US2412293A - Field switch - Google Patents

Description

Dec. 10, 1946. w H sc 2 412293 FIELD SWITCH Filed June 2, 1942 SSheets-Sheet l INVENTOR. WA; 727? hf S6 F/W/f Dec.l0,j1946. H HM 2,412,293

FIELD SWITCH Filed June 2, 1942 5 Sheets-Sheet 2 Fyi INVENTOR. M01475? SCV/Y/W/i BY Z f Dec. 16, 1946. w. H. SCHYMIK FIELD SWITCH Filed June 2, 1942 5 Sheets-Sheet 5 INVENTOR. M/AA H 6 67707 Dec. 10, 1946.

w. H. SCHYMIK 2,412,293

FIELD SWITCH Filed June 2, 1942 5 Sheets-Sheet 4 INVENTOR. M/A raw /7. Saw MM Dec. 10, 1946. w, sc 2,412,293

FIELD SWITCH Filed June 2, 1942 5 Sheets-Sheet 5 Patented Dec. 10, 1946 FIELD SWITCH Walter Haines Schymik, Oreland, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a. corporation of Pennsylvania Application June 2, 1942, Serial No. 445,429

4 Claims.

My invention relates to a field switch for placing a resistance across the field winding of a motor or other similar inductive circuit when the circuit is opened and, more particularly, to a combined circuit breaker and field switch so arranged that they operate to complement each other.

During the interruption of highly inductive direct current circuits, momentary high voltages are produced, as is well known in the art, which may be sufficient to break down the motor winding and other insulations of the system. To prevent damage to the winding, it is customary to provide a bypass circuit around the winding through a resistance during the opening of the supply circuit. This resistance in the circuit reduces the momentary voltage rise in the circuit and, therefore, protects the winding of, for instance, the motor or similar inductive circuit.

In circuits of this character, it is thus necessary immediately to introduce a resistance when the motor circuit is interrupted for any reason.

An object of the present invention is to provide means for integrating a circuit breaker and field switch (for connecting the field winding across a resistance) in such manner that the two elements operate to complement each other, so that one is opened when the other is closed.

Another object of the present invention is to mount the field switch operating elements on the same panel with th circuit breaker operating elements so that they may be simultaneously placed in position.

A further object of the present invention is to mechanically interlock circuit breake and field switch operating elements so that operation of the circuit breaker results in operation of the field switch.

Still another object is the arrangement of the circuit breaker and field switch operating memner that when the truck is racked into position, both the field switch elements and the circuit breaker elements are simultaneously placed in condition for operation.

Another object of my invention is the arrangement of field switch and circuit breaker elements on a removable truck in such manner that a resistance is always connected across the field winding or similar inductive circuit when the circuit breaker is racked out of position.

Still another object is to provide a cell having a switch independent of the disconnecting contacts and which is operated to open'and closed position by the racking in and out of the truck.

These and many other objects of my invention will be apparent and, where not; apparent, pointed out in the following description and drawings, in which:

Figure 1 is a side elevation with one of the side sheets removed of a circuit breaker truck withdrawn from a stationary switchboard cell.

Figure 2 is a front view of a circuit breaker panel showing the contacts and a portion of the mechanism thereof and the field switch.

Figure 3 is a side view taken from line 3-3 of Figure 2 looking in the direction of the arrows, showing the circuit breaker panel carrying the circuit breaker and field switch elements in its operative position in the switchboard cell.

Figures 4, 5 and 6 are schematic views showing three operating positions ofthe elements of Figures 1, 2 and 3; Figure 4 showing the circuit breaker closed and field switch open; Figure 5 showing the circuit breaker open and field switch closed; and Figure 6 showing the circuit breaker and field switch operating elements racked out of the switchboard cell with an auxiliary field switch in closed position.

Figure '7 is a schematic view illustrating the; operation of the field switch.

Figure 8 is a cross-sectional view corresponding to a portion of Figure 3 and showing a modifled form of disconnect structure for my field switch.

In general, my invention contemplates inserting a resistance 85 (Figure 4) across an inductive winding 40 in response to any action which invention is the provision of means for mounting a field switch and circuit breake elements on a removable circuit breaker truck in such mandisconnects such a winding from its source of supply and just preceding such disconnection; and for cutting said resistance out of the circuit with the inductive winding immediately after said winding has been connected with its source of supply.

This action is extended to include not only operations where the inductive winding may be dis- I sulating material.

asraaoe sistance 85 is connected in circuit with the inductive winding 40 on the removal of the truck. My invention also contemplates a cell having a switch thereon and a truck which when racked into the cell disconnects the switch. In my specific embodiment, the switch normally maintains the resistance 85 across the inductance l and is operated to open this contact when the truck is racked into the cell.

Inasmuch as the main circuit breaker is always in trip position during "the racking operations, the auxiliary means which is mounted on the truck for closing the resistance circuit across the inductance is in closed position prepared to replace the switch in the cell when the truck is racked in.

Referring now to Figure 4, I have here substantially shown a circuit breaker truck 80 racked into position in engagement with the elements of a switchboard cell structure 20. The showing of Figure 4 is entirely schematic and the actual form anad exact operation of each of the elements therein shown will hereinafter be explained in connection with the description of Figures 1 to 3.

The circuit breaker and field switch operating elements are mounted on a panel ll of in- The circuit breaker l3 comprises a contact carrying arm [4 pivoted at l5 and carrying the contact bridging element 18. The bridging contact 86 may be moved to closed contact position by the operating arm H which rotates about its pivot 93 and is in toggle relation with thelink It. The circuit breaker is held in closed circuit position by the latch 23. When the latch 23 is disengaged from the operating arm I! in any suitable manner as, for instance, by the usual tripping coil (not shown) or by manual operation, the toggle li-lfi is permitted to break downwardly to the positionshown in Figure 5, thus permitting circuit breaker contact l6 to move to the left (with respect to Figures 4 and 5) and thereby disengaging the mov able contact it from the stationary contacts to and 3|.

The stationary contacts 3d and M are mounted on the front of the panel ii and are secured to back connection studs 32 and 33 which respectively terminate in disconnect contact elements 35 and 36. These disconnect contact elements 35 and 36 of the circuit breaker engage respectively with the stationary disconnect contacts 31 and 33 in the switchboard cell 25 when the circuit breaker is racked into position.

Accordingly, when the circuit breaker is in position and the movable contact l6 thereof is in engagement with its stationary contacts 30 and 3|, current for the winding 40 of the motor or dynamo ll, extending from a source of supply over conductor 9, passes through the disconnect contacts 31 and 35, back connection stud 32, the stationary circuit breaker contact 30, the movable bridging contact l5, the stationary contact 3|, the back connection stud 33 and the disconnect contacts 36 and 38 to the opposite terminal 8 of the source of supply.

Obviously, therefore, when the movable circuit breaker contact I6 is moved to its tripped or open position, as shown in Figure 3, the circuit through the field winding 40 of the dynamo or motor 4| is broken. Also, as shown in Figures 4 and 5, when the movable contact id of the circuit breaker as is moved to open position, the movable contact at or the field switch M is moved to closed circuit position.

The field switch 5! comprises an upper stationary contact 52 mounted on the circuit breaker panel H and a lower terminal connection 55 also mounted thereon.

The movable contact structure of field switch 5| includes a contact 50 mounted on a contact carrying arm 55. The contact carrying arm is connected by the lead 54 to the lower terminal 53. The contact arm 55 is pivotally mounted at 56 and is urged to a position wherein the contact surface 50 isin engagement with the stationary contact 52 by the tension spring 51 which engages the arm 53 or arm 55.

Another arm 60 mounted on the movable contact carrying arm 55 is pivotally connected'at M to the operating link 52. The opposite end of operating link 62 is provided with a slot as which engages a stud 84 on the circuit breaker operating structure. When the movable contact surface 50 is in engagement with the stationary contact 52 or the field switch 5!, then a by-pass circuit through resistance 85 exists from the field winding 40 along conductor H to stud 72, thence along conductor '83 to the stud or contact 14; the l. over the stationary lower disconnect contact 15 of the field switch to the mov able disconnect contact 18 mounted on the back connection stud ll of the circuit breaker panel; then to the contact 53 carried by the back connection stud Tl, then through the lead 54 to the contact carrying arm 55 to the contact surface 55 thereof, then through the stationary field switch contact 52 mounted on the back connection stud to the movable disconnect contact at in engagement with the stationary disconnect contact 82 to the contact stud 83, thence over conductor 84, through the resistance 85, over conductors 85 and El to the winding 45.

As has heretofore been pointed out, the link 62 interconnects the field switch contact carrying arm with the operating elements of the circuit breaker i3 so that the stud 64, when the circuit breaker is closed, engages the lower end of slot 53 to draw the link 62 in a counterclockwise direction (with respect to Figure 4) to cause the contact arm 55 also to rotate counterclock= wise to disengage contacts so and 52 of the field switch.

When the operating members ll of the circuit breaker i3are moved to the open circuit position,

as shown in Figure 5, then the stud 64 thereon,

moves upwardly. thus permitting the link 62 to move upwardly. The relaxation of the downward force exerted by the stud 54 on the slot 63 of the link 62 now permits the tension spring 51 of the field switch contact arm 55 to cause the field switch contact arm to rotate to closed circuit position.

It should here be noted that reliance is not placed on the movement of the operating arm upwardly when the circuitbreaker is open to force the link 62 upwardly to close the field switch, but rather slot 63 is of suflicient length so that the spring 51 will be able to rotate the contact 50 of the field switch to closed circuit position before the circuit breaker is entirely open.

The slot may be made of -suifiicie'nt length, in fact, so that the field switch is permitted to close at the moment that the circuit breaker movable contact begins to open but before the contacts actually separate.

The slot 5t and stud 64 are so arranged with respect to the circuit breaker tripping operation that on the instant when collapse occurs of the linkage mechanism l9, as described above, and the arm I! starts on its upward clockwise movement about its pivot 18, the pin 84 on the arm 11 moves a distance from the lowersurface of the slot 63 sufficient to permit the spring 51 to rock the contacting arm 65 clockwise about its pivot 56 into engagement with the stationary contacts 52 and 53 before the movable contacts of the switch it have disengaged their stationary contacts to and 8|.

That is to say, upon the tripping operation being initiated, the first movement which occurs in the toggle mechanisms including H and the movement of the link 552 permits a closing operation of the switch contact against the stationary contact before the toggle movement has progressed sufllciently far to disengage the contact Hi from its stationary contacts.

My invention also provides for an auxiliary field switch l5i which may be operated to connect the resistance 85 across the winding to when the circuit breaker and field switch operating elements ar entirely withdrawn from the switchboard cell.

This ensures that the resistance 35 is in parallel with the field windings so both during closing and opening operations, however these are to be effected.

For this purpose, I provide a movable bridging contact its on my auxiliary field switch tilt, he said contact being mounted in the stationary portion of the switchboard structure and being arranged for operative engagement with the contact members 83 and it.

The movable contact bridging element lbil is mounted on the contact arm I55 which is pivoted at P56 and is urged into closed contact position by the compression spring lbl. When the circuit breaker and field switch operating structure is removed from the switch board cell, then spring llil urges the movable contact i550 into bridging engagement with the contacts Ni and as and thus places the resistance 85 across the winding 4b, the circuit being from winding is over conductor ii to the stud l2, thence over conductor iii to the contact 14, over bridging contact the to contact 83, then over conductor 84 through resistance 85 and conductors 86 and 81 to the winding 40.

A rod I60 is carried by the circuit breaker panel in the manner hereinafter shown and is so arranged that when the circuit breaker truck is in operative position within the switchboard cell, as shown in Figures 4 and 5, the rod I80 engages the contact bridging element Hill to move it out of engagement with the contacts 714 and 88.

Accordingly, when the circuit breaker truck is in operative position, only the principal field switch Si is operative to connect or disconnect the resistance 85 across coil 40. When the circuit breaker truck is racked out of position, then the rod I60 is withdrawn from its engagement with the movable bridging contact I50 or the auxiliary field switch I51, and the spring I51 thereof can now urge the contact I50 into bridging engagement with contacts 14 and 83, closing the circuit in the manner above set forth. The operation and utility of the auxiliary field switch will be hereinafter set forth.

From the foregoing, it may therefore be seen (iii that the circuit breaker and field switch elements are so arranged that when the circuit breaker truck is in operative position in the switchboard structure, then:

1. The field switch 5! and the auxiliary field switch |5l will be opened when the circuit breaker contacts are closed; and

2. When the circuit breaker contacts are open, the field switch 5| will close, thus connecting resistance across the coil 40.

3. When the circuit breaker truck is removed from the cell, then auxiliary field switch i5l is closed, for purposes hereinafter set forth.

4. As is hereinafter set forth, the movable contact it of the circuit breaker is intended to open before the circuit breaker is racked out of position. Inasmuch as switch contacts 50 and are closed when the contacts of switch it are opened "efore racking out operations begin, the auxiliary field switch lei is opened.

As the circuit breaker is racked out of position, the removal of rod mil permits auxiliary field switch liii to close. The disconnect contacts ti-M and "JG-i5 are so arranged that the auxiliary field switch 65H may close before these contacts are disconnected so that resistance will always be across winding til when thecircuit breaker is intended to be open.

By this means a simple automatic method is provided for placing a resistance across the field winding of a motor or dynamo immediately upon the opening of the circuit to prevent damage owing to a momentary rise in voltage.

Since this operation is automatic and requires no separate manual manipulation, the safety factor is greatly increased. Just preceding the opening of the circuit for any cause, the resistance is automatically placed across the field winding. This is so whether the circuit breaker is opened automatically or manually. Should there be any attempt to rack out the circuit breaker, then, in addition to the means which are provided to automatically trip the circuit breaker open, an auxiliary field switch is provided to place the resistance across the field winding.

The primary purpose of the auxiliary switch i is to ensure that where the resistance 35 is utilized in connection with a number of circuit interrupters, this resistance will be in circuit to protect the field winding even though one or more of the circuit breakers may be withdrawn from its cell.

Thus, where one or more supply circuits are utilized on the same load system, each of the lines having its own circuit breaker, and where a single resistance 85 is used to protect the field winding of the load or motor; then, upon the withdrawal of one of the circuit breakers from its cell while the others remain connected, it is important that the resistance 85 nevertheless be arranged to be connected across the field upon the opening of the other circuit breakers.

Accordingly, auxiliary field switch i5l, which closes upon removal of the circuit breaker from its cell, produces this result.

This will be obvious from an examination of Figure '7 (where a slightly different auxiliary field switch 45l is shown which, however, functions in. the same manner as auxiliary field switch l5! of Figures 1 to 3).

In Figure 7, all of the elements mounted on the circuit breaker trucks Hi and I0 are the same as the elements mounted on the circuit breaker truck ID of Figures 1 to 3. The sole exception 7 is that the disconnect contacts "I, 482', 403 and 884 of the field switch 5! are sliding contacts which remain in engagement with each other over a substantially greater movement than obtains with the type of disconnect contacts utilized for the circuit breaker terminals. This will ensure that the field switch 5| will be operative to connect the resistance across the winding 48 until the auxiliary field switch til is closed. The auxiliary field switch has a difierent mechanical form (hereinafter described) than auxiliary field switch fill of Figures 1 to 3; but operates in substantially the same mannerand has an identical function. It bridges the terminals 83 and 14 when the circuit breaker truck is withdrawn from the cell.

The circuit breakers here shown are two pole circuit breakers having bridging contacts I6 and ii which are mechanically interlocked by the member 2' to operate together.

Generator m is connected through the circuit breaker mounted in truck I ll to energize the field winding 48 as follows: current flows from the generator along conductor-8 to the closed bridging contact l6, then to conductor ll; then through conductor 4 to the field winding 48 and through conductors 81 and 9 to the closed bridging contact [6, then through conductor M8 to the generator.

The current from generator I I ll also may flow through field winding 48, when the circuit breaker in truck I8 is connected and closed, over an exactly similar path.

Resistance 85 is connected across the winding 48 as follows: the connection is made from the left end of resistance 85 through conductor 84 to the contact stud 83, then through the field switch 5| or auxiliary field switch 45l (when either of these switches are closed) to the contact stud 14, then through conductor 13 to the contact stud 12, then through conductors H and 4 to the field winding; through the field winding to conductors 81, 9 and M5 to the contact stud 14, then through the field switch 5| or auxiliary field switch 45l (when either of these switches are closed) to the conductor 88 to the right end of resistance 85.

It will thus be seen that the field switches are in series; so that both must be closed to connect the resistance 85 across the winding 40.

When the circuit breakers in trucks ill and Ill are both racked in and in closed position, then current from both generators M8 and 4H! energizes the winding 40.

Should a fault occur in the line circuit from, say, generator 8 then the breaker in truck [O will be opened, thus closing the field switch 5| in the manner previously described (should the breaker in truck Ill also open, it may be reclosed). The closing of field switch 5| thus leaves the by-pass circuit through the resistance 85 in such condition that it may be closed by closing of field switch 5| should the circuit breaker in truck Ill then be tripped.

Should a fault occur in the load circuit, then both circuit breakers will be tripped and both field switches 5! will be closed thus connecting the resistance 85 across the winding.

When it is desired to rack out truck l", while at the same time it is necessary to operate the motor ll from the generator Ml), then, the auxiliary field switch 45 will bridge the contact studs 83 and 14, thus leaving the by-pass .circult in such condition that the closing of field switch (in truck l8) upon the tripping of its circuit breaker, will establish the by-pass circuit through the resistance 85.

Thus, by the use of the auxiliary field switch l5l (of Figures 1 to 3) or I (of Figure 7). the

5 removal of one of the circuit breakers from its cell will nevertheless permit the resistance 85 to protect the field winding upon the trippin of the remaining circuit breakers.

While this system has been described in connection with two circuit breakers, it isaclear that, with simple variations which should now be obvious, it may be utilized with three or more circuit breakers. It is also obvious that, while two pole circuit breakers have here been shown; the system may, with obvious adaptations, b: utilized with any single pole or multi-pole circui breakers. 1

One physical embodiment which my invention may takeis shown in Figures 1 to 3. g

In Figure 1, I have shown a circuit breaker truck Ill mounted on wheels 28!, 2| and racked out ofthe stationary switchboard cell 28. The side enclosing sheets of each of these members have been removed in order to show the operating elements.

The cell 28 comprises a framework which includes upper and lower structural members 2 and H2 on each side of the cell and vertical structural members 2l3, 2, H5 and 2l6. This framework is covered on top, bottom and sides by suitable enclosing sheets. The front of the cell 28 is closed by the front panel 211 of the a circuit breaker truck. The rear of the cell 28 is closed by the removable flanged panel 2|8.

A panel 220 of insulating material is mounted between the vertical members 2l5 and supports the male stationary disconnect contacts 31 and 38 of the circuit breaker. These members extend through the panel 220 and are provided with terminals HI and 222 for connection to an electrical circuit, which in the present instance is intended to be the field winding 40 of the motor 4| or any other similar inductive circuit.

The stationary male disconnect contacts 82 and 15 of the field switch are also mounted on the panel 228. The terminals of these contacts extend through the panel 220 and form respectively the contact studs 83 and 14 (see Figures 1 and 3).

50 Leads 84 and 13 are connected thereto to complete the resistance circuit in the manner which has already been set forth.

The contact member 83 may comprise a suitable plate of conductive material secured to the back of the panel 228, as shown particularly in Figure 3, in conductive relation with the field switch stationary disconnect contact member 82.

The member 82 may be secured by the bolt 23I to the angle member 230, which, in turn, is secured by the bolt 232 to the panel 220. A bolt 234 passing through the angle member 230, and the panel 220 may engage the plate 83, thus firmly securing it to the panel 220 and ensuring the conductive relation between the disconnect contact 82 and the contact plate 83.

The lead 84 may be connected to the contact plate 83 by a bolt 235 or in any other suitable manner.

The contact stud 14 is secured to the back of the panel 220 by being mounted on a back extension of the stationary field switch disconnect contact I5.

It is also securely supported in position by the switch brackets 248 of the auxiliary field switch operating arm hereinafter described.

The stationary disconnect contact is secured by a bolt 24! to the angle member 242 which is secured by the bolt 243 120 the front or the'panel. Bolt 2 passes through the angle member 242 and the panel 220 and terminates in a stud 245 to which the lead it! may be connected. v

In this manner the stationary disconnect contact l5 and the contact plate 74 may each be connected through the angle member 242 and the bolt 2M to the lead '83.

The circuit breaker truck lb (Figure 1) carries the circuit breaker panel ii. The back connection studs 32 and 33 of the circuit breaker are mounted on this panel to project beyond the back thereof. Stationary contact members 35 and 38 (Figure l) of the circuit breaker are mounted on the projections of these studs beyond the front of the panel it to engage with the movable bridging contact 86. The stationary contacts 3i and 3% are not shown in Figures 1, 2 and 3 but are schematically indicated in Figures 4: to 6. These, of course, may take any conventional form which will enable them to cooperate with the bridging contact i i.

The back connection studs 32 and 33 terminate in movable disconnect contact elements 35 and 35 (Figure l) which, when the circuit breaker is racked into position, engage with the male stationary disconnect contact elements 3'! and 38,

as previously described in connection with the schematic figures. 4

The field switch 5! (Figures -i, 2 and especially 3) comprises a contact carrying arm 55 which is mounted on the pivotal member 56 which, in turn, is supported by suitable brackets 25E (Figure 2) on the panel ll of the circuit breaker. llontact carrying arm 55 carries a contact member cfi'having a contacting face which is engageable with an upper stationary contact 52 and an arcing contact 260.

Upper stationary contact 52 is mounted on and operatively connected to the back connection stud til, to which is securedthe movable disconnect contact member 88,

A lead 56 connects the contact member 5d to the lower terminal 53 of the field switch, which, in turn, is secured in any suitable manner to the front end of back connection stud IT on the back end of which is mounted the movable disconnect contact 16.

The back connection studs 80 and T3 are spaced by the insulating member 262 on which is mounted the rod lSil.

The field switch 5! has a magnetic blow-out coil 263, one terminal of which is connected to the back connection stud Bil, the ot er terminal of which is connected to the plate 264 to which the arcin horn res is secured. The arcing horn carries arcing contact 260.

An are quencher 266 may be mounted in any suitable manner over the movable contacts id-El-ifib of the field switch.

Contact carrying arm 55 of the field switch has an extension 58 to which is secured one end oi. the tension spring 5'5, the other end being secured at 2m to the circuit breaker panel ii. The spring 51 tends to rotate the contact carrying arm 55 in a clockwise direction to bias the switch toward a closing position.

An arm 50 on the contact carrying arm 55 is pivoted at 6| to the operating link 62. The opposite end of the link has a slot 63 therein which is in operative engagement with the stud dd. Stud 64 is mounted on a U-shaped bracket 2T2 (Figure 2) which is secured by bolts 2'73 to the insulated bar 214 which interconnects the two poles 215, 216 of the two-pole circuit 5 breaker here shown for simultaneous operation; that is, operating elements which are connected to the members of pole 215 to operate the same will cause the elements of pole 2T8 simultaneously to operate by reason of their being united by the insulating bar 214.

The circuit breaker operating members H are so arranged that the stud 6G will move downwardly in a counter-clockwise position around the pivot i8 when the movable circuit breaker contact i6 is moved to closed circuit position.

As will now :le clear, when the toggle ll collapses on its first movement. the lug 54 is carried away from engagement with the bottom of the slot $3. This is immediately sufiicient to rock the field switch El under the action of its spring El in a clockwise direction about its pivot 56 to engage its stationary contacts 52 and 53this occurring before any opening of the main circuit breaker E3.

5 As the toggles action continues thereafter, the

- main circuit breaker i3 disengages its contacts moving to an open position and during this operation the lug dd has moved to its position at which it engages the upper inner surface of the slot 63 as shown in Figure 3, the toggle then being in its completely collapsed position.

As the toggle mechanism ii is operated in a counter-clockwise direction about its pivot t8, the lug QM moves in the slot and thus there is no effect during this first portion of the movement of the main switch. The closing operation of the main switch 23, therefore, continues to a point just before its contacts are engaged. At this point, lug cd engages the lower surface of slot '56.

As the last final locking operation on the main circuit breaker occurs, the lug 6%, in engagement now with the lower surface of slot ill, will exert a pull on the link '52 which acts through the pin St to rock the bell crank shaped field switch arm 5b about its pivot 56 in a counterclock wise direction to disengage its contacts.

Thus, operation of the field switch 55 occurs to recluse its contacts before the main circuit breaker is opened to separate these contacts just after the main circuit breaker is closed-this being effected by the free play provided for the lug 6% in the slot 63.

The closing operation may either be performed manually or by means of a solenoid operated closing device 2M (Figure l) which, by the link 282,

is connected to the operating members H.

A shunt trip 284 may also be provided for the circuit breaker connected by a link 285 to the latch 23.

The slot therefore, ensures that the field switch will not open until the circuit breaker contacts are closed, while the field switch will close just before the circuit breaker contacts are 55 fully separated during their opening movement.

The field switch 5i operates, as previously set forth in connection with the description of Figures 4 and 5, when the circuit breaker is in position in the switchboard cell.

When it is desired to rack the circuit breaker out of the switchboard, then auxiliary field switch lfii becomes operative. The circuit breaker panel it carries a tripping arm 3&8 which is engageable with the roller 30! on one of the side sheets of 75 til Ki l. structure 20 (see Figure 1). The arm aaiases 300 has a chamfered surface 302-403 communicating with the notch 304.

When the circuit breaker is in position in the cell, the roller 30f in the cell engages the notch As the racking out operation commences, the movement of thecircuit breaker, truck, which moves the arm 300 past the roller 30I, will cause the arm 800 to rotate in a counterclockwise direc=' tion with respect to Figure 1 around its pivot 305 as the roller 30I enters the chamfered surface 300. This will cause the link 305 to be moved downwardly, thus tripping the latch in the same manner as does link 285 when the shunt trip 284 is operated.

Thus, in the event that the circuit breaker has not been opened before it is racked out, it is tripped open on the initiation of the racking out operation. The engagement of roller 30I with surfaces 302 and 303 of arm 300 also serves to trip the circuit breaker open, should it be racked into position while closed.

The racking operation herein set forth is shown in Patent No. 2,237,367, assigned to the assignee of the present application.

Simultaneously, with the racking out of the circuit breaker, rod I60 is moved out of engagement with the end of the plunger 3I0. Plunger 3l0 is mounted in the panel 220 (see particularly Figures 1 and 3) and is urged into movement toward the left by the compression spring 3I I. The end of plunger 3I0 is in engagement with the adjustment nut 3I2 on the end of rod I60. The rear end of the plunger 8I0 carries a member 3, which is engageable with the plate 3, on the operating arm I55 of the auxiliary field switch I5I.

The operating arm I55 is pivoted at I56 on the brackets 240 on the rear of the panel 220 and is urged in a counterclockwise direction by the compression spring I51 which is mounted at one end in the panel 220 and at the other end bears against a pin 320 on the arm I55.

When the circuit breaker truck I is in position in the cell, the rod I60 engages the plunger M0 to push its member 3 against the plate 3I5 to rotate the arm I55 in clockwise position so that the contact I50 is out of engagement with the stationary contact members 83 and 14.

As the circuit breaker is racked out of position, the rod I60 is withdrawn, thus permitting the compression spring 3 to move the plunger 3) to the left, thereby permitting compression spring I51 to rotate the contact carrying arm I55 in counterclockwise direction.

This permits the bridging contact l50 to close on the stationary contacts 83-14, again connecting theresistance 85 across the field winding 40.

In Figure 8, I have shown a modified form of auxiliary field switch 45I which corresponds in function to the above described auxiliary field switch I I, and which already has been mentioned in connection with the description of the schematic diagram of Figure 7.

In Figure 8. the circuit breaker operates in the same manner as the circuit breaker of Figures 1 to 3 and the field switch 5I is identical with the field switch 5| of those figures. All other parts of he circuit breaker structure and its truck are identical with the parts previously described. The differences lie in the modified form of auxiliary field switch HI and its associated parts.

Th back connection studs 80 and 11 of the field switch pass through openings in the panel II and through corresponding openings in the flanges 420 and 42I of the T-shaped insulat g member 422 when their ends are secured by suitable metallic washers and bolts 424. Metallic current conducting members 425 are secured against opposite surfaces of the insulating memher 422 by the bolts 424 and by any other suitable means of securement as, for instance, the screws 425.

The ends .of the conductors 425 are bent to form retaining flanges 421.

-A spring metal conductor 480 (on each side) is secured at 43I in the end of the insulating supporting member 422; the opposite end of each conductor 430 is urged by spring 432 away from the support 422 so that the contacting faces 435 may have suitable pressure to make a good sliding contact with the disconnect contact members 440, 440. The free ends of the members-430 are restrained in their outward movement in' response to the springs 432 by the retaining flanges 421. A current carrying connection between con ductors 425 and contacts 430 is made by the pigtails 442, each secured at one end by the screws 425 and at the opposite end to thebolts 444 which guide and secure the springs 432.

The upper contact 430 is thus electrically connected to the upper connection studtll and the lower contact 430 is connected to the lower stud 11 The disconnect contacts 440 are each secured on suitable insulating supports 480 which extend from the insulating panel 45I mounted on the rear wall member 220 of the cell. The bolts 455, which secure the insulatingpanel I to the insulating panel or wall member 220, also electrically connect the ends of disconnect contacts 460 to their respective contact studs 83 and 14 The auxiliary field switch 45| is a bridging member adapted to bridge con'tactsilil and 14 Member 45I is mounted on the end of plunger 410 which passes through the opening 41 I in the panel 220 and opening 412 in panel 46L Opening 41I is provided with an inner annular ledge 413 against which one end of a compressio spring 415 bears.

The opposite end of the spring bears against the end of a sleeve 411 mounted on the plunger 410.

The spring 415 thus biases the contact member 45I toward engagement with contacts 83 and 14".

When the circuit breaker is racked into position, the end of member 422 bears against the end of plunger 410 and forces the contact 45! out of engagement with the contacts 83 and 14 When the circuit breaker is racked out, then the spring 415 is free to urge the contact member 45I into closed position thus closing the auxiliary field switch.

The length of the disconnect contacts 440 is such as to ensure that. the field switch 5i will be connected in circuit with the resistance 85 and the field winding during the racking out process at least until the auxiliary field switch 45I is closed. I

In the foregoing, I- have set forth a field switch coupled with an auxiliary field switch for connecting a resistance across the field winding of a dynamo. or in a similar inductive circuit, to protect the device against momentary rise in voltage which may occur on the breaking of the circuit.

The operation of each of the elements has been described particularly in connection with schematic Figures 4 to 6 and also in connection with Generally, the device is so arranged that when the circuit breaker opens, the field switch closes, thus connecting a resistance across the field winding. After the circuit breaker is closed, the field switch is automatically opened. The field switch and the circuit breaker are so arranged that the field switch opens after the circuit breaker is closed and so that the field switch closes before the circuit breaker is fully opened.

An auxiliary field switch is provided and is automatically operable to closed position when the circuit breaker is racked out of the switchboard cell.

All of the operations connected with the switching of a resistance in circuit across the winding of the field coil are automatic so that no additional operations, manual or otherwise, need be performed, and the equipment, as well as the operator, is fully protected.

In the foregoing, I have set forth in schematic form and in preferred embodiments various elements of my invention. Many variations and adaptations thereof should now be obvious to those skilled in the art. I, therefore. prefer to be bound not by the specific disclosure herein but only by the appended claims.

I claim:

1. A circuit breaker, a panel for carrying the same, a cell for said circuit breaker, said cell having a wall; said panel being movable toward and away from said wall; said wall carrying a switching member; means on said panel engageable with said switching member to open the same when the panel is in one position with respect to said wall and disengageable from said member to close the same when said panel is in another position; a switching member on said panel in parallel with said switching member on said wall; said switching member on said panel being closed when said circuit breaker is 14 engageable from said member to close the same when said panel is in another position; a switching member on said panel in parallel with said 7 switching member on said back wall; said switchopen; and disconnect contacts between said two ing member on said panel being closed when said circuit breaker is open; and disconect contacts between said two switching members establishing the parallel connection therebetween; said disconnect contacts being slidable contact members.

3. A circuit breaker, a panel for carying the same, a cell for said circuit breaker, said cell having a back wall; said panel being movable toward and away from said back wall; said back wall carrying a switching member; a plunger on said panel engageable with said switching member to open the same when the panel is in one position with respect to said back wall and disengageable from said member to close the same when said panel is in another position; a switching member on said panel in parallel with said switching member on said back wall; said switching member on said panel being closed when said circuit breaker is open; and disconnect contacts between said two switching members establishing the parallel connection therebetween, said disconnect contacts maintaining current carrying engagement during outward movement of said panel until said plunger is completely disengaged from the switch in the cell.

4. A circuit breaker, a panel for carrying the same, a cell for said circuit breaker, said cell having a back wall; said panel being movable toward and away from said back wall; said back wall carrying a switching member; a plunger on said panel engageable with said switching member to open the same when the panel is in one position with respect to said back wall and disengageable from said member to close the same when said panel is in another position; a switching member on said panel in parallel with said switching member on said back wall; said switching member on said panel being closed when said circuit breaker is open; and disconnect contacts between said two switching members establishing the parallel connection therebetween; an insulating support on said panel for the elements of the disconnect contacts carried thereby; said plunger being carried by said insulating support.

WALTER. HAINES SCHYMHI.

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