US2239829A - High voltage circuit breaker - Google Patents

Description

April 29, 1941.

R.-R. Prr'rMAN Erm. 2,239,829

HIGH VOLTAGE CIRCUXT BREAKER Filed Jan. 5, 1938 2 Sheets-Sheet 1 April 29, 1941. R. R. PITTMAN Erm. 2,239,829

HIGH VOLTAGE CIRCUIT BREAKER Filed Jan. 5, 1938 2 sheets-sheet 2 INVENTORS @a @Vm @MALI-Lm Patented Apr. 29, 1941 UNITED STATES PATENT OFFICE HIGH VOLTAGE CIRCUIT BREAKER Ralph R.. Pittman and Carroll H. Walsh, Pine Bluff, Ark.

This invention relates to high voltage circuit breakers for use in connecting and disconnecting electrical apparatus respectively to and from high voltage overhead circuits, and particularly to an automatic trip-free open type of breaker, embodying a. thermally responsive element, which is suitable for use in connecting and protecting distribution transformers connected to these circuits.

Because of the fact that heretofore no suitable circuit breaker has been available for this purpose, the high tension windings of distribution transformers have been and are now generallyy connected to overhead high voltage Icircuits through expulsion fuses. Such fuses are unsatisfactory for the reason that a new fuse element is required after each operation of the fuse, and also because the current-time curve of the fuse does not follow that of the connected transformer. Low amperage fuse links are required for this service because of the high voltage, and such links are susceptible to blowing from harmless transient currents, and are generally mechanically weak.

Present available types of circuit breakers which are satisfactory for this purpose exceed the cost of the distribution transformers in many cases, and are therefore too expensive for general use, both as to price and as to cost of mounting.

To provide a suitably inexpensive breaker of desired effectiveness, thesolution of several problems, representing the principal objects of the present invention, was necessary.

The first oi these objects is the provision in a high voltage circuit breaker of a thermally responsive element capable of relatively largemovement in response to moderate current, that is, an element which moves sufficiently to trip the breaker in response to small change in temperature.

Another object is the provision of means for preventing the tripping of the breaker due to changes in ambient temperature, since-the ther- Inally responsive element is actuated by a small change in temperature due to current therethrough.

Another object is the provision of means for shunt-circuiting the thermally responsive element when it has moved sufficiently to trip the breaker, since the element, being necessarily responsive to low currents, is liable to fusing at very highv currents.

Another object is to provide means for interrupting the circuit within an expulsion chamber or tube in response to an over-current through the breaker.

Another object is the provision of means for removing from the circuit the expulsion tube in which the circuit is interrupted, to thereby prevent damage to the tube from creepage current, and to definitely visually indicate the open position of the breaker.

'I'hese and other objects will be apparent from the following description and claims taken in connection with the accompanying drawings forming a part of this application, in which:

Fig. 1 is a side elevational view of the invention.

Fig. 2 is a side elevational view of the device without the mounting, shown partly in section.

Fig. 3 is an upper end view'of the device without the mounting.

Fig. 4 is an enlarged sectional view taken along the line IV-IV of Fig. 2.

Fig. 5 and Fig. 6 are vfragmentary views of the upper end of the removable portion of the device.

Fig. '7 is a sectional view taken along the line VII-VII of Fig. 5.

Fig. 8 is a sectional view tafken along the line VIII-VIII of Fig. 6.

Referring first to Fig. 1, the mounting of the device includes the base Il), having rigidly mounted thereon the spaced insulators II and I2. An outwardly extending weather hood I5 is secured to the outer end of the upper insulator II by means of the cap screw I6, and a connector I4 is suitably secured, as by welding, to the upper surface of the top of the weather hood I5, for the purpose of electrically 4connecting thereto a line wire I3. The upper conducting terminal I8 is pivotally mounted for rotation about the pivot II within the weather hood I5, and an upper terminal spring I9 is interposed between these members for urging the outer end of the terminal I8 in a downward direction, the extent of this downward movement being limited by the stop 89. Thel outer or forward end of the terminal I8 is provided with an enlarged downwardly extending portion for engaging and latching a cooperating contact, as will be explained later in lincre detail.

'I'he lower or load terminal 20 is rigidly secured to the outer end of the lower insulator I2, and has suitably secured thereto the connector 22, for electrically connecting the load conductor 2I to the terminal 20. The terminal 20 is substantially U-shaped, extending outwardly from the insulator I2, and at its lower outer end is provided with an integral pair of hooks, 23, 23.

The tubular insulating member, or expulsion tube of insulating material 24 is arranged to span `the terminals' Il and 2l. A metal sleeve 80 is tightly pressed over the tube 24 at its lower end, and a pair of pins 3l, 3l extend outwardly from the sleeve along a diameter, the pins 8i fitting into and being arranged for rotation in the hooks 23, 23: the metal sleeve 30 thus providing a lower removable contact lfor the tube 24. An outwardly extending metal bracket 32, securedto the sleeve 80 by means of the cap screw 83, has pivotally mounted at its outer end for rotation about the pivot 35, the metal lever 54. A portion of the lever 34 extends upwardly above the pivot 86, and a tension spring I5, having one end secured to the upwardly extending portion and the other to the bracket `82, constantly urges the lever B4 is a counter-clockwise direction about the pivot 88. The lever 54 extends to a point near the bottom of the tube 24, and is there provided with a laterally extending grooved portion 31 for en.- gaging a flexible conductor 25 which extends from the tube 24, and the thumb screw connector 88 provides means for securing the end of the conductor 25 to"the bracket l2, the yarrangement 'being such that the spring l5 is constantly biasing the conductor 25 in a direction to extract it from the tube. w

A hollow metal sleeve 25, havingA a portion thereof fitted over the upper end of the tube 24, is rigidly attached to the tube 24 by means of the pins 21 and 23, and is provided with an integral eye 3| for convenience in manipulating the device. A removable metal plug 29 is screwed through a threaded opening between the ends of they sleeve 25and so positioned as to compress the upper end of the conductor 25 between the threaded plug 23 and the metal plug 30, the latter being slidably iitted into an opening opposite the threaded plug.

At the upper end of the sleeve 25 is mounted the insulating member 33, the lower end thereof extending downwardly into the sleeve and being rigidly secured thereto by the pin 45 to tightly close the upper end of the tube 24. A metal cap 44 is fitted over the upper end of the insulating member 39 in insulatedY spaced relation with the sleeve 25, being secured thereto by 'the pin 46, and provided with the outwardly extending portion 41. At the outer end of the outwardly extending portion 41 of the cap 44 is pivotally mounted the yoke shaped up'per contact 3l, shown in Fig. 3. 'I'he two arms of the yoke, 4|, 42, extend laterally downward across the sleeve 25 and in spaced insulated relation thereto, and the stem of the yoke extends upwardly and outwardly from the pivot 43. A metal latch member 32, pivotally mounted on the sleeve 25 by means of the pivot 33, carries a pair of insulating rollers'zs, u, mounted onine pins u, u, and :ne

so positioned as to engage the upper surface of the ends of the arms of the yoke 33 'when the latch member is in a vertical podtion. Under this condition, the tube 24 is latched in the-closed position shown in Fig. 1 by the engagement. of

against the conductor 25 and the upper end of the latch member 32 in a clockwise direction.

It will be apparent from the above description that a clockwise movement of the latch member 32 about the pivot 33 will release the upper end of the conductor 25 and allow the contact 3l to move downwardly and out of engagement with` the upper terminal il,

It will also be apparent, in the arrangement described, that the upper terminal spring Il may apply a very large downward pressure against the contact 33 to assure high conductivity. without increasing the pressure of the upper end of the latch member 32 against the latch detent 11, since the downward pressure on the member 38 is transmitted about the pivot 43 through the yoke arms 4I and 42 so that the resultant force applied to the latch member 32 is in a vertical direction, and not laterally against the detent 11.

Movement of the latch member 32 is normally prevented .by the engagement of its upper end with the latchfdetent 11, the latter being rigidly secured, by means of the rivets 1 5 and 1l, Fig. 4, to the closed end of a thermally responsive element mounted at the upper end of the tube, the detent 11 being insulated from the element by means of the insulating member 12, and the insulating tubes 13 and 14. It will now be apparent that an upward movement of `the latch detent 11 due to movement of the thermally responsive element will permit a clockwise movement of the latch member 32, and result in the extraction of the conductor 25 from the tube 24, the tube and the members lattached thereto taking the open position indicated by the broken lines of Fig. 1.

'Ihe breaker being in the open position, the latch member 32, following the cooling of the bimetallic element, may again be latched against the latch detent 11, and the conductor 25 reinserted and clamped in its original position by manipulation of the threaded plug 29. By means of an insulated switch stick cooperating with the eye 3|, the tube 24 may be rotated back to the closed position. In the event a fault exists in the connected circuit, the latch member 32 is immediately unlatched, and the conductor 25 released at its upper end and extracted from the tube 24,- thus interrupting the faulty circuit. Since the eye 3l is formed as a part of the sleeve 2B, the circuit interruption cannot be prevented by manipulation of the device as described; in other words, the device is of that type commonlyY known as ftrip-free.

The thermally responsive element embodies several novel features, and its mounting and relation to the circuit are shown in Figs. 3, 4, 5, 8, '7, and 8. The element itself includes three pairs of bixnetallic -strips which bend in response to temperature change; an upper pair,l 59 and 5I, joined at their outer adjacent ends by the member 61, Fig. 4; an intermediate pair 51 andv 5l, positioned below and parallel to the upper pair and having adjacent ends thereof electrically connected and mechanically joined to the open ends of the strips 59 and 50 `through the spacers 65 and E6 by the rivets 83 and 54, respectively; and a lower pair 55 and 55, extending along and spaced from the intermediate pair, and having :their outer adjacent ends electrically connected and mechanically joined to the remaining ends of the intermediate pair through the spacers 1l and 19; the remaining adjacent ends of the lower strips being mechanically ,secured to the out- Wardly extending portion of the cap 44 by means of the screws 6I and 62, Fig. 8.

This ligure also illustrates the manner in which the strips 55 and 56 are insulated to provide an electrical circuit through the element. The upwardly extending portion 48 of the sleeve 26 supports the strip 56, and is electrically connected therewith, while the strip 55 is insulated from the portion 48 by means of the spool-shaped insulatorr 49, but electrically connected to the upper contact 38 through a. portion of the cap 44. The rivet 50 maintains the insulation in rigid assembled relation with the portion 48 to provide mechanical stability.

The electrical circuit through the breaker in the normal closed position, from the terminal I8, includes serially the contact 38, the outwardly `extending portion of the cap 44, the lower strip 55, the intermediate strip51, the upper strip 59, thence across the end portion to the upper strip 60, 'the intermediate strip 58, the lower strip 56, the portion 48 of the sleeve 26, the flexible conductor 25, and the lower contact 88.

We have found .that the zigzag arrangement of strips herein described, when mounted as disclosed herein, provides a relatively large movement at the detent 11 in response to relatively small currents, which is desirable for successful operation of the device under small currents at high voltages. an arrangement is very susceptible 'to ambient temperature change, and for this reason the incorporation in the element of some means for ambient temperature compensationis desirable.

This we have accomplished by making the interf mediate strips 51 and 58 of larger section and lower resistance than the upper and lower pairs, as shown in Fig; 7, and arranging the strips, so that, when bent due to change in temperature, the concave sides of all thestrips face in the same direction.

Fig. 6 illustrates a position of the members of the thermally responsive element when carrying normal current, and Fig. the position when carrying an over-load current. It may be noted that the intermediate strip 51, because of its comparatively low resistance, is substantially undeflected, while the deflection due to the upper and lower higher resistance strips is very apparent. It may also be observed that deflection of the intermediate strips due to rise in ambient temperature will necessitate greater deflection of the upper and lower strips to unlatch the device, thus compensating for ambient temperature.

The rate of movement of the bimetallic element, or the time required for suflicient movement to trip the breaker, is preferably slightly shorter than the time required for an overload on a connected transformer to cause thermal damage. Fuse elements now employed to connect distribution transformers must carry such overloads for a short time as do not damage the transformer, in order to prevent fusing due to short time over-loads, such as may be due to motor-starting currents. Under this condition, the transformer may be seriously damaged on small continuous over-loads which do not cause fuse blowing. Our bimetallic element, however, may be made to follow the transformer heating curve for all conditions of loading and ambient temperatures, and thus provide a much higher degree of both protection and utilization of the transformers connected through our circuit breaker.

We havealso found that such through the thermally responsive element underv given ambient temperatures, the element will Dueto the fact that high values of current are available from high voltage circuits, together with the fact that high resistance strips are embodied in the thermally responsive element, some means for preventing thermal damage from overheating by high currents is desirable in our breaker. This is accomplished by means of a pair of low resistance metal members 5| and 52, having one pair of adjacent ends electrically connected and mechanically secured respectively to the members 48 and 44, and having mounted hereon, by means .of the rivets 68 and 69, the contacts 53 and 54 at the other pair of ends, as shown in Figs. 4 and 7. The contacts 53 and 54 are positioned in the path of movement of -the conduct- 'v ing bar 61, which is rigidly secured to the outer closed end of the bimetallic element by the rivets 15 and 16, Fig. 4, the bar being insulated from the bimetallic strips by the insulating spacer 1|, and the insulating tubes 13 and 14. The relation of these elements is such that the contact bar 81 engages the contacts 53 and 54 whenever the thermally responsive element has moved sufficiently to disengage the latch member 32 from the latch detent 11, as shown in Fig. 5. rIlhe thermally responsive element is thus shunt-circuited, and undamaged by current which may pass through the breaker for the time necessary to elongate and extinguish the circuit-interrupting arc within the expulsion tube 24.

It will be apparent. from the above description that in response to a predetermined current move to disengage the latch member, and be shunt-circuited by this movement, that the conductor 25 will be extracted from the tube 24, the contact 38 will be disengaged from the terminal I8, and the circuit breaker actuated from the closed position to the open position.

Although this invention has been shown in only one form it will be evident to those skilled in the art that many other forms and modifications may be employed without departing from the spirit of this invention as described above or as set forth in the following claims.

We claim as our invention:

1. A high voltage circuit breaker comprising spaced terminals, a hollow tube of insulating material spanning said terminals and movable between closed and open positions, means including a conductor within said tube and a bimetallic element externally mounted on said tube for electrically connecting the terminals, latch means cooperating with said bimetallic element for maintaining said tube in the closed position, means biasing said tube to the open position, and means responsive to a movement of said bimetallic element for unlatching said tube, said bimetallic element embodying ambient temperature compensating means whereby said movement is substantially dependent only upon the magnitude of current therethrough.

2.'A high voltage circuit breaker comprising spaced terminals, a hollow tube of insulating material spanning said terminals and movable between closed and open positions, means including a conductor within said tube and a bimetallic element externally mounted on said tube for electrically lconnecting the terminals, latch means cooperating with said bimetallic element for maintaining said tube in the closed position, means biasing said tube to the open position, means rcleasably holding said conductor and resilient means urging the retraction of said conductor from said tube, and means responsive to a movement oi said bimetallic element for' contemporaneously unlatching said tube and releasing said conductor, said bimetallic element em-A operating with said bimetallic element -for maintaining said tube in the closed position, means `biasing said tube to the open position, and means responsive to` a movement of said bimetallic element for unlatching said tube, said bimetallic element embodying ambient temperature compensating means whereby said movement is substantially dependent only upon the magnitude of current therethrough, and means for shuntcircuiting said element in response to coitinued movement thereof in the direction to unlatch' said tube.

4. A high voltage circuit breaker comprising spaced terminals, a hollow tube of insulating material spanning said terminals and movable between closed and open positions, means including a conductor within said -tube and a bimetallic element externally mounted on said tubei'or electrically connecting the terminals, latch means cooperating with said bimetallic element for maintaining said tube in the closed position, means biasing said tube to the open position, means releasably holding said conductor and resilient means urging the retraction of said conductor from said tube, means responsive to a movement of said bimetallic element for contemporaneously unlatching said tube and releasing said conductor, said bimetallic element embodying a compensating member substantially unaffected by current and relatively greatly affected by ambient temperature,` and means'for shuntcircuiting said element in response to continued movement thereof in the direction to unlatch said tube.

5. A circuit breaker comprising spaced upper and lower terminals, a tube of insulating material having upper and lower contacts adjacent its respective ends arranged to engage and disengage said terminals, a current responsive element assoctated with said tube, resilient means biasing slid tube to the disengaged position, a conductor extending upwardly through said tube from the lower contact, resilient means urging the withdrawal of said conductor from said tube, a slidable member arranged to engage said conductor at its upper end, a detent carried by said current responsive element. a swingably movable latch member carried by said tu and engaging said detent, and common resllien means for biasing said latch member against said detent and said slidable member against said conductor.

6. A circuitbreaker comprising spaced upper and lower terminals, a tube o! insulating material having upper and lower contacts adjacent its respective ends arranged to engage and disengage said terminals, a current responsive element associated with said tube. resilient means biasing said tube to the disengaged position, a conductor extending upwardly through said tube Vfrom the lower contact, resilient means urging tl withdrawal of said conductor from said tube.

having upper and lower contacts adjacent its re-` spective ends arranged to engage and disengage said terminals, a current responsive element associated with said tube, resilient means biasing said tube to the disengaged position, a conductor extending upwardly through said tube from the lower contact, resilient means urging the withdrawal of said conductor from said tube, a slidable member arranged to engage said conductor at its upper end, a detent carried by said current responsive element, a latch member swingably mounted on said tubeand engaged with said detent. and a-spring interposed between said latch member and said plug for concurrently urging said latch member against said detent and said slidable memberagainst said conductor,

8. A circuit breaker comprising spaced upper and lower terminals, a tube of insulating material having upper and lower contacts adjacent its respective ends arranged to engage and disengage said terminals, said upper contact being pivotally movable into and out oi' engagement with said upper terminal independent oi movement of said tube. a current responsive element associated with said tube, a detent carried by said current responsive element, a swingably mounted latch member engaged with said detent, a conductor extending upwardly through said tube from the lower contact, a slidable member arranged to engage said conductor at its upper end, a common spring urging said slidable member against said conductor and said latch member against said detent, means responsive to a movement of said detent away from said latch memberior relaxing said spring, and means dependent upon said movement for concurrently withdrawing said conductor from said tube and actuating said upper contact to the disengaged position. A

9. In a circuit breaker having an open and a closed position, a thermally responsive element comprising a group of at least three bimetallic 'strips assembled in substantially parallel relationship and arranged in series circuit relation, said three strips consisting of two outside strips and one intermedtate strip, said intermediate strip having a resistance substantially less than that of said outside strips, said strips bending in re-4 sponse to the passage of current therethrough and beingarranged so that the concave sides o! said outside strips face respectively toward and away from said intermediate strip, means i'or electrically vconnecting said element in the circuit. means operable in response to a movement of said element for actuating said breaker from the closed to the open position, and means responsive to said movement for shunt-circuiting said element.

10. In a circuit breaker having an open and a closed position, a thermally responsive element comprising a series circuit arrangement o! at i least three bimetallic strips mechanically joined in zigzag relation to one another, there being two outer strips and one strip interposed therebetween, nid strips bending in resronse to passage o current theretlncugh and being so arranged that 'the concave vsides of said outer strips face respectively toward and away from said intermediete strip, means electrically connecting said element in the' circuit, means operable in response to a movement of said element for actuating said breaker from the closed to theopen position, and means responsive to said movement for shuntcircuiting said element.

1l. In a circuit breaker, a. thermally responsive element comprising a group oi at least Ithree blmetallic strips assembled in substantially parallel relationship and in series' circuit arrangement, there being two outside strips and one intermediate strip, said intermediate strip having an electrical resistance substantially less than that of each of said outside strips, said bimetallic strips bending in response to passage of current v'therethrough and being arranged sothat the concave sides of said outside strips face respectively toward and away from said intermediate strip.

l2. In a circuit breaker, -a thermally responsive element comprising a group of. at least three birnetallic strips assembled in substantially parallel relationship and in series circuit arrangement, there being two outside strips and one intermediate strip, said intermediate strip having an electrical resistancesubstantially less than that of each of said outside strips whereby the rate o of bending of said outside strips due to passage of current through said element is greater than that of said intermediate, said strips being so related to one another that the concave sides of said outside strips face respectively toward and away from said intermediate strip.

i3. In acircuit breaker. a thermally responsive element comprising three pairs of bimetallic strips assembled in substantially parallelA relationship, means for electrically connecting and mechanically joining adjacent ends of the rst pair of strips, means electrically connecting and mechanically joining adjacent ends of the second pair of strips to the other adjacent ends of said rst pair of strips; means for electrically connecting and mechanically joining adjacent ends of the third pair of strips to the other adjacent ends of said second pair of strips, means for connecting the remaining adjacent ends of said third pair of strips in series with the circuit, and means for securing said remaining ends to a support, said bimetallic strips bending'in response to passage of current therethrough and being arranged so that the concave sides of all of said strips face in the same direction.

14. In a circuit breaker, a thermally responsive element comprising three pairs of bimetallic strips assembled in substantially parallel relationship, means for electrically connecting and mechanically joining adjacent ends of the fir-st pair of strips, means electrically connecting and mechanically joining adjacent ends of .the second pair or strips to the other adjacent ends of said first pair of strips, means for electrically connecting and mechanically joining adjacent ends of the third pair of strips to the other adjacent ends of said second pair of strips, means for connecting the remaining adjacent ends of said third pair of strips in series with the circuit, and means for securing said remaining ends to a support, said bimetallic strips bending in response to current therethrough and being arranged so that the concave sides of said second pair of strips faces the convex sides of said rst pair of strips and the convex sides of said second pair of strips faces the concave sides of said third pair oi strips.

l5. In a circuit breaker, a thermally responsive element comprising three pairs of bimetalllc stripsl assembled in substantially parallel relationship, means for electrically connecting and mechanically joining adjacent ends of the first pair of strips, means electrically connecting and mechanically joining adjacent ends of the second pair of strips rto the other adjacent ends of said rst pair of strips, means for electrically connecting and mechanically joining adjacent ends oi the third pair of strips to the other adjacent ends of said second pair of strips, means for connecting the remaining adjacent ends of said third pair of strips in series with the circuit, and means for securing said remaining ends to a support, said bimetallic strips bending in response to current therethrough and being arranged so that the concave sides of said second pair of strips faces the convex sides of said rst pair of strips and the convex sides of said second pair of strips faces the concave sides of said third pair of strips, and means responsive to said bending for shuntcircuiting said element.

16. A high voltage circuit breaker comprising spaced upper and lower terminals, an upwardly extending hollow tube of insulating material spanning said terminals and movable between closed and open positions, a` conductor within said tube, a current responsive element mounted externally of said tube at the upper end thereof, means including the serial arrangement of said conductor and said current responsive element for electrically connecting said terminals when said breaker is in the closed position, and means responsive to passage of a predetermined current through said current responsive element for contemporaneously withdrawing said conductor fromv said tube at the lower end thereof and moving the upper end of said tube away from the upper terminal to the open position whereby said current responsive element is electrically isolated with respect to each of said terminals when said breaker is in the open position.

RALPH R. PI'ITMAN. CARROIL H. WALSH.

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