I.B. 35-225-1C i

RECEIVING • INSTALLATION • MAINTENANCE

De-ion®

1AIR CIRCUIT BREAKERS

Types DB-15 and DB-25

600 Volts A-C250 Volts D-C

Interrupting RatingType DB-25

25/000 AmperesType DB-15

15,000 Amperes

Rating of Series CoilsType DB-25(Amperes)

40, 50, 70,90,100,125,150, 175, 200, 225, 250,300, 350, 400, 500, 600

Type DB-15(Amperes)

15, 20, 30, 40, 50,70, 90, 100, 125,150, 175, 200, 225

WESTINGHOUSE ELECTRIC CORPORATIONSWITCHGEAR DIVISION

EAST PITTSBURGH, PA.NOVEMBER, 1954

Printed la U.S.A.

EAST PITTSBURGH PLANTSUPERSEDES 1.8. 35-225-1B '

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I•=?TABLE OF CONTENTS •"

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RECEIVING, HANDLING AND STORING LPage 7Part OneInspectionStoring . . .

77

INSTALLATION Pages 8-11Part TwoConnectionsEnclosures . .

88

MAINTENANCE Pages 12-32Part ThreePole Unit

Contacts.Maintenance of Contacts

Operating MechanismClosing SolenoidOvercurrent Tripping Device

ConstructionInstallation and RemovalTime Current ClassificationOperationAdjustment of SettingsReplacing Overcurrent Devices . . . .

Control RelayShunt Trip AttachmentUndervoltage Trip AttachmentUndervoltage Time Delay AttachmentReverse Current Trip Attachment . . . .Field Discharge SwitchAuxiliary SwitchAlarm Switch AttachmentElectric Lockout AttachmentKey Interlock AttachmentTerminal Block

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{12141414151521212123242626292930303232

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I.B. 35-225-1C“DB” AIR CIRCUIT BREAKERS

LIST OF ILLUSTRATIONSPageFigure

1 Type "DB" Air Circuit Breaker—Exploded View2 Ventilated Enclosures—-Outline Dimensions and Mounting Details 93 DB-25 Outline Dimensions and Mounting Details4 DB-15 Outline Dimensions and Mounting Details5 Cross-Sectional View of Type DB-25 Circuit Breaker6 Overcurrent Tripping Device—Location .6A Overcurrent Tripping Device—Construction Details7 Tripping Characteristics of DB-15 and DB-25 Overcurrent Tripping

Devices with Long Time Delay and Instantaneous Elements7A Tripping Characteristics DB-15 and DB-25 Dual Selective Over-

current Tripping Device for Group and Tie Breakers7B Time-Current Characteristics of DB-25 Circuit Breakers Equipped

with Typical Overcurrent Tripping Devices for Motor Starting andSelective Operation

7C Schematic Diagram—Dual Overcurrents Series Tripping DeviceDB-15 and DB-25 Load Circuit Breakers

7D Schematic Diagram—Dual Overcurrent Series Tripping DeviceDB-15 and DB-25 Group or Tie Circuit Breakers

8 Typical Wiring Diagrams—Type "DB" Circuit Breaker9 Control Relay—Location, Adjustment, and Construction Details

10 Shunt Trip Attachment—Location and Construction Details. . . . . . ..11 Undervoltage Trip Attachment—Location and Construction Details .12 Undervoltage Time Delay Attachment—Location12A Undervoltage Time Delay Attachment—Construction Details13 Reverse Current Trip Attachment—Location13A Reverse Current Trip Attachment—Construction Details14 Field Discharge Switch—Location and Construction Details15 Auxiliary Switch—Location15A Auxiliary Switch—Construction Details16 Alarm Switch Attachment—Location16A Alarm Switch Attachment—Construction Details17 Electric Lockout Attachment—Location and Construction Details . . .18 Key Interlock Attachment—Location and Construction Details19 Terminal Block Attachment—Construction Details

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I.B. 35-225-1C< 4DB” AIR CIRCUIT BREAKERS

WestinghouseTYPE "DB" AIR CIRCUIT BREAKER

Type "DB" air circuit breaker is designed to give continuous and reliableservice as the protective link between the power source and associated pro-ductive equipment. This breaker is built to operate with a minimum of main-tenance, while at the same time its simplified construction permits maximumaccessibility for inspection and adjustment when required. The ease with whichattachments may be added or removed is an outstanding feature of the "DB"design.

For the greatest measure of safety to operating personnel and also to min-imize maintenance requirements, the breaker should be mounted in an enclosuresuitable to local operating conditions. A selection of standard enclosures isavailable for various applications.

Important:To assure proper functioning, inspect each breaker at reg-ular intervals in accordance with a systematic maintenance schedule.The frequency and character of the inspections will for the most partbe determined by the severity of the duty performed. The minimumrequirements, however, should consist of a light monthly inspection,with a thorough inspection semi-annually. Occasional checks on cali-bration as well as on coordination and freedom of all moving parts,must be included in the maintenance schedule. Consult Westinghouseengineering and service personnel for recommendations pertaining tospecial operating or maintenance conditions.

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FIG. 1. Type “DB” Air Circuit Breaker—Exploded View

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!TI.B. 35-225-1C

“DB” AIR CIRCUIT BREAKERSPART ONE•• \

RECEIVING, HANDLING AND STORINGa. Observe whether all parts are in proper

alignment and move freely.Type "DB” air circuit breakers, with all attach-ments mounted in place, are shipped in woodencrates or cardboard containers.

Important: To avoid damage to the break-ers, do not use hooks in handling.

Net weights of Types DB-15 and DB-25 fixedbreakers are given in Table No. 1 below. Add 15lbs. for drawout breakers.

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b. Make certain that the studs have not beenforced out of alignment.

c. Be sure that the contacts are clean andproperly aligned. For a description of contact align-ment, refer to "Contacts”, page 12.

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3. If the contacts are in alignment and all partsmove freely, continue the clockwise rotation untilthe breaker is latched.

Table No. I. NET WEIGHTS

DB-15 DB-25TYPE 4. Return the manual operating handle to the

neutral position, then rotate counterclockwise totrip the breaker.

3- Pole2-Pole 2- Pole 3-Pole

60 lbs.75 lbs. 70 lbs.

85 lbs.80 lbs.

100 lbs. 90 lbs.110 lbs.Manual

Electrica. The toggle linkage should collapse and the

moving contact assembly move freely to the fullopen position. This should be followed immediate-ly by complete resetting of the links in the togglemechanism as the handle is returned to the neutralposition.

Immediately upon receipt, examine the shipmentfor any loss or damage incurred during transit. Ifinjury or rough handling is evident, file a damageclaim at once with the transportation company andnotify the nearest Westinghouse Sales Office.

When unpacking, be sure that no loose parts aremissing or left in the packing material. Report allshortages at once. Blow out any dust or particlesof packing material that may have accumulated onthe circuit breaker parts. Remove tape from top ofarc chutes.

b. The links must always be free to movewithout friction or binding.

S. Check the attachments for operation in accord-ance with the appropriate instructions as givenunder "Maintenance”, Part Three of this book.

6. The latchplate felt and roller lever of the oper-ating mechanism should be lubricated approxi-mately every 10,000 operations. Molybdenum disul-fide mixed with oil (Westinghouse oil M8577-11) isrecommended.

INSPECTIONThe "DB” breaker assembly consists of a coor-

dinated group of sub-assemblies mounted on a steelsupporting panel. (See Fig.1). The complete break-er assembly is to be mounted with the steel panelin a vertical position. All inspections for properoperation should, therefore, be made with the break-er in this position. Final inspection should prefer-ably be made with the breaker in its permanentmounting.

Inspect the breaker as follows:1. Raise and lower the trip bar by hand to make

sure that it does not bind.2. Rotate the manual operating handle slowly in

a clockwise direction to move the contacts towardthe closed position.

STORING

If circuit breakers are not to be installed in theirpermanent location at once, they should be care-fully inspected for loose or damaged parts and thenstored in a clean dry place in an upright positionto avoid damage to the circuit breaker parts. Acovering of paper will prevent dust from settling onthe circuit breaker parts and is preferred to packingor other materials that are apt to absorb moisture.

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PART TWOr

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INSTALLATIONthat the mounting dimensions differ and should beobtained from the appropriate outline drawing.Type"DB" circuit breakers are furnished as com-

plete unit assemblies and the installation consists(1) bolting them to the supporting framework

or structure; (2) connecting the current-carrying

cables or bus bars; and (3) completing any second-ary control wiring that may be necessary.

Caution: During installation, the circuitbreaker should be in the open position. Besure to de-energize the load and control leadsto be connected, and also the section of theswitchboard where the installation is beingmade.

Mounting dimensions and details of front enclo-sure cutouts are shown in Figs. 2, 3 and 4,

To prevent distortion of the breaker panel, thesupporting structure should be checked for align-ment.

of: The following procedure applies to all enclosures:

l m Connect the entrance cables first. Wheneverpossible, the power cables should be connected tothe top terminals to remove voltage from the over-current attachments when the breaker is open. Thecables can be connected to the nearest terminal, orto the opposite terminal as shown in Fig. 2. Tinthe ends of the cable to prevent the formation ofcopper oxide. Tighten the clamp bolt securely andlock with the lock nut.

2. Control wires should run along the left sideof the enclosure below the rail. Connect to theterminal block or auxiliary switch by running be-tween the breaker platform and the rail in front ofthe wheel, after the breaker is bolted in place. Whenremoving the breaker, disconnect the control wiringfrom the terminal block or auxiliary switch and layin the bottom of the enclosure, out of the way of thebreaker.

CONNECTIONS

Typical circuit breaker wiring diagrams areshown in Fig. 8. The connecting cables or bus barsshould have adequate current-carrying capacity,otherwise, heat will be conducted to the circuitbreaker resulting in possible excessive temperaturerise. Connecting cables or bus bars must be sup-ported so that the circuit breaker studs will not besubjected to unnecessary stresses.

The circuit breaker studs and all connectionsshould be clean, smooth, and free from burrs toassure full contact area. They should be firmlyclamped or bolted in place to prevent excessiveheating.

3. Roll the breaker into the enclosure until thefour mounting bolts engage the mounting brackets.The mounting bolts are used as jacks to pry thefinger clusters into engagement with the terminals,and consequently each bolt should be tightened *4inch in succession until the breaker panel is tightagainst the mounting brackets. The same procedureshould be followed in removing the breaker, i.e.,remove each bolt % inch in succession until theydrop free.

4- Always rotate the operating handle to thetripped position before removing the front cover. Atrip rod (not shown in Fig. 2) holds the breaker tripfree when the front cover is off. When operatingthe breaker in the test position (front wheels engag-ing the slot in the rail), it is unnecessary to hold thisrod in manually to secure closure of the breaker.When fastening the cover in place, draw the fourcover bolts down firmly.

ENCLOSURES

The terminal panel and breaker arrangementshown in Fig. 2 apply specifically to ventilatedenclosures. The same arrangement is used for allother enclosures (weatherproof, subway, explosion-proof, dust tight and semi-dust tight) except

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I.B. 35-225-1CINSTALLATION“DB” AIR CIRCUIT BREAKERS

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FIG. 2. Ventilated Enclosures—Outline Dimensions and Mounting Details

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INSTALLATION,

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F R O N T V I E W O F S T U D L O C A T I O N,C U T O U T S D R I L L I N G F O R M O U N T-I N G 2 - P O L E B R E A K E R W I T H 2O V E R C U R R E N T T R I P S S R E V E R S EC U R R E N T T R I P. .(F O R D I M S. S E E V I E W A )

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FIG. 3. DB-25 Outline Dimensions and Mounting Details

I.B. 35-225-1CINSTALLATION,“DB” AIR CIRCUIT BREAKERS

FIG, 4. DB-15 Outline Dimensions and Mounting Details

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PART THREE

MAINTENANCEPOLE UNIT Maintenance of Contacts. Rough or high

spots should be removed with a file or sandpaper.To replace the arcing contacts, open the breaker,remove the arc chutes and then the stationary arc-ing contacts. Close the breaker and remove themoving arcing contacts. The new contacts can thenbe added in the reverse order.

Caution: All power should be removed whenchanging, maintaining or adjusting contacts.

Each pole unit is mounted on a separate moldedbase through which the breaker studs pass. (SeeFig, 6). The molded bases are attached to the steelmounting panel and provide insulation for the break-er studs.

The upper stud and contact are attached to themolded base by one bolt. The moving contact ispivoted on the molded base and attached to thecross bar through insulating links. The series coiland lower stud are fastened to the molded base bythree bolts.

Contacts. (See Fig. 6). The DB-25 arcing con-tacts should touch first on closing, open last onopening, and have approximately a %2-inch gapwhen the breaker is completely closed. This gapis adjusted by removing the cross bar and screwingthe insulating link in or out on the stud. Be sure totighten the lock nuts after each adjustment.

The DB-15 contacts are adjusted to obtain %2 tol/a inch gap between the armature plate and thesteel link. As the contacts burn away it will benecessaryto adjust as described abovefor the DB-25.

Do not over-adjust as this will cause the openingspring to compress to the solid position and thusincrease the closing effort. Check for over-adjust-ment by manually pulling the moving contact awayfrom the stationary contact, with the breaker in theclosed position. It should be possible to obtain atleast %4-inch gap between contacts.

OPERATING MECHANISMThe operating mechanism (see Fig. 6) is non-

adjustable and consists of a series of stainless steellinks designed to secure low closing and trippingforces. To check for friction, raise the trip bar andslowly rotate the manual operating handle in closeand trip direction. The linkage should follow thehandle without sticking.

The tripping load should not exceed 38 ouncesmeasured at the trip bar.

CLOSING SOLENOIDThe closing solenoid (see Fig. 6) is non-adjustable.

It is designed for intermittent duty only. Check forloose bolts.

The minimum permissible control voltages at theterminal of the closing coil, and the closing currentsat nominal voltage are listed in Table No. 2 below.

mTable No. 2. CLOSING SOLENOID CONTROL VOLTAGES AND CLOSING CURRENTS

MINIMUM VOLTAGEAT COIL TERMINALS

CLOSING CURRENT IN AMPERES AT NOMINALVOLTAGE FOR 3-POLE BREAKERS

NOMINALVOLTAGE 0DB-25 CloseDB-15

CloseDB-15 and DB-25Close Trip

TripSpecialStandard

1812 V, D-C24 V, D-C48 V, D-C

125 V, D-C250 V, D-C115 V, 60 Cy230 V, 60 Cy460 V, 60 Cy

714 9.528 5

90 70 20 25 30 2180 140 10 12 15 1

195190 190 30 35 49 .5380 380 15 20 24 .2

* NOTE: For A-C closing use 3-kva source or larger.0 Standard close coils used when overcurrent tripping devices have instantaneous trip.

Special close coils used when overcurrent tripping devices have short delay feature.

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I.B. 35-225-JCMAINTENANCE\

“DB” AIR CIRCUIT BREAKERSV

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FIG. 6. Cross-Sectional View of Type DB-25 Circuit Breaker

MAINTENANCE

Construction. The overcurrent tripping deviceis of the air delayed type with all elements adjust-able. The adjustment knobs or parts likely to betouched while making adjustments of time or pickupcurrent are electrically insulated. Fig. 6A showsa typical overcurrent tripping device ready formounting on a breaker pole unit.

Installation and Removal. To install an over-current tripping device, first make sure the lowerend of the flexible conductor is in the recessedpocket of the molded base directly above the lowerbreaker stud. Then place the trip unit so that thetop terminal of the tripping device is over theflexible conductor and the lower tripping deviceterminal is over the lower breaker stud. Insert thethree bolts into the rear of the base and threadthem tightly into the terminals and molded base ofthe tripping device. The mounting bolt sizes areshown in Table No. 3.

Table No. 3. MOUNTING BOLT SIZES

DB-25BOLT DB-15

Thread LengthI/2-13 X 2&*

54-13*194'%-16 x 1%"

Thread Length!/2-13 x li/2"/2-13 X V3/6-16 X r

TopCenterBottom

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FIG. 6. Overcurrent Tripping Device—Location

Use one lock washer only, under the head ofeach of these bolts. Care should be taken to makesure that bolts longer than called for above are notused, otherwise, the ends of the bolts may jamagainst the coil and short circuit some of the turns.

To adjust the trip nut for proper tripping, firstinsert valve lever tool "B" or a Vie diameter rod,in the long delay calibration bracket (left slot) andraise the valve lever to its maximum position. Thisremoves all of the time delay and permits the arma-ture to operate easily. Then insert the push rod"A" Fig. 6A in the top slot of the calibrationbracket and push the armature solidly against theyoke; close the breaker and adjust the trip nut tobarely trip the breaker. Several trials may benecessary. Next turn the trip nut upwards threequarters turn to provide overtravel. This completesthe adjustment as the trip nut is self locking.

To remove an overcurrent tripping device fromthe breaker, remove the three bolts, which hold thetripping device to the breaker base. Before re-moving the last bolt, hold the tripping device toprevent it from falling.

OVERCURRENT TRIPPING DEVICE

The overcurrent tripping devices of the variousampere ratings are of the same general constructionand size. They can be applied to the DB-15 circuitbreaker in ratings of 15 to 225 amperes and to theDB-25 circuit breaker in ratings of 40 to 600amperes.

The overcurrent tripping device can easily beremoved from the breaker and replaced with anotherunit of different rating without affecting the cali-bration.

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The overcurrent tripping device, normally fur-nished for each pole of the circuit breaker, is de-signed for service on motor or general purposefeeder circuits or for service on systems whereselective overcurrent tripping is desired. Figures7A and 7B shows time-current characteristics ofDB-15 and DB-25, circuit breakers equipped withtypical overcurrent tripping devices, for selectivetripping.

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I.B. 35-225-1CMAINTENANCE“DB” AIR CIRCUIT BREAKERS

2—Dual Selective Overcurrent Tripping Devicefor Group or Tie Breakers

This device has an adjustable long delay andadjustable short delay element and is suitable forservice on systems where selective overcurrent trip-ping is desired. Curves 7A and 7B show the time-current characteristics of these devices.

Time-Current Classification. The overcur-rent tripping device can be furnished with eithera short delay or an instantaneous element, or inany combination of two of the three tripping ele-ments, namely long delay, short delay and instan-taneous elements. The most popular overcurrenttripping devices are listed below:

1—Dual Overcurrent Tripping Device for LoadBreakers

This device has an adjustable long delay and anadjustable instantaneous element and is suitable forservice on motor or general purpose feeder circuits.A characteristic curve is shown in Fig. 7.

Operation

1—Dual Overcurrent Tripping Device for LoadBreakers, Fig. 7C

Overload currents above the setting of the longdelay pick-up adjustment (M) forces the armature

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FIG. 6A. Overcurrent Tripping Devia Construction Details

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FIG. 7. Typical Tripping Characteristics of DB-15 and DB-25 Overcurrent Tripping Devices with Long Time Delayand Instantaneous Elements

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V.B. 35-225-CMAINTENANCE“DB” AIR CIRCUIT BREAKERS

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FIG. 7A. Typical Tripping Characteristics DB-15 and DB-25 Dual Selective Overcurrent Tripping Device £orGroup and Tie Breakers.

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Typical Time-current Characteristics o£ DB-25 Circuit Breakers Equipped with Typical OvercurrentTripping Devices for Motor Starting and Selective OperationFIG. 7B.

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LB. 35-225-1CMAINTENANCE,< 4 DB” AIR CIRCUIT BREAKERS

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FIG. 7C. Schematic Diagram—Dual Overcurrent Series Tripping Device DB-15 and DB-25 Load Circuit Breakers

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FIG. 7D. Schematic Diagram-—Dual Selective Overcurrent Series Tripping Device DB-15 and DB-25 Groupor Tie Circuit Breakers

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I.B. 35-225-10MAINTENANCE,“DB” AIR CIRCUIT BREAKERS

(B) and the trip saddle (H) towards the trip bar ofthe circuit breaker. This upward movement of thearmature (B) and diaphragm (E) reduces the pres-sure in chamber (G) causing air to be sucked inthrough the timing valve (I). The rate of travelof the trip saddle (H) is determined by the rate atwhich air is permitted to enter chamber (G) byvalve (I). The reset valve (J) allows quick reset ofthe parts after the breaker has been tripped.

Short circuit currents above the setting of theinstantaneous element as determined by adjustment(N) causes the secondary armature (D) to be at-tracted to the main armature (B). The upwardmovement of secondary armature (D) moves valve(I) to wide open position, which removes restrainton the movement of armature (B). The main arma-ture (B) and trip saddle (H) move instantly to tripthe breaker.

2. Remove the lower studs and redrill the over-current bolt holes to (the bushing on thelower coil terminal must fit inside this hole). Re-place when redrilled.

3. Loosen the three bolts holding the left andcenter pole units to the panel and remove anddiscard the present barriers (3P. breakers only).Install the new barriers. The new barriers are notsymmetrical and consequently they cannot both beslipped under the center pole unit as was the casewith the existing barriers. The DB-25 barriersS#1736180 should be assembled with bumperblocks downwards; this requires one barrier to beslipped under the left pole unit and the other underthe center pole unit. The DB-15 barriers Sfit 1736179should be assembled with the beveled corners up-wards, by following the above procedure.

4- Remove the operating mechanism from theplatform and (a) remove and discard the moldedtrip fingers from the trip bar; (b) remove and dis-card the brass counterbalance from the bottom ofthe trip lever. Remount the operating mechanism.

5. If the breaker is equipped with a shunt tripattachment, remove and discard the trip lever fromthe shunt trip and replace with trip lever S#1736189.

6- If the breaker is equipped with an electric lock-out attachment remove and discard the f/ie thickMicarta angle screwed to the electric lockout lift-ing plate. Insulation is not required with the in-sulated overcurrent device.

7- Loosen the control relay and solenoid mount-ing bolts on DB-15 breakers (if supplied) and tiltforwards slightly to permit easy installation of thenew overcurrents.' Tighten all bolts after mountingthe overcurrent device.

The relay release arm (see Fig. 9) should bemaintained in adjustment to release the relay con-tacts when the release lever is approximately ^inch from its stop surface on the relay mold, withthe breaker closed.

2—Dual Selective Overcurrent Tripping Devicefor Group and Tie Breakers, Fig. 7D

The operation of this selective device is the asmeas the dual overcurrent tripping device, except,that in this case, the long delay and instantaneousvalve (I) in Figure 7C is replaced with a long delayand short delay valve (I) Figure 7D, which operatesthe same, except, when valve (I) Figure 7D isforced down by the secondary valve on fault cur-rents it controls the size of orifice to give the trip-ping time required in the fault current short delayregion.

Adjustment of Settings

Caution: As a safety measure, the breakershould be disconnected from the circuit beforemaking any adjustment.

By turning the adjustment knobs K-M-N Fig, 7Cand K-L-M-N Fig. 7D, the settings of the varioustime and pick-up elements can be changed. Aclockwise movement of any one of the knobs willincrease the setting and a counterclockwise move-ment will decrease the setting.

REPLACING OVERCURRENT DEVICES CONTROL RELAYInstruction for Replacing Sealed Oil Overcurrent

Devices by Air Overcurrent Devices. Items 1 and4 only are required for breakers shipped afterMarch 1, 1954.

1.Remove the sealed oil overcurrent and discardthe mounting bolts. The proper bolts for the in-sulated overcurrent are given in Table fit 3.

The control relay mounts directly under the aux-iliary switch (see Fig. 9). It is a single-coil, mechan-ically-tripped device with the coil suitable for con-tinuous energization. The operation sequence isoutlined in Fig. 4, page 11. The contacts shouldnormally last the life of the breaker, but are replace-able if found necessary.

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INSTALLATION,

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OPERATION SEQUENCEI. CONTROL SW. CS- C CLOSED.

^ "X" RELAY PICKS UP 8 SEALS IN THRU AUX .CONTACT " X ".

3. CLOSING COIL ENERGIZED THRU MXH CON-TACT CLOSING BREAKER.

4. IN CLOSING BKR. CLOSING MECH. MECHANIC-ALLY TRIPS "X" CONTACTS FREE OF MX" COIL,INTERRUPTING CLOSING CIRCUITS.

5. WITH BKR. IN CLOSED POSITION, THE BKR.CLOSING MECH. IS LATCHED UP AND "X" CON-TACTS REMAIN TRIP FREE FROM "X" COIL.

6. WHEN BKR. IS TRIPPED, CLOSING MECH.DROPS, PERMITTING "X " CONTACTS TO RE-SET PROVIDED '* XM COIL IS DEENERGIZED.

REVERSE CURRENTP

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SCHEMATICWIRING DIAGRAM (FV. )

UNDERVOLTAGE

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FUSE* U-Ju iCS* iCS ITCTO 8 POINT- . rt-TERM. BLK . [U785MiREAR CONN.4fSX8C 8Y 8TOFT BLK. 1

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SCHEMATICELEC. RESET ALARM SWITCH

LEGEND A- ALARM CONTACTDOES NOT CLOSEWHEN BREAKER ISTRIPPED MANUALLY

X- CONTROL RELAYCC- CLOSING COILTC- TRIP COILCS- CONTROL SWITCH

R- RED LAMP (CLOSED) TRIPG- GREEN LAMP (OPEN)

UV- UNDER VOLTAGELO-LOCKOUTB A- ALARM SWITCH

O-MAKE CONTACTb- BREAK CONTACT

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FIG. 8. Typical Wiring Diagrams—Type "DB” Circuit Breaker

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I.B. 35-225-1CMAINTENANCE,“DB” AIR CIRCUIT BREAKERS

FIG. 9. Control Relay—Location, Adjustment, and Construction Details

Check for correct adjustment by energizing therelay coil with the breaker in the closed position.If the relay contacts touch momentarily, and drawan arc, bend the release arm upward with a pairof pliers. After bending, make sure the verticalportion of the release arm does not rub either therelay mold or the solenoid frame.

SHUNT TRIP ATTACHMENTThe shunt trip mounts on top of the platform

immediately to the right of the operating mecha-nism. (See Fig, 10).

It is non-adjustable and is intended for intermit-tent duty only. The shunt trip circuit must alwaysbe opened by an auxiliary switch contact. Trippingcurrents are tabulated in Table No. 2, page 12,

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MAINTENANCE,

FIG. 10. Shunt Trip Attachment—Location and Construction Details

Inspection. With the breaker in the open po-sition, manually push the moving core against thestationary core and rotate the breaker handle to theclosed position. The breaker should be trip tree.

the reset lever spring overcomes the magnetic at-traction of the cores and rotates the reset leverclockwise. As the reset lever rotates, a pin pushesagainst the latch to release it from its latch plate.When the latch releases, the trip spring rotates thetrip lever counterclockwise to trip the breaker. Thelinkage is reset by the cross bar as the breaker opens.Fig. 11 shows the cross bar in the open position ofthe breaker.

The self-locking screw in the moving core isset at the factory and should not require adjust-ment. It is used to secure a few thousandths clear-ance at point "B", between the latch and the latchshock pin, when the moving core is held tightlyagainst the stationary core. This adjustment pre-vents faulty operations due to shocks and jars.

Always connect the coil to the line side of thebreaker unless the attachment is equipped with atime delay device. In this case, the time delay willdelay the tripping of the breaker long enough topermit energization of the undervoltage coil fromthe load side. Do not use an auxiliary switch contactin the undervoltage circuit.

The trip lever of the shunt trip should have ap-proximately a lA6-inch clearance to the trip bar.

Maintenance. Check for loose bolts and faultycoils.

UNDERVOLTAGE TRIP ATTACHMENT

The undervoltage trip mounts on top of the plat-form, to the right of the shunt trip. (See Fig. 11).Its function is to trip the breaker when the voltagefalls to between 30 to 60 percent of normal. Turnthe reset lever screw in flush with the top of thenut for instantaneous undervoltage attachments, andall the way out when a time delay attachment isadded.

The moving core is normally held magneticallyagainst the stationary core to hold the Micarta rodand consequently the reset lever, in the reset posi-tion. When the coil voltage is reduced sufficiently,

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I.B. 35-225-1CMAINTENANCE“DB” AIR CIRCUIT BREAKERS

FIG. 11. Undervoltage Trip Attachment—Location and Construction Details

MAINTENANCE

UNDERVOLTAGE TIME DELAYATTACHMENT

The undervoltage air dashpot time delay attach-ment mounts on the front of the undervoltage trip,replacing the moving core cover.The needle valve screw in the top regulates theopening through which the air is forced and con-sequently the time delay. (See Fig. 12A). Theattachment does not have a quick reset feature andtherefore approximately one minute should be al-lowed between operations to permit complete re-setting. It is set to trip within 4 to 7 seconds.

Inspection. Hold the trip bar down and closethe breaker manually. Release the trip bar slowly,allowing the undervoltage trip spring to raise thetxip bar and trip the breaker.

Maintenance. Check for loose bolts and faulty

(See Fig. 12).

coils.REVERSE CURRENT TRIP

ATTACHMENTThis attachment mounts directly on the center

molded pole unit base, in the space ordinarily oc-cupied by the overcurrent attachment. (See Figs.13and 13A). It is used to trip the breaker when thedirection of current flow in that pole is reversed.FIG. 12. Undervoltage Time Delay

Attachment—Location

FIG. 12A. Undervoltage Time Delay Attachment—Construction Details

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LB. 35-225-1CMAINTENANCE, “DB” AIR CIRCUIT BREAKERS

When the series coil current is flowing in the for-ward direction, armature movement is prevented bya stop. When the series coil current is reversed,the armature rotates in the opposite direction totrip the breaker. Calibration adjustment covers 5to 25 percent reverse current, based on normalcurrent rating.

After tripping, the reverse current armature isreset by opening the potential coil circuit. For thispurpose an "a" contact of the breaker auxiliaryswitch should be connected in series with the poten-tial coil.

Inspection. Close the breaker manually, andpush backward on the spring stud located on thebottom of the armature, to trip the breaker. Thearmature should move without friction, and shouldhave approximately %2-inch overtravel after trip-

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ping.Final inspection should be made electrically, after

the circuit connections are complete as shown inFig. 8, page 22.

Maintenance. Remove all power from thebreaker and repeat the mechanical inspection givenabove. Check for loose bolts and open circuit inpotential coil.FIG. 13. Reverse Current Trip

Attachment—Location

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FIG. 13A. Reverse Current Trip Attachment—Construction Details

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MAINTENANCE,

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FIG. 14. Field Discharge Switch—Location and Construction Details

I.B. 35-225-1CMAINTENANCE,“DB" AIR CIRCUIT BREAKERS

Inspection. Remove the arc chute, close thebreaker manually and check for freedom of motion.The break distance is adjusted by loosening the locknut and turning the sleeve in or out. Always leavea slight gap at the stop surface.

Maintenance. Remove power from the break-er, clean the contacts if necessary, check the contactseparation and adjust if necessary. Check for loosebolts.

FIELD DISCHARGE SWITCHThe field discharge switch is ordinarily used

with a two-pole breaker, and mounts on the centermoulded pole unit base. (See Fig. 14). The switchis shipped with the gap setting shown in Fig. 14,for generator field protection. However, the gapsetting can be reduced to zero or set to open afterthe breaker contacts close, if desired. An arc chuteis always supplied to interrupt motor starting second-ary currents.

AUXILIARY SWITCHThe auxiliary switch mounts on top of the plat-

form to the left of the operating mechanism. (SeeFigs. 15 and 15A). The contacts will carry 15 am-peres continuously or 250 amperes for 3 seconds.

Table No. 4. INTERRUPTING CAPACITY

INTERRUPTING CAPACITY IN AMPERESVOLTS

Non-Inductive Circuit Inductive Circuit

6.2511125 V, D-C250 V, D-C115 V, A-C450 V, A-C

2 1.7575 1525 5

The switch is a shaft-operated, 4-pole, rotary typehaving two 'V' contacts (closed when the breakeris closed) and two "b" contacts (closed when thebreaker is open). The rotor operates through a60-degree angle and is non-adjustable, however,the contacts may be changed from "a" to "b" orvice versa. To change, remove the switch from theFIG. 15. Auxiliary Switch—Location

B A C K C O V E RE N D B U S H I N GSHAFT a

LEVER

CONTACTFI NGERa

jfcvr-xSffrfu,. CONTACT-ROTORIt 3 DO E CASE

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FIG. 15A. Auxiliary Switch—Construction Details

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platform, remove the back cover, shaft and endbushing. Remove the rotor and change the contactsas desired. Be sure to replace the shaft in the orig-inal position relative to one of the unchanged con-tacts.

Maintenance. Check for loose bolts. Replacecontacts if necessary.i

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ALARM SWITCH ATTACHMENT!

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The alarm switch mounts above the shunt tripattachment (see Figs. 16 and 16A) and will energizethe alarm circuit on all opening operations except-ing those initiated through the breaker handle orshunt trip. The alarm switch may be reset manuallyby rotating the breaker handle to the tripped po-sition, or electrically by energizing the shunt tripcoil (when electrical resetting has been provided).

Inspection. Close the breaker manually andtrip by rotating the breaker handle to be sure thealarm contacts do not "make''. Repeat the aboveprocedure except trip by raising the trip bar andnote that the alarm contacts do make contact.

Maintenance. Clean the alarm contacts whennecessary. Check for loose bolts.

Inspection. Remove the front cover and makesure the contacts are touching well before the endof travel.

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ELECTRIC LOCKOUT ATTACHMENT

L- The electric lockout mounts on the underside ofthe platform directly below the undervoltage tripattachment. (See Fig. 17). Its function is to holdthe breaker open (trip free) until the lockout coilis energized. The lockout coil can be de-energizedafter closure of the breaker, if desired. -*' r

Inspection. Rotate the breaker handle to theclosed position. The lockout should prevent closureof the breaker by holding the trip bar in the trip-

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FIG. 16. Alarm Switch Attachment—Locationi

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FIG. 16A. Alarm Switch Attachment—Construction Details<

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*I.B. 35-225-1CMAINTENANCE“DB” AIR CIRCUIT BREAKERS

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FIG. 17. Electric Lockout Attachment—Location and Construction Details\

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FIG. 18. Key Interlock Attachment— Location and Construction Details

tripped position and turn the key to the lockedposition. The key is then removable and the break-er handle is locked in the tripped position. Replacethe key, apply force in the counterclockwise direc-tion to the breaker handle and rotate the key to theunlocked position to free the breaker handle.

Maintenance. The device is non-adjustable.Check for loose bolts only.

TERMINAL BLOCKThe eight point terminal block mounts on top

of the auxiliary switch (see Fig. 19).All internal wiring is connected to the back

terminals, leaving the front terminals for the cus-tomer's wiring. The left side of the front cover isopen to permit entrance of the customer's wiresfrom the left side of the breaker.

Maintenance. Check for loose screws.

Pushing downward on the liftingfree position,

plate should permit closure of the breaker. Re-leasing the lifting plate after closure should not tripthe breaker.

ft Maintenance. The lifting bracket can be movedvertically on the lifting plate by the adjusting screw.This adjustment is made to obtain approximately%2-inch clearance between the lifting bracket andthe bottom of the trip bar, with the lockout coilenergized. Check for open-circuited coil; also checkfor loose bolts and nuts.

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KEY INTERLOCK ATTACHMENTThe key interlock mounts on the right side of

the operating mechanism frame. (See Fig. 18). Thekey cannot be removed unless the breaker is lockedin the tripped position.

Inspection. Rotate the breaker handle to the

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FIG. 19. Terminal Block Attachment—Construction Details

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