplified in Figs. 6 and 7 by which in this particular case the invention is cafried into,efl"ect.

In Fig. 5 only one of the circuit-breakers is illustrated, as the application to a number is readily apparent. In this figure the parts like those already described have th same reference-letters. The clockwork when released operates a pawl which is brought into registry with the lug on the wheel I and acts to throw a switch from contact m to contact m By tracing the circuits it will be found that current flows from the secondary. of the transformer T through the coil D and the coil m of the circuit-breaker in series, and a resistance It, which I prefer to make adjustable, is also included in multiple with the coil m and in series with the coil I). \Vhcn the switch is thrown to the other contact m, the resistance is cut out and a heavier'current can pass through the coil m, so that the circuit-breaker will be immediately opened.

Referring now to Figs. 6 and 7, the mechanical part of this form of apparatus will be understood. The wheel I carries a lugQ,

' and a bar S, affixed to the rod G, prevents the rotation of, the-wheel, the lug Q engaging with it. pivoted a bell-crank lever S, a little lost motion being allowed at s. The other end of the bell-crank lever engages with a pawl P, working against the spring 7). The pawl operates a switch-contact O, reciprocating between the fixed contacts m m of Fig. 5. It will be seen that when either of the armatures E E raises the 'rod G the wheel I rotates, and at the same time the bellcrank lever throws the pawl P into position to engage after a determinate time with the lug Q.

Of course should the overload be removed in the meantime, the armature E would release the rod and the parts return to their illustrated position; but should it persist the lug will engage with the pawl and throw the contact 0 to the'contact m thus cutting out the resistance as already described. The switch 0 will thus not be moved unless the overload persists for a sufficient length of time; but should the current in the meantime continue to rise until the second overload limit is reached the drop across the terminals of the resistance R would be so great as to ass alarge current through the coil m, and t us open the circuit-breaker. I have shown the resistance R as adjustable, because under some conditions this may be desirable. 'It is manifest that the second or higher overload limit herein referred to will be fixed by the adjustment of this resistance. The higher the resistance the less the current necessary to operate the circuit-breaker irrespective of its time-limiting device, and vice versa. Iri ordinary installations the overload limits are set once for all and in consequence a permanent resistance of suitable character will be included; but under some conditions, as where a bank of generators is to be employed, some or all of which may be put into operation, different current requirements may need to be provided for, and in this case an adjustable resistance would be employed.

What I claimas new, and desire to secure by Letters Patent of the United States, is'

1. The combination with a polyphase alternating-current circuit, of circuit-breaking devices -for breaking all phases, and means operatively related to the conductors of a portion of said phases and operative under a predetermined variation of load from normal, to actuate said circuit-breaking devices after said variation has persisted a definite time interval and operative to actuate said devices quickly variation of load.

' 2. The combination with a polyphase alternating-current 'circuit, of a circuit-breaker for each of said phases, a time-limit operating device therefor operatively related to the conductors of a portion of said phases and responsive to a predetermined Variation of load from normal, and means for operating the To the other end of the bar at s is upon a greater or excessive.

. or excessive variation of load.

- .3. The combination with & circuit-breaking device having a single trip-coil, of means for energizing said coil sufficiently to trip said circuit-breaking device after a definite time interval upon a predetermmed variation of load from normal and quicklcy upon a greater 1 or excessive variation of loa 4. In comblnation with an electrlc circuit,

a circuit-breaker therein, a trip-coil for said circui-tbreaker supplied with current from said line-circuit, and means actuated by a definite variation of load from normal for diverting a portion of the current from said coil for a definite time interval and for increasing at the end of said time interval the current flowing through the coil, whereby the breaker will be tripped either after said interval upon the occurrence of continuing light variation of load or quickly upon the occurrence of a greater or excessive load variation. 5. An electromagnet circuit-breaker comprising a trip device actuated by a single tripping-coil to cause said trip device to open the circuit upon the occurrence of certain predetermined electrical conditions, and timelimit mechanism operated independently of said trip device to energizesaid tripping-coil to cause said trip device to open the circuit after a definite time interval upon the occurrence of other predetermined electrical conditions.

6. The combination of an electromagnetic circuit-breaker, a trip device actuated by a single tripping-coil to cause said trip device to open the circuit upon the occurrence of certain predetermined electrical conditions, and time-limit mechanism operated independently of said trip device to control the energizing of said tripping-coil to actuate said trip device upon the occurrence of other .predetermined electrical conditions.

- 7. The combination of an electromagnetic circuit-breaker, a trip device therefor ar: ranged to open-the circuit upon the occurrence of certain predetermined electrical conditions, and time-limit mechanism, set in opperation upon the occurrence of other predetermmed electrical conditions to open the circuit after a definite time interval, said time-limit mechanism being independent in operation during its time interval of the electrical condition of the circuit. i

8. The combination with a polyphase'alternating-current circuit, of circuit-breaking devices for breaking all phases, a trip device therefor arranged to open the circuit upon the occurrence of certain predetermined electrical conditions therein, and time limit mechanism set in operation upon'the occurrence of other predetermined electrical conditions 1n the circuit to open the same after a definite t me interval, said time-limit mechanism being ndcpcndent in operation during its time interval of the electrical condition of .the circuit.

9. The combination with an alternatingcurrent circuit, of a tranformer and a circuitbreaker included thereln, a time-limit mechanism to actuate said breaker to open the cir-. cuit ,after a definite interval, said mechanism being independent of the electrical condition of the circuit during its time interval,

breaker included therein, a time-limit mechanism to actuate said breaker to open thecircuit after a definite interval, said mechanism being independent of the electricalcondition of the circuit during its time interval, and an electromagnetic controlling device included in the secondary circuit of the transformer and controlling the operation ofthe timelimit mechanism.

- current circuit, of atransformer and a circuit- 11. The combination with an alternatingcurrent circuit, of a transformer and acircuitbreaker included therein, means comprising a clock mechanism for controlling the operation of the circuit-breaker, and electromagnetically-actuated means included in the secondary circuit of the transformer for setting the clock mechanism inoperation.

12. In a pol hase alternatin current system, the com mation with a piurality of a1- ternating-cur-rent lines, transformers and cir-i cuit-breakers included therein, means com prising a clock mechanism for controlling the operation of said circuit-breakers, and electromagnetically-actuated means included in the secondary circuit of each transformer for settin the'clock mechanism in operation.

13. n a pol hase alternatin current system, the com mation with a plurality of alternating-current lines, of circuit-breaking means included in each of said lines, transformers included in -some-0t said lines, and means controlled by said transformers for controlling the operation of said circuitbreakers.

, 14. In a three-phase alternating-current system, the combination with circuit-breaking means included in each phase line, a transformer included in each of"two. phase lines, andv means controlled by eithertrans- I former for controlling the operation alljthe circuitbreakin means.

15. The, com ination with an alternating current circuit, ofa transformer and circuitbreaker included therein, a trip-circuitfor the circuit-breaker, time-limit mechanism to close said trip-circuit after a definite interval, said mechanism being independent of the electrical condition of the circuit during its time interval, and means governed by the transformer for controlling the time-limit mechanism.

IOO

former for controlling 16. The combination with an alternatingcurrent circuit, of a transformer and a circuit-brcaker included therein, a trip-circuit for the circuit-breaker, means comprising clock mechanism for controlling said tripcircuit, and electrom agnetically-actuated means included in the secondary circuit of the transformer for setting the clock mechanism in operation.

17 In a polyphase alternating-current system, the com ina'tion with the different phase lines, of circuit-breakers included in each of said lines; transformers included in some of said lines trip devices for the circuitbreakers, and means controlled by the current in the secondary circuit of each transthe operation of the trip devices.

The combination with an alternatingcurrent circuit, of a transformer and circuiti'll&.li6] included therein,- a trip device operativel v related to said transformer and operative to open the circuit upon the occurrence of certain predetermined electrical conditions, and time-limit mechanism operatively related to said. transformer and operative to actuate said trip device to open the circuit after a definite time interval upon the occurrence of other predetermined electrical con ditions.

19. In a polvphase alternating-current system. the combination with the different phase lines, of circuit-breakers included in each of said lines, transformers included in some only of said lines, trip devices for the circuit-breakers operatively related to said transformers and operative to open the circuit of all of said lines upon the occurrence of certain predetermined electrical conditions in anvof said transformers, and timc-limit i'nechanisni also opcrativel related to said transformers and operative to open the circuit of all of said lines after a definite time interval upon the occurrence of other predetermined electrical conditions in one of said transformers.

20. The combination of a circuit-breaker, a tripping-coil c mtrolled by an auxiliary circuit, a current--n1easuring coil controlled by the circuit which is opened and closed by the circuit-breaker, clock mechanism carrying a contact governing the tripping-circuit, and a connection between the armature of the current-measuring coil and a detent for the clock mechanism; the Whole arranged so that when the current-measuring C011 actuates its armature, the clock mechanism is releaseo and When the armature is retracted the clock is stopped. V

21. In a time-limit c1rcu1t-open1ng apparatus for a polyphase circuit, the combinain some of the polyphase circuits, a time device for governing t e tripping-circuit, and a detent for the time device controlled by the current measuring coils; the whole arranged so that upon overload the time device is released, and upon persistence of the overload for a definite time the time tripping-circuit.

22. The combination with a circuit hreaker of a tripping-coil and a current-measuring coil in series with each other, a resistance shunting the tripping-coil and in series with the current-measuring coil, a timelimit device eontrolled by the current-measuring coil, and a switch controlled by the time-limit device, for cutting out the resistance; Whereby when the timelimit.device acts to open the circuit, resistance is cut out, and the tripping-coil carries the entire current, so that on a definite overload which persists for a given time, the circuit-breaker is actuated, and upon another and greater overload causing sufficient drop in the resistance the trippingcoil is immediately actuated without regard to the time limit. '1 23; The combination of a circuit-breaker, a inagnetically-controlled operating device therefor comprising a single controlling-magnetinaetive under normal current and active under a definite. variation of current strength, and a time-limit device actuated by a less variation of current strength and operative to render said controlling-magnet active to actuate said operating device after a definite time interval and to prevent its operation if the current variation should not persist.

In Witness whereof I have hereunto set my hand this 10th day of Februar 189 EDW'ARD M. F EWL TT.

Vitnesses B. B. HULL, EDWARD WVILLIAMs, Jrv

device closes the

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