6. maintenance, inspection and parts replacement … instruction... · krb-5241b 40 6-1. inspection...

KRB-5241b39

6. MAINTENANCE, INSPECTION AND PARTS REPLACEMENT

This chapter describes the maintenance and inspection procedure for the AR series ACBs.

The service life of the ACB depends on the working and environmental conditions. The ACB is exposed to mechanical and

electrical stresses and thus suffers gradual degradation during use, which will increase the possibility of malfunctions. Preventive

maintenance and periodical inspection are very important to isolate any functional degradation, prevent malfunctions, extend the

service life, and ensure safe operation.

The appropriate frequency of maintenance and inspection of the ACB varies depending on the installation conditions, the number

of tripping operations, the magnitude of breaking current, and other factors that are to be considered empirically. As a guideline,

Table 24 shows the recommended inspection frequency. See section 6-1 for detailed maintenance and inspection procedures.

Table 24 Frequency of maintenance and inspection

Frequency in interval or number of open/close cyclesCategory

Working and environmental

conditions

Inspection

level Interval Number of open/close cycles

Open/close

conditionAR208S

AR212S -

AR325S

AR332S

AR440S

Nearly no current

levelEvery 1000 cycles

Normal/

Detailed

• Every year or 2 years

• Every year after 3 years

since installation

• Every half year after 6

years since installationRated current

level

Every 1000

cycles

Every 500

cyclesEvery 100 cycles

Thorough

• Every 5 or 6 years

• Every 4 years after 6 years

since installation

• Every year or 2 years after

10 years since installation

Every 4000 cycles

Normal

• Not so dusty,

• Not so much corrosive

gases,

• Ambient temperature:

35°C or lower

• Not so humid,

• Number of open/close

cycles per day: 2 or less

Ex.Switchboards in electric

installation rooms,

Control rooms,

Building installation Overhaul When abnormality is found during normal or through inspection

Open/close

conditionAR208S

AR212S -

AR325S

AR332S

AR440S

Nearly no current

level

• Every 1000 cycles

• Every 500 cycles after 1000 cyclesNormal/

Detailed

• Every year

• Every half year after 2

years since installation Rated current

level

• Every 1000

cycles

• Every 500

cycles after

1000 cycles

• Every 500

cycles

• Every 250

cycles after

500 cycles

• Every 100

cycles

• Every 50 cycles

after 100 cycles

Thorough

• Every 2 or 3 years

• Every 2 years after 6 years

since installation

• Every year after 10 years

since installation

• Every 2500 - 3000 cycles

• Every 2000 cycles after 3000 cycles

Harsh

• Highly dusty,

• Much corrosive gases,

• Ambient temperature:

45°C or higher,

• Highly humid,

• Number of open/close

cycles per day: 4 or more,

• Always exposed to

vibrations

Ex. Iron or chemical plants

Engine rooms (without

ventilation),

Cogeneration

installation,

FerryboatsOverhaul When abnormality is found during normal or through inspection

Open/close

conditionAR208S

AR212S -

AR325S

AR332S

AR440S

Overcurrent level

(approx. 6 times

the rated current)

Every 25

cycles

Every 25

cyclesEvery 25 cyclesThorough When abnormality occurs

Level exceeding

overcurrent levelEvery time Every time Every time

Abnormal

• Open/close operation due

to overload,

• Tripping due to short-

circuit,

• Accidentally submerged

Overhaul When ACB is deemed to be repairable at through inspection

Normal inspection includes inspection and actions that can be done only with removing the arc chamber, contacts, front cover andthe like. Normal inspection can be performed by the user. Terasaki also provides normal inspection service.

Detailed inspection includes inspection, actions, and parts replacement that will be done to prevent functional degradation causedby aging or the like when abnormality is found during normal inspection.You are recommended to use Terasaki’s detailed inspection service.

Thorough inspection must be left to Terasaki. Overhaul will be done in a Terasaki’s factory.

About the service life

The expected service life of AR series ACBs is approx. 20,000 open/close cycles provided that appropriate inspection,

maintenance, repair, and parts replacement are performed. But, when an ACB performs three times of tripping operation

nearly at the rated breaking current (three standard operating duty cycles), it is at the end of its safe service life even if

thorough inspection is done very time it trips open. Such an ACB will be apt to suffer malfunctions and should be replaced

without delay to avoid frequent inspection and parts replacement.

See section 6-2 for detailed parts replacement procedures.

KRB-5241b 40

6-1. Inspection Procedures

CAUTION ACB maintenance, inspection and parts replacement must be performed by competent persons.

Do not touch ACB current carrying parts and ACB structural parts close to a current carrying part immediately after the

ACB trips open. Remaining heat may cause a burn.

Prior to commencing any work on the ACB, open an upstream circuit breaker or the like to isolate all sources of

power/voltage from the main and control circuits. Otherwise, electric shock may result.

Take care to avoid adhesion of dust to main and control circuit contacts. Dust on the contacts may result in a fire.

Prior to commencing maintenance, inspection, or parts replacement, make sure that the closing springs are released and the

ACB is open. Otherwise, unintentional open/close operation may lead to fingers or tools to be pinched by the open/close

mechanism, resulting in injury.

Retighten the terminal screws periodically to the specified torque. Otherwise, a fire could result.

When grinding a contact tip, be careful to prevent grinding dust from entering the breaker operating mechanism. Wipe the

tip clean after grinding. Otherwise, a malfunction or fire could result.

Do not perform dielectric withstand/insulation resistance tests under other conditions than specified. Doing so may cause a

malfunction.

Be sure to reinstall the arc chamber if removed. Failure to do so or incorrect installation of the arc chamber may result in a

fire or burn.

When charging the closing springs or performing open/close operation of the ACB with the arc chamber, front cover and/or

side covers removed during maintenance or inspection work, do not touch parts other than those required for the above

operation (charging handle, ON/OFF buttons, moving core and the like). Doing so may cause fingers or tools to be pinched,

resulting in injury.

When replacing an auxiliary, do not damage the control wire for the auxiliary or pinch the wire between the auxiliary and

the breaker body. Doing so may cause a malfunction.

To ensure safety, be sure to perform the preparation work described in section 6-2-1 unless otherwise specified in the inspection

procedures. The normal inspection procedure and the detailed inspection procedure are shown in Tables 26 and 27 respectively.

Information you are requested to state

If you want us to take action against an abnormality, contact us while providing us the information shown in Table 25 below.

Our contact is shown at the end of this manual.

Table 25 Information you are requested to state

Item Description Reference

Type AR_____S __ poles with draw-out cradle

Serial No. __________ – ______Rating nameplate

Main circuit rated current Product Specifications

Rated voltage In

Spring charging method Manual charging Motor charging

Rated operation voltage:

CLOSING section on

specification nameplate

Overcurrent release Non Equipped Type: AGR-21__ – _______

Rated control voltage: AC DC _____V

OCR section on


Electrical tripping device Shunt trip device (SHT) Rated voltage: AC DC _____V

Adjustable undervoltage trip device (UVT) Rated voltage: AC DC _____V

TRIPPING section on


Special specification SR: ________ SO: ________OTHERS section on


Working conditions

(Voltage, current,

environment)

-

Symptom of abnormality

(in detail): When, How,

Where, etc.)

-

Inspection done/actions

taken (if any)6-1.

Status quo and schedulePermissible power cut date and time: ____________________

Place where you want us to take action: ____________________

-

The contents of the nameplate should be provided in detail.

Related documents such as product specifications and inspection reports should be provided.

If you have a desired inspection and maintenance schedule, let us know the schedule at your earliest convenience. Our service representative could not meet your last

minute requirement.

KRB-5241b41

Table 26 Normal inspection procedureCheck point No. Check item Description

1Discolorationof conductors

Check connection conductors, main circuit terminals, and current carrying parts for heat discoloration.If such a symptom is found, contact us.

2 Parts missingCheck that screws, bolts, nuts, washers, springs, retainers and the like are not missing. If any partsare missing, contact us.

3Damage toparts

Check for deformation, cracks, chips, or other damage of parts. If damage is found, contact us.General

4Dustaccumulation

Check that no dust is accumulated in ACB. If dust is accumulated, use vacuum cleaner to removedust and wipe off with dry, clean cloth.

Main/controlcircuit terminalsSee 2-3.

5 Connections

Check main circuit terminal screws, ground terminal screw, auxiliary switch terminal screws, controlcircuit terminal screws, and position switch terminal screws for looseness. If loose, tighten to specifiedtorque. If #187 tab terminals are used, check that receptacle terminals are inserted correctly. Ifincorrect, reinsert correctly.

Main/controlcircuit contacts

6Surfacecondition

Check that contacts have no dust accumulation and discoloration. If dust is accumulated, use vacuumcleaner to remove dust and wipe off with dry, clean cloth. If surface is discolored badly, polish it with#200 sandpaper. * For main circuit contacts, apply contact grease (SS grease, No. F-5G, FUJIKAGAKU SANGYO) to contact surface after cleaning. Excessive grease may foster dust accumulation. Grease should be applied lightly. Blackening of contacts is caused by oxidation or sulfuration and has no harmful effect except in

extreme cases. If heat discoloration, arc marks, roughness, or peeling of plating layer is found,contact us.

Arc chamberSee 6-2-2.

7Dustaccumulation/Damage

Remove arc chamber and check it for foreign object or dust accumulation, deformation, cracks, chipsand other damage. If foreign matter or dust is accumulated, use vacuum cleaner to remove foreignmatter of dust and wipe off with dry, clean cloth. If metal spatters are adhered, use sandpaper toremove them. * If arc chamber has stubborn adherents suffers damage, replace arc chamber.

8Surfacecondition

Remove arc chamber and check contact circumference, contacts, and contact tips for foreign objector dust accumulation, deformation, cracks, chips and other damage. If dust is accumulated, usevacuum cleaner to remove dust and wipe off with dry, clean cloth. If contact tips are badly discoloredor roughened, polish with #200 sandpaper. * If contact tip suffers damage or is less than 0.7 mm thickafter polishing, replace both moving and stationary contacts. Blackening of contact tips is caused by oxidation or sulfuration and will be removed during closing

operation. It has no harmful effect except in extreme causes. If heat discoloration is found,perform detailed inspection.

ContactsSee 6-2-2, 6-2-3and 6-2-4.

9Looseness ofscrews

Check moving and stationary contact mounting screws A and B for looseness. If loose, retighten.

Main circuit, ArcchamberSee 6-2-2.

10Insulationresistance

Use DC500V Megger to check that insulation resistance between main circuit terminals, betweenmain circuit terminal group and ground, and between ends of adjacent grids exceeds 5M ohm. Ifresistance does not exceed 5M ohm, use sandpaper to remove carbonized portions of insulationaround contacts or current carrying parts and/or spatters adhered to arc chambers and arcextinguishing grids. If problem persists, contact us.

OperatingmechanismSee 6-2-7.

11Internalmechanism

With OCR removed, check internal mechanism for missing parts, deformation, cracks, chips, foreignmater or dust accumulation, breakage of springs, and rust. If foreign matter or dust is accumulated,use vacuum cleaner to remove foreign matter of dust and wipe off with dry, clean cloth. If any partsare missing or damaged or springs are broken, contact us.

Control circuitSee 6-2-5.

12 WiringRemove side and front covers, check that wiring is properly connected, and not disconnected nordamaged. If incorrect connection is found, connect correctly. If disconnection or damage is found,contact us.

State ofoperation lever

Current conductingbetween _11 and _12

Current conductingbetween _11 and _14

Natural position 100 m or less Non13 Operation

Check that auxiliary switchesoperate as shown to the right.If not so, replace switches.

Uppermost liftposition

Non 100 m or less

14Auxiliarycontacts

Remove auxiliary switches and check contacts for roughness. If roughened excessively, replacecontacts.

AuxiliaryswitchesSee 6-2-9.

15Looseness ofscrews

Check screws of auxiliary switches for looseness. If loose, retighten.

16Draw-out/insertionmechanism

Draw out and insert breaker body to check that draw-out handle can be turned with max. operatingtorque or less, position indictor provides correct indication, release button operates normally, and noabnormal sound is heard during handle operation. If abnormality is found, contact us.

17 UVTWith breaker body in ISOLATED position, charge closing springs manually and attempt closing ACBto make sure ACB cannot be closed. If ACB can be closed, perform detailed inspection.

OperationrelatedmechanismSee 4-1 and 4-2.

18

Operationmechanism,LRC, SHTand UVT

With breaker body in TEST position and control/operation circuits, SHT and UVT supplied with power,perform closing spring charging operation and manual and electrical open/close operation severaltimes to check that charging indicator, ON-OFF indicator and ON-OFF cycle counter providecorrection indication and no abnormal sound is heard. If abnormality is found, perform detailedinspection.

OCR and TC 19 System alarmMove the breaker body to TEST position and supply ACB with control power, and then check thatsystem alarm LED on OCR front panel is off. If LED is on, press reset button and make sure LEDturns off. If LED remains on, see chapter 7.

* Take care to avoid grinding dust from entering the ACB. Wipe contact surfaces clean of grinding dust.

KRB-5241b 42

Table 27 Detailed inspection procedureCheckpoint

No. Check item Description

1

Partingdistance

With ACB open, remove arc chamber and, using feeler gauge, make sure distance between moving

and stationary contact tips is 20 1mm. If not so, replace both moving and stationary contacts. If it is

useless to replace contacts, contact us.

2 Engagement

Insert 3.5 - 4.0-mm-dia x 50-mm-length rod into engagement measuring hole vertically until it stops,

and measure protrusion of rod when ACB is open and closed. Make sure difference in protrusion is 2

0.5 mm. If not so, replace both moving and stationary contacts. If it is useless to replace contacts,

contact us.

3 DisplacementWith ACB closed, remove arc chamber and, using graduated ruler, make sure displacement betweencorresponding contact tips is within 2 mm. If displacement is 2 mm or more, replace both moving andstationary contacts. If it is useless to replace contacts, contact us.

ContactsSee 6-2-2,6-2-3 and6-2-4

4 Resistance

With ACB closed, remove arc chamber and, using tester, make sure resistance between moving and

stationary contact tips is not more than 100 µΩ. If not so, replace both moving and stationarycontacts. If it is useless to replace contacts, contact us. After inspection, open ACB and dischargeclosing springs.

CurrentsensorsSee 6-2-3.

5Looseness ofscrews

Check current sensor mounting screws for looseness. If loose, retighten.

6Coilresistance

Disconnect hand connector (green) and, using tester, measure coil resistance between terminals andmake sure it is within range specified in Table 9. If not so, replace LRC.

7Length andstroke ofplunger

Remove LRC and, using vernier caliper, make sure plunger length is 24.2 - 24.8 mm in natural stateand protrusion of plunger is 6.3 - 7 mm when moving core is pushed in. If not so, replace LRC.

8Handconnector

Check that hand connector (green) is connected to ACB hand connector (green) correctly. If incorrect,connect correctly.

9Looseness ofscrews

Check LRC mounting screws for looseness. If loose, retighten.

Latchrelease coil(LRC)See 6-2-5.

10Mechanicalmotion

With closing springs charged, check that pushing moving core results in ACB being closed slowly,and releasing moving core results in the core being restored smoothly. If not so, replace LRC. If it isuseless to replace LRC, contact us. After inspection, open ACB and discharge closing springs.

11Coilresistance

Disconnect hand connector (black) and, using tester, measure coil resistance between terminals andmake sure it is within range specified in Table 10. If not so, replace SHT.

12Length andstroke ofplunger

Remove SHT and, using vernier caliper, make sure plunger length is 24.2 - 24.8 mm in natural stateand protrusion of plunger is 6.3 - 7 mm when moving core is pushed in. If not so, replace SHT.

13Handconnector

Check that hand connector (black) is connected to ACB hand connector (black) correctly. If incorrect,connect correctly.


Check SHT mounting screws for looseness. If loose, retighten.

Shunt tripdevice(SHT)See 6-2-6.

15Mechanicalmotion

With ACB closed, check that pushing moving core results in ACB being opened slowly, and releasingmoving core results in the core being restored smoothly. If not so, replace SHT. If it is useless toreplace SHT, contact us. After inspection, discharge closing springs.

16Coilresistance

Disconnect hand connector (red) and, using tester, measure coil resistance between terminals and

make sure it is 1.8 - 2.2 Ω. If not so, replace UVT.

17 OperationRemove UVT and pull out moving core slowly, and make sure pushing moving core allows core to besmoothly retracted and attracted. If not so, replace UVT.

18Length andstroke ofmoving core

Remove UVT and, using vernier caliper, make sure moving core length is 2.2 - 2.8 mm in pushedstate and protrusion of moving core is 6.7 - 7.3mm in pulled-out state. If not so, replace UVT.

19Handconnector

Check that hand connector (red) is connected to ACB hand connector (red) correctly. If incorrect ,connect correctly.

Adjustableundervoltage tripdevice(UVT)See 6-2-7.


Check UVT mounting screws for looseness. If loose, retighten.

21Coilresistance

Disconnect hand connector (red) and, using tester, measure coil resistance between terminals and

make sure it is 1.8 - 2.2 Ω. If not so, replace TC.

22 OperationRemove TC and pull out moving core slowly, and make sure pushing moving core allows core to besmoothly retracted and attracted If not so, replace TC.

23Length andstroke ofmoving core

Remove TC and, using vernier caliper, make sure moving core length is 2.2 - 2.8 mm in pushed stateand protrusion of moving core is 6.7 - 7.3mm in pulled-out state. If not so, replace TC.

24Handconnector

Check that hand connector (red) is connected to ACB hand connector (red) correctly. If incorrect ,connect correctly.

Trippingcoil (TC)See 6-2-7.


Check TC mounting screws for looseness. If loose, retighten.

Chargingmotor andLRC

26Electricaloperation

With breaker body assembled to original state, move breaker body to TEST position, supply ACB withcontrol and operation power, and attempt to perform motor charging and electrical closing operationwith max. and min. voltages within permissible charging/closing voltage range to make sure ACBoperates normally. (See Table 9). If ACB does not operate normally, contact us.

SHT 27Electricaloperation

With breaker body assembled to original state, move breaker body to TEST position, close ACB,supply SHT with power, and attempt to perform electrical opening operation with max. and min.voltages within permissible closing voltage range to make sure ACB trips open normally. (See Table10). If ACB does not trip open, contact us.

UVT 28Electricaloperation

With breaker body assembled to original state, move breaker body to TEST position, charge closingsprings, and make sure that ACB closes when UVT power supply is supplied with attraction power.And decrease UVT supply voltage to make sure ACB opening voltage is within specified openingvoltage range. (See Tables 19 and 20.) If ACB does not operate normally, contact us.

OCR andTC

29 OperationWith breaker body assembled to original state, perform “OCR + ACB” test described in 5-5. “OCRFunction Check” to make sure ACB operates normally. If ACB does not operate normally, contact us.

KRB-5241b43

6-2. Parts Replacement Procedure

CAUTION ACB maintenance, inspection and parts replacement must be performed by competent persons.

Do not touch ACB current carrying parts and ACB structural parts close to a current carrying part immediately after the

ACB trips open. Remaining heat may cause a burn.

Prior to commencing any work on the ACB, open an upstream circuit breaker or the like to isolate all sources of

power/voltage from the main and control circuits. Otherwise, electric shock may result.

Take care to avoid adhesion of dust to main and control circuit contacts. Dust on the contacts may result in a fire.

Prior to commencing maintenance, inspection, or parts replacement, make sure that the closing springs are released and the

ACB is open. Otherwise, unintentional open/close operation may lead to fingers or tools to be pinched by the open/close

mechanism, resulting in injury.

Be sure to reinstall the arc chamber if removed. Failure to do so or incorrect installation of the arc chamber may result in a

fire or burn.

When replacing an auxiliary, do not damage the control wire for the auxiliary or pinch the wire between the auxiliary and

the breaker body. Doing so may cause a malfunction.

6-2-1. Preparation

Be sure to make the following preparations for parts replacement in order to ensure safety.

1) Open an upstream circuit breaker or the like to isolate all sources of power/voltage from the main and control circuits.

2) Draw out the breaker body to the removed position, and remove it using an optional lifter or lifting plate. Refer to sections 4-

2-2 and 2-1-2.

3) Discharge the closing springs and open the ACB. The procedure varies depending on whether or not the ACB is equipped

with the adjustable undervoltage trip device (UVT).

When the ACB is not equipped with the adjustable undervoltage trip device (UVT):

Perform manual closing/opening operation of the ACB. Refer to sections 4-1-2 and 4-1-3.

When the ACB is equipped with the adjustable undervoltage trip device (UVT):

(1) Turn the cover mounting screws five or six turns to loosen as shown in Fig. 41. If the ACB is equipped with side covers,

first remove the side covers and then loosen the front cover mounting screws. (The cover mounting screws are of captive

type and cannot be removed from the side and front covers.)

Location of cover mounting screws

Fig. 41 Cover mounting screws

Cover mounting screw (captive),Pan head M5 x 20 (4 - 8)with spring and flat washersTightening torque: 2.7 - 3.5 N·m

Front cover

AR2 series ACBwith 3 poles

AR2 series ACBwith 4 poles

AR3/4 series

Front cover

Side covers

Cover mountingscrews

KRB-5241b 44

(2) Pull out the front cover 3 or 4 cm as shown in Fig. 42.

Fig.42 Pulling out the front cover

(3) Use a flatblade screwdriver to raise the moving core of the UVT until the core no longer returns. To do this, insert the

blade of the screwdriver between the core and metal plate top end and pry the core up. See Figs. 43 and 44.

Fig. 43 Location of the moving core

Fig. 44 Raising the moving core

(4) Perform manual closing/opening operation of the ACB. See sections 4-1-2 and 4-1-3.

(5) After inspection, reinstall each part and component as described below.

(6) Use a flatblade screwdriver to press down the UVT lock pin as shown in Figs. 45 and 46.

Front cover

3-4 cm

UVT

Moving core Flatblade screwdriver

UVT

Moving coreMetal Plate

KRB-5241b45

Fig. 45 Location of the lock pin

Fig. 46 Pressing down the lock pin

(7) Push the front cover in place and secure with the front cover mounting screws. If the ACB has side covers, install

them with the side cover mounting screws.

When installing the front cover, first install and torque a cover mounting screw at the upper left corner of the

cover while aligning the screw with the corresponding mounting hole. If unaligned, make sure the lock pin has

been pressed down.

UVT

Lock pin

KRB-5241b 46

6-2-2. Arc chambers

The following describes how to replace arc chambers.

1) Make preparations for parts replacement. Refer to section 6-2-1.

2) Carefully lay the breaker body on spacers with the backside down as shown in Fig. 47. The spacers must be at least 7-cm

high to prevent deformation of protrusions on the breaker body backside, and have the size and strength that allow the

breaker body to be safely laid on them. Take care to keep the main circuit contacts clean of dust.

Fig. 47 Laying the breaker body on spacers

3) Turn the arc chamber mounting screw eight or ten turns to loosen as shown in Fig. 48. (The arc chamber mounting

screws are of captive type and cannot be removed from the arc chamber.)

Arc chambers (at the top) Arc chambers (at the bottom)

Fig. 48 Arc chamber mounting screws

4) Holding the arc chamber mounting screw, remove the arc chamber.

5) Reinstall each part or component in reverse order of removal after inspection.

Fig. 49 shows a removed arc chamber.

Fig. 49 Arc chamber

Arc chambers (6 - 8)

Arc chamber mounting screw(captive),Pan head M6 (12 - 16)with spring and flat washersTightening torque: 4.7 - 5.9 N·m

Spacer

7 cm or higher

Breaker body

Arc extinguishing grids

Arc chamber mountingscrew

KRB-5241b47

6-2-3. Stationary contact

The following describes how to replace the stationary contact. Fig. 50 shows the general view around the stationary contact.

Fig. 50 General view around the stationary contact


2) Unscrew the current sensor mounting screws and remove the current sensor and the power supply CT located behind the

sensor. Do not disconnect the control wire hand connectors from the current sensor and power supply CT. Place the

removed current sensor and CT on the breaker body or floor while avoiding the control wire from being strained.

Fig. 51 Stationary contact

3) Unscrew stationary contact mounting screws A and B.

Main circuit contact

Stationary contact

Stationary contact tip

Moving contact tip

Moving contact

Insulated operating rod

Mold base

Engagement measuring hole

Moving contact mounting screw,Hex. socket head M8 x 30-2 (3)with spring and flat washersTightening torque: 14.7 N·m

Stationary contact mountingscrew A,Pan head M6 x 16-2 (6)with spring and flat washersTightening torque: 4.7 - 5.9 N·m

Stationary contact mountingscrew B,Pan head M6 x 20-2 (6)with spring and flat washersTightening torque: 4.7 - 5.9 N·m

Current sensor mountingscrews,Pan head M4 x 12 (6)with spring and flat washersTightening torque: 1.3 - 1.7 N·m

Stationary contact mountingscrews A,Pan head M6 x 16 (12)with spring and flat washersTightening torque: 4.7 - 5.9 N·m

Stationary contact mountingscrews B,Pan head M6 x 20 (12)with spring and flat washersTightening torque: 4.7 - 5.9 N·m

Allen wrench holes(marked with while lines)

Engagement measuring hole(marked with while line)

Current sensor

KRB-5241b 48

4) Tilt and remove the stationary contact as shown in Fig. 52.

Fig. 52 Removing the stationary contact

5) Reinstall each part or component in reverse order of removal after inspection. As to the moving contact-related parts,

however, install the insulated operation rod, insulation plate, spacer, moving contact, upper separator, lower separator,

flat washer, spring washer, and moving contact mounting screw in this order. See Fig. 53.

6) After installing the moving and/or stationary contact, be sure to perform 10 - 20 cycles of open/close operation and then

retighten the contact mounting screws to the specified torque.

Fig. 53 shows the contacts in closed and open state.

Open state Closed state

Fig. 53 State of contacts

Openingdistancemeasuringpoints

Closed statecheck points

Resistancemeasuringpoints

Current sensor

Control wire

Stationary contact(removed)

Power supply CT

Stationary contact(tilted)

KRB-5241b49

6-2-4. Moving contact

The following describes how to replace the moving contact.


2) Remove the arc chambers and stationary contact. Refer to sections 6-2-2 and 6-2-3.

3) Insert an Allen wrench of a nominal diameter of 5 into each of the Allen wrench holes shown in Fig. 51, turn each

moving contact mounting screw two or three turns to loosen, and raise and remove the upper separator shown in Fig. 54.

4) Supporting the spacers (the number of which varies depending on the poles), the moving contact, the lower separator, and

the moving contact mounting screws by hand, turn the moving contact mounting screws additional two or three turns to

remove these parts. Fig. 55 shows the moving contact-related parts.

Fig. 55 Moving contact-related parts

5) Reinstall each part or component in reverse order of removal after inspection. As to the moving contact-related parts,

however, install the insulated operation rod, insulation plate, spacer, moving contact, upper separator, lower separator,

flat washer, spring washer, and moving contact mounting screw in this order. See Fig. 54.

6) After installing the moving and/or stationary contact, be sure to perform 10 - 20 cycles of open/close operation and then

retighten the contact mounting screws to the specified torque.

Lower separator

Upper separatorMoving contact tip

Moving contact

Insulated operating rod

Spacer

Moving contact mountingscrew,Hex. socket head M8 x 30-6 (8)with spring and flat washersTightening torque: 14.7 N·m

Fig. 54 Moving contacts

Lower separator

Upper separatorMoving contact

Spacer

Moving contactmounting screw

KRB-5241b 50

6-2-5 Latch release coil (LRC)

The following describes how to replace the latch release coil (LRC).


2) If the ACB is not equipped with the adjustable undervoltage trip device, turn the cover mounting screws five or six turns

to loosen as shown in Fig. 41. If the ACB is equipped with side covers, first remove the side covers and then loosen the

front cover mounting screws. (The cover mounting screws are of captive type and cannot be removed from the side and

front covers.)

3) Pulling the charging handle down, remove the front cover.

4) Remove the contact block fixing screws as shown in Fig. 56.

Fig. 56 Removing the contact block fixing screws

5) Flip up the contact block as shown in Fig. 57.

Fig. 57 Flipping up the contact block

6) Turn the LRC mounting screws eight or ten turns to loosen, disconnect the manual connector (green), and then remove

the LRC. See Fig. 58. (The LRC mounting screws are of captive type and cannot be removed from the LRC.)

Fig. 58 Removing the LRC

Contact block Contact block fixing screw,Pan head M5 x 10 (2)with spring and flat washersTightening torque: 2.7 - 3.5 N·m

Front cover

Contact block

LRC

Contact block LRC mounting screw (captive),Pan head M4 x 80 (2)with spring washerTightening torque: 1.3 - 1.7 N·m

Hand connector(green)

KRB-5241b51

7) Reinstall each part or component in reverse order of removal after inspection. When installing the LRC, make sure the

nameplate on the LRC can be viewed from the front of the ACB.

Fig. 59 provides the general view of the LRC.

Fig. 59 General views of LRC

PlungerHand connector (green)

Moving core

located in the center hole

LRC mounting screw

KRB-5241b 52

6-2-6. Shunt trip device (SHT)

The following describes how to replace the shunt trip device(SHT).





front covers.)


4) Remove the contact block fixing screws as shown in Fig. 56.

5) Flip the contact block up as shown in Fig. 57.

6) Turn the SHT mounting screws eight or ten turns to loosen, disconnect the manual connector (black), and then remove

the SHT. See Fig. 60. (The SHT mounting screws are of captive type and cannot be removed from the SHT.)

Fig. 60 Removing the SHT

7) Reinstall each part or component in reverse order of removal after inspection. When installing the SHT, make sure the

nameplate on the SHT can be viewed from the front of the ACB.

Fig. 61 provides the general view of the SHT.

Fig. 61 General view of SHT

Hand connector(black)

Contact block

SHT mounting screw (captive),Pan head M4 x 80 (2)with spring washerTightening torque: 1.3 - 1.7 N·m

SHT

LRC

Plunger

Hand connector (black)

Moving core

located in the center hole

SHT mounting screw

KRB-5241b53

6-2-7. Tripping coil (TC) or adjustable undervoltage trip device (UVT)

The tripping coil (TC) and the adjustable undervoltage trip device (UVT) are the same in installation position and replacement

procedure. The TC allows overcurrent release only and the UVT allows both overcurrent release and undervoltage trip operation.

The TC/UVT replacement procedure is as follows:





front covers.)


4) If the ACB is equipped with the ON-OFF cycle counter, disengage the hook located under the cycle counter spring, turn

the cycle counter fixing screw two or three turns to loosen (do not remove), and flip the cycle counter up to the upper

right direction. See Fig. 62.

Fig. 62 Flipping up the ON-OFF cycle counter

5) Remove the hand connector (black) from the OCR, remove OCR mounting screws 1 and 2, and remove the OCR. See Fig.

63. Place the OCR on the floor without removing the wiring at the OCR bottom.

Fig. 63 OCR and related parts

ON-OFF cycle counter fixingscrew,Pan head M5 x 10with spring and flat washersTightening torque: 2.7 - 3.5 N·m

ON-OFF cycle counter(flipped up)

Hook for ON-OFFcycle counter spring

OCR mounting screw (1),Pan head M4 x 65 (2)with spring and flat washersTightening torque: 2.7 - 3.5 N·m

OCR mounting screw (1)

Hand connector (black)

OCR mounting screw (2),Countersunk M4 x 8with toothed washersTightening torque:1.3 - 1.7 N·m

Wiring at the OCRbottom

KRB-5241b 54

6) Unscrew the TC mounting screws shown in Fig. 64, disconnect the hand connector (red, 1 for TC or 2 for UVT), and

remove the TC or UVT.

Fig. 64 Removing the TC or UVT

7) Reinstall each part or component in reverse order of removal after inspection. The UVT has two hand connectors (red);

there are two connection combinations whichever is proper.

Figs. 65 and 66 provide the general view of the TC and the UVT respectively.

Fig. 65 General view of TC

Fig. 66 General view of UVT

TC mounting screwPan head M4 x 8 (2)with spring and flat washersTightening torque: 1.3 - 1.7 N·m

Hand connector (red)

UVT

TC mounting screw

Hand connector (red)

Moving core

To remove the movingcore, insert a small rodinto the center hole onthe skew and, holdingthe rod, lift the core.

Hand connector (red)Moving core

To remove themoving core, pressdown the lock pin.

Lock pin

KRB-5241b55

6-2-8. Auxiliary switches

The following describes how to replace auxiliary switches.

1) Make preparations for parts replacement. Refer to section 6-2-1, 1) and 2).

2) If the ACB is equipped with the control terminal block cover, loosen both the cover fixing screws and remove the cover.

3) Remove the auxiliary switch mounting screws shown in Fig. 67.

Fig. 67 Auxiliary switches and related parts

4) Depressing the AUX lock lever shown in Fig. 68, raise the operation lever.

Fig. 68 AUX lock lever and operation lever

Auxiliary switches

Auxiliary switch mounting screw,Pan head M4 x 10 (4 - 6)with spring and flat washersTightening torque: 1.3 - 1.7 N·m

Cover fixing screw

AUX lock lever

Operation lever

KRB-5241b 56

5) With the operation lever raised, uplift the auxiliary switch unit, pull the shaft lever through the U-notch, and remove the

auxiliary switch unit.

Fig. 69 Removing the auxiliary switches

6) Reinstall each part or component in reverse order of removal after inspection. When installing the auxiliary switch unit,

apply molybdenum grease to the engagement of the operation lever and the shaft lever.

Auxiliary contacts can be checked visually through the inspection holes shown in Fig. 70.

Fig. 70 Checking auxiliary contacts

Operation lever

Shaft lever

Inspection holesAuxiliary contact

Shaft lever

KRB-5241b57

7. TROUBLESHOOTING FLOWCHARTS

Figs. 71 - 75 are troubleshooting flowcharts where typical troubles and remedial actions are shown.

Fig. 71 Remedial actions against a symptom of "system alarm LED on"

Fig. 72 Remedial actions against a symptom of "charging impossible"

Yes

NoIs manual charging

possible?

Closing springs cannot becharged

NGCheck the charging

mechanism. See No. 11 inTable 27.

Repair/replace

Contact Terasaki.

No

Is manual charging

possible?

OK

Contact Terasaki.

Yes

OK

NG

Check the control/operationvoltage.

Repair/replace

OK

NGCheck the controlcircuit and terminals. See

Nos. 5 and 12 in

Table 27.

Repair/replace

No

YesIs motor charging

possible?

Contact Terasaki.

End

OK

NG

Repair/replaceCheck the operating


No

Are operation indicationLEDs excluding PTA

on?

Yes

Do the LEDs turns offwhen the reset button is

pressed?

End

Repair/replace

Check

the control circuit

and tripping coil (TC). See No.

12 in Table 27 and Nos.

21-25 in Table

28.

Check the tripping


End

Contact Terasaki.

The system alarmLED is on.

No

Yes

NG

OK

OK

NG

KRB-5241b 58

Fig. 73 Remedial actions against a symptom of "closing impossible"

No

YesIs manual closing

possible?The ACB cannot be closed.

No

YesDoes the operation

mechanism work well?

Yes

NoAre closing springs

charged?Charge

OK

NG

Check the control/operationvoltage.

Repair/replace

OK


Nos. 5 and 12 in

Table 27.

Repair/replace

OK

NGCheck LRC. See Nos. 6 -

10 in Table 28.Repair/replace

No

YesIs electrical closing

possible?

Contact Terasaki.

End

No

YesAre operation indication

LEDs excluding PTA on?Check downstream circuits.

OK

NGCheck contacts. See

Nos. 8 and 9 in Table 27and Nos. 1 - 4 in

Table 28.

Repair/replace

OK

NGCheck the operation


Repair/replace

Yes

NoIs manual closing

Possible?Contact Terasaki.

OK

NGCheck SHT, TC and UVT.See Nos. 15, 17 and 22 in

Table 28.

Repair/replace

OK

NGCheck the operationmechanism. See No. 11 in

Table 27.

Repair/replace

Yes

NoIs manual closing

possible?

No

YesIs the ACB body in anintermediate position?

Move the body to the “CONN.”,“TEST” or “ISOLATED” position.

No

Yes

Is the OFF button locked

or any other OFF-lockactive?

Unlock

No

YesIs the SHT trip command

active?Deactivate

OK

NGCheck the UVT attraction

voltage.Repair/replace

Contact Terasaki.

KRB-5241b59

Fig. 74 Remedial actions against a symptom of "opening impossible"

Fig. 75 Remedial actions against an overheat

Yes

NoIs manual opening

possible?Contact Terasaki.

The ACB cannot be opened.

OK

NGCheck thecontrol/operation voltage

and SHT Voltage.Repair/replace

OK


Nos. 5 and 12 inTable 27.

Repair/replace

No

YesIs electrical opening

possible?

Contact Terasaki.

End

OK

NGCheck SHT, TC and UVT.See Nos. 11 - 25 in Table

28.

Repair/replace

Yes

NoIs the ambient temperature

as specified?Correct/adjust

An overheat occurs.

Yes

NoIs the load current as

specified?

Yes

NoAre OCR settings

correct?Correct/adjust

OK

NG

Check the control circuit. Repair/replace

OK

Check the trippingmechanism. See No. 29 in

Table 28.

No

YesAre main circuit

terminal screws loose?See No. 5 in Table 27.

Retighten

OK

NGCheck main circuitcontacts. See No. 6 in

Table 27.Repair/replace

OK

NGCheck contacts. See

Nos. 8 and 9 in Table 27and Nos. 2 - 4 in

Table 28.

Repair/replace

No

Yes

Is the problem solved?

Contact Terasaki.

End

NGContact Terasaki.

6. maintenance, inspection and parts replacement … instruction... · krb-5241b 40 6-1. inspection...

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