A Guide to Contactor

Installation and Maintenance

'Product development is a continuous process. Consequently the data indicated in this leaflet is subject to change without prior notice. For latest issue contact our Sales Office.’

Standard Products DivisionLV Control & Distribution ProductsThane Belapur RoadThane - 400 601Tel:(022) 7600001Fax:(022) 7600076

Siemens Ltd.

SGR-01-101-059(This replaces SGR-01-101-051)

±±

±

±

±±Cyan BlackMagenta Yellow

Cyan BlackMagenta Yellow

CMYK

Installation Guidelines

1.1 InspectionRemove the contactor from itscarton and open the arcchamber if present. Ensure thatthere is no breakage / damageto any of its parts. Check thecoil voltage, frequency andcontact configuration. Ensurecorrectness before installation.Refix arc chamber beforeinstallation.

1.2 MountingMount the contactor on avertical surface either on aDIN rail (if applicable) or withspecified screws (use allmounting holes and the screws,washers, spring washerssupplied). Refer mounting planas shown in fig. 1. Do not drillholes near mounted contactors,to avoid entry of metal dust intothe contactor. Metal dust willaffect its performance. Referfig.2.

Figure 1

2

Figure 2

Contactor MountingType Dimensions in mm

A B3TH 80/82 35 603TB 40/41 35 603TH 30 35 603TF 30/31 35 603TF 42/43 35 753TF 44/45 45 753TF 46/47/477 70 1003TF 48/49 80 1103TF 50/51 100 1303TF 52/53 110 1603TF 54/55 120 1803TF 56/57 130 1803TF 68/69 150 210

3

For 3TF44 to 3TF69, with AC coil or DC coil

For 3TH80/82, 3TB40/41, 3TF42/43 with AC coil

1.3 Control Circuit Wiring

Figure 3

Fig. 3. illustrates thepermissible length of controlcables with commonly usedcross-sections for various ratedcontrol supply voltages and amaximum permissible voltagedrop of 5%.

The permissible length ofcable(m) can also be calculatedby using the formula below :

L : 5 (U)2 dU

R SON cos fffffON

U : Rated coil voltage

dU : Voltage drop ( 5%)

SON : Coil VA / W at pick up

cos fON : p.f of coil at pick up

R : Ohmic resistance/cable values astabulated

C/s of Cu cable R in W /km at &sq mm 70o C

1 21.70

1.5 14.47

2.5 8.71

4.0 5.45

4

SON pick - up power of thecontactor coil for d.c. supply

SON CosfON pick - up power of thecontactor coil for d.c. supplythe contactor coil for a.c. supply

Figure 4

Caution :

When long control cables areused for actuating the contactor,large voltage drop may occurcausing chattering of thecontactor or even failure to pickup. If the length of the cableexceeds L, use of higher size ofcable or use of contactor relay issuggested as shown in fig. 4.

5

K1 - Contactor RelayK2 - Power ContactorSO - Remote Push Button

1.4 Effect of CableCapacitance on theOperation of ACOperatedContactors

When long length of cables isused the stored energy in thecapacitance of the cable holdsthe contactor even after theclosing command is removed;therefore critical cable lengthsmust be adhered to accordingto the table.

1.5 Actuating DeviceIf overload relay is self resettype, use a momentarycommand device to energizethe contactor, to preventautomatic reclosure after anoverload trip.

If overload relay is hand resettype, use momentary ormaintained command device.Hand reset feature of relayprevents automatic reclosureafter an overload trip.

Critical cable length, L

Contactor Momentary Maintainedcommand commandcontrol (m) max control (m) max

3TH 80/82 142 2853TB 40/41 142 2853TH 30 130 2603TF 30/31 130 2603TF 42/43 130 2603TF 44/45 130 2603TF 46/47 416 8333TF 48/49 416 8333TF 50/51 644 13263TF 52/53 754 15103TF 54/55 1098 21853TF 56 1500 29903TF 57 600 10103TF 68/69 1820 3640

6

1.6 Connections for AC Operated Contactors(a) Maintained command control

Figure 6

(b) Momentary command control

7

Figure 5

1.7 Connections for DCOperatedContactors.

DC contactors 3TH 80/82,3TB 40/41, 3TF 42/43 and3TF 44/45 have directlyoperated DC coils with DCmagnet system. 3TF 46-51 withDC coils should be used inconjunction with aux contactblock as depicted in fig. 7.

For 3TF 52-55, a separatecontactor (3TB 40 17 OD)should be connected; Referfig. 8. For 3TF 56, 3TF 42 OB

contactor should be used. Referfig. 9.

Caution :

Please use the correct auxiliarycontact block for connection inthe circuit. Thus, the extendedcontact block used for3TF 46, 47, 477 is 3TY7 461-1Fand for 3TF 48-57 is3TY7 481-1F. This ensuresproper performance.

Employ recommended overloadand short circuit devices whichare properly coordinated.

Figure 7

8

K = Contactor type3TF46 02-OD/3TF47 02-OD/3TF50 02-OD/3TF5102-OD/3TF47 72-ODF1 = FuseF2 = Overload relaySO = Push buttonS1 = Momentary

contact actuatorS = Maintained

contact actuatorI = Hold on windingh = Pick up winding

Momentary Contact Actuation Maintained Contact Actuation

Figure 9

Figure 8

9

K2 = 3TB40 17-ODK1 = Contactor type3TF52 02-ODTO 3TF5502-ODF1 = FuseF2 = Overload relayS = Maintained

contact actuatorI = Hold on windingh = Pick up windingS1 = Momentary

contact actuator

K2 = 3TF42 11-OBK1 = Contactor type3TF56 02-ODF1 = FuseF2 = Overload relayS = Maintained

contact actuatorI = Hold on windingh = Pick up windingS1 = Momentary

contact actuator

Momentary Contact Actuation Maintained Contact Actuation

Momentary Contact Actuation Maintained Contact Actuation

1.8 Varistors / RCElements

When a contactor coil isswitched off, voltage surges aregenerated, these can damagethe associated surge-sensitiveelectronic equipment. In orderto protect such equipment, RCelements & varistors are

provided as accessories; Theseare to be used as snap-fittingaccessories to be fitted on thetop cover (for 3TH 80/82,3TB 40/41, 3TF 42-45) & on theslots in the housing (for3TF 46-56). Refer table below.

Varistor

Coil Voltage For 3TH80/82, 3TB40/41,For 3TF46/56

3TH30, 3TF30/31, 3TF42/45

AC24-48V3TX7402-3GY1 3TX7462-3GY1

DC24-70V

AC48-127V3TX7402-3HY1 3TX7462-3HY1

DC70-150V

AC127-240V3TX7402-3JY1 3TX7462-3JY1

DC150-250V

AC400-600V 3TX7402-3LY1 3TX7462-3LY1

RC Element for3TH80/82, 3TB40/41 &

3TH30, 3TF30/31, 3TF42/43

Coil Voltage

24-48V AC 3TX6 406-OD

110-220V AC 3TX6 406-OC

220-240V AC 3TX6 446-OB

RC Element for 3TF44/45

Coil Voltage

24-48V AC3TX7 402-3RY2

24-70V DC

48-127 AC3TX7 402-3SY2

70-150 DC

127-240 AC3TX7 402-3TY2

150-250 DC

400-600 AC 3TX7 402-3VY2

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1.9 MechanicallyInterlockedContactors

In applications involvingreversing feeders for cranecontrols, mechanically andelectrically interlockedcontactors are recommended.For such applications use3TD 10/11, (9A & 12A),3TD 42/43 (16A, 22A),

mechanically interlockedcontactors which are factorybuilt & prewired are provided.

In the case of 3TF series ofcontactors (3TF 44-69), aninterlocking kit is offered to allowsite-assembly of mechanicallyinterlocked version. Forassembly and wiring diagram ofthe interlocked contactors, referto the instruction sheet providedwith the kit.

CCCCContontontontontactactactactactororororor PicPicPicPicPickup kup kup kup kup VVVVVAAAAA PPPPPooooowwwwwererererer CCCCCapacitapacitapacitapacitapacitororororor MMMMMilliilliilliilliillivvvvvolt drolt drolt drolt drolt dropopopopop CurCurCurCurCurrrrrrent le ent le ent le ent le ent le AAAAAC-3C-3C-3C-3C-3(S(S(S(S(S0N0N0N0N0N))))) fffffactactactactactororororor rrrrratatatatatinginginginging at leat leat leat leat le

(c(c(c(c(cosososososfffff0N0N0N0N0N))))) (KV(KV(KV(KV(KVAR)AR)AR)AR)AR) AAAAAC3 (max)C3 (max)C3 (max)C3 (max)C3 (max)3TB 40 77 0.81 4 87 93TB 41 77 0.81 4 120 123TF 30 68 0.82 4 87 93TF 31 68 0.82 4 120 123TF 42 68 0.82 7.5 82 163TF 43 68 0.82 7.5 123 223TF 44 101 0.83 16.7 7 323TF 45 101 0.83 16.7 9 383TF 46 183 0.6 30 14 453TF 47 183 0.6 30 17 633TF 48 330 0.5 50 14 753TF 49 330 0.5 50 18 853TF 50 550 0.45 60 16 1103TF 51 550 0.45 60 18 1403TF 52 910 0.5 100 15 1703TF 53 910 0.5 100 18 2053 TF 54 1430 0.34 150 9 2503TF 55 1430 0.34 150 13 3003TF 56 2450 0.21 200 17 4003TF 57 1136-1900 1 200 14 4753TF 68 1200-1850 1 300 13 6303TF 69 600-900 0.98 300 14 820

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1.10 Control TransformerRating

To determine the size of acontrol transformer, thefollowing guidelines may beused.

For switching on contactors, thecontrol rating of the transformershould be: 0.33 times the sumof the pick up VAs of thecontactors which are to beswitched on simultaneously.

For e.g. if 3x contactors of3TF43 & 2x contactors of3TF 55 are to be switched onsimultaneously then the totalpickup VA is 3064.

Required control transformerrating: 3064/3 = 1.021 kVA. with5% regulation.

Note: In general, as controltransformers have poorerregulation, usage of higher VAof transformer is recommended.

Figure 10

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1.11 CapacitorSwitching

When capacitors are switchedon, there is a high inrushcurrent for a short duration.

For economical switching ofcapacitors, it is necessary totake additional measures:

1) By switching capacitors on tothe network via dampingresistors: the switching currentsare limited by the resistors.Refer Fig 10. or

2) By connecting 6 u H air coreinductance between parallelcapacitances, having adequatecurrent carrying capacity.

1.12 Star DeltaApplication

For star delta application,7PU 60 20 timers have to be

used to prevent short circuitsduring changeover. This timerprovides definite time delaybetween star and delta andavoids short-circuit, contacterosion / welding.

1.13 CorrosiveAtmosphere

Corrosive atmosphere has aprofound effect on theperformance of contactors.Overheating takes place due tothe formation of foreign films atthe connections and on thesprings. For such applications,contactors have to be suitablyderated. Occasional sprayingwith CRC 2-26 preventsreaction of the silver parts withthe atmosphere and minimizesdamage.

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Maintenance Guidelines

2.1 Routine InspectionInspect terminals, contacts, arcchambers periodically - twomonths after installation andevery six months thereafter.Routine inspections help tomonitor the state of thecontactor. These contribute tothe reliability of the plant andminimize risk of breakdownduring production hours.

2.2 Isolation forMaintenance

Switch off the contactor &upstream devices beforeinspecting the contactor.

Safety Precaution

2.3 TerminalsTighten Terminals periodically

Connections have a tendency toloosen with time - particularlythose of aluminium which is asoft material. The terminalsshould be tightened with atorque specified in the table.

Screws Tighteningtorque N cm

M 3.0 40 - 55

M 3.5 80 - 100

M 4.0 80 - 100

M 5.0 150 - 210

M 6.0 340 - 400

M 8.0 700 - 850

M 10.0 1400 - 1650

2.4 ContactArrangement

Alteration in the contactarrangement i.e from NO to NCor vice versa is forbidden.

Do not remove any unutilisedcontact from the contactor.Such removal will impair thebalance / performance of thecontactor.

2.5 Contact ConditionTarnished / Blackened Contact

Tarnishing is normal for anysilver item, it is due to theformation of silver oxide whichis a good conductor of heat &electricity, hence tarnished

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contacts need not be replaced.Blackened or sooty contactswhich are otherwise in a goodcondition need not be replaced.These contacts can be cleanedwith CRC 2-26.

Do not replace slightly pittedcontact.

Whether a contact is good ornot depends on the volume ofcontact material which remains

in it. Replace contacts whenthe contact tip has become lessthan 40% of its original volume.Refer Fig 11.

Do not employ carbonimpression method to checkhealthiness of contacts.

Do not use abrasives e.g. donot file contacts, do not useemery paper on contacts.

Figure 11

Result of the visual inspection:RRRRReplaceplaceplaceplaceplacement is not necement is not necement is not necement is not necement is not necessaryessaryessaryessaryessary

Result of the visual inspection:RRRRReplaceplaceplaceplaceplacement is not necement is not necement is not necement is not necement is not necessaryessaryessaryessaryessary

Result of the visual inspection:RRRRReplaceplaceplaceplaceplacement is necement is necement is necement is necement is necessaryessaryessaryessaryessary

15

Abrasives remove silver fromthe contact tip & drasticallyreduce the contact life.Do notgrease the contacts.

The contact condition should beinspected after a fault i.e. shortcircuit. If the contacts areslightly welded, separate themwith a screw driver.

Slight but separable weldingdoes not affect the performanceof the contactor performance,its acceptability is recognizedby IS 13947 / IEC 947specifications.

If the contacts are not easilyseparable i.e. permanentlywelded, replace the contactsand use the contactor, providedits other parts are in propercondition.

Replacing the completecontactor is not necessary.

Replace contacts in pairs i.e.fixed & moving contacts ofone pole together. Thisensures proper mating of thecontact tips.

After replacing contacts,operate the contactor a fewtimes before putting it back tonormal service.

Do not replace the contactsafter the mechanical life is

over. Maximum number ofreplacements is about 7; afterwhich the contactor requiresreplacement.

2.6 ARC ChambersDo not operate the contactorwithout the arc chamber asthere is an ARC chamberinterlock.

Do not use broken/crackeddamaged arc chamber.Replace it immediately. Sucharc chambers can causeflashovers.

Replace the arc chamber as perthe instructions depicted on thearc chamber as shown in fig 12.

For closing, press and turn thearc chamber pin through 900

clockwise to ensure properfunctioning of the interlockingmechanism. Operate thecontactor manually. Foropening the arc chamber thepins should be pushed and thenturned through 900 in theanticlockwise direction.

Standard spares are maincontacts (3TF44-69), Arcchambers (3TF44-57), Auxiliarycontact block (3TF 44-69) &Coils.

16

Figure 12

Do not replace parts other thanthe standard spares. Partsother than the standard sparesare designed to last for the lifetime of the contactor.

Do not use ‘repaired’ contacts,arc chambers, coils as sparesas they cannot deliver theperformance of genuine spares.

Contacts of 3TH 80/82, 3TH30,3TF 30/31, 3TB 40/41 need notbe replaced. Siemens doesnot offer these contacts asspares.

2.7 MagnetsIn case of rust/dustaccumulation on the magnetfaces clean them withCRC 2-26 / Chamoi leather. Donot use degreasing agent aspetrol. Dust/rust affectcontactor performance andcause humming.

Do not clean magnets withshare/pointed objects. Filingupsets the mating of themagnet faces. Clean lightly withfine size 00 emery paper ifrequired.

17

2.8 Mechanical LifeWhen the mechanical life of acontactor is over, replace thecomplete contactor. Followingare the indicators of the end ofmechanical life.

• For E shaped magnets, airgap between the centrallimbs is reduced to zero.This is indicated when thereis rubbing of paint on thecentral pole face of the uppermagnet.

• Broken shading ring ofmagnet.

• Flaring of magnet pole faces,hence difficulty in removingcoil.

• Incurable humming

• Sluggish operation

• Contactor does not drop off

18

Figure 13

19

Figure 15

Figure 14

Major Problems in Contactorstheir causes and remedies11111 Excessive pitting and weldingExcessive pitting and weldingExcessive pitting and weldingExcessive pitting and weldingExcessive pitting and welding

of cof cof cof cof contontontontontactactactactacts Chats Chats Chats Chats Chatttttterererereringinginginging• Low voltage - Coil not picking – Ensure correct voltage conditions.

up properly In case of persistent low voltagechange coil to lower voltage or changecontrol transformer tapping

• Broken Short circuit ring – The mechanical life of contactor is over.Replace the contactor

• Chattering in switching device – Check & correct the condition in thecontrol circuit

• Small cross section/long length – Select sizes as per guideline in sect onof control cable control wiring.

• Improper termination of – Use proper lugs for terminationcontrol cable

• Inadequate capacity of control – Use correct control transformer. Refertransformer sect on control transformer rating

• Faulty switching devices/incorrect – Follow wiring diagram and use correctwiring for e.g. In DC contactors auxiliary switch.Sect on connections fornormal NC used in place of DC contactorsextended NC

• Capacitor switching – Use correct contactor & follow guidelines• Short circuit during star delta – Use 7PU 60 20 timer

changeover• Reversing application (cranes) – Use interlocked contactors with

electrical interlocking

22222 OOOOOvvvvvererererer heat heat heat heat heating of main cing of main cing of main cing of main cing of main contontontontontact pathact pathact pathact pathact path• Foreign matter on the magnet – Remove the foreign matter

pole faces or jamming of contactcarrier preventing contact closing

• Improper termination of cables. – Check the millivolt drop across cableImproper cross section of strand/busbar & terminals. The mV dropcable & busbar should be < 4.0 mV at rated currents

otherwise clean busbar or recrimp cableRefer sect. on healthiness of terminals.

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• Presence of harmonics – Suitable derating to be employed.• Improper ventilation of panel – Provide suitable cooling for the panels.33333 NNNNNoisoisoisoisoisyyyyy M M M M Maaaaagnetgnetgnetgnetgnetsssss• Broken shading ring – The mechanical life of contactor

is over• Magnet faces not mating – The mechanical life of contactor

is over• Dirt or rust on magnet faces – Wipe/clean lightly with fine

emery paper size 0044444 FFFFFailurailurailurailurailure te te te te to pico pico pico pico pick up & sealk up & sealk up & sealk up & sealk up & seal• Low voltage – Correct voltage conditions-In case of

persistent low voltage change to lowervoltage coil or change transformer tap

• Coil open or shorted – Replace the coil• Mechanical obstruction – Clean and check free movement

of contact assembly• Coil excitation without arc chute – Ensure proper fitting of arc

or arc chute not properly fixed chute55555 FFFFFailurailurailurailurailure te te te te to dro dro dro dro drop outop outop outop outop out• Coil not disconnected from supply – Check wiring of the coil circuit• Residual magnetism due to – The mechanical life of contactor

lack of air gap in the central is overlimb of the magnet

• Gummy substance on pole – Remove the foreign substancefaces causing binding

66666 OOOOOvvvvverererererheatheatheatheatheating of cing of cing of cing of cing of coiloiloiloiloil• Overvoltage – Check & correct terminal voltage/

replace with higher voltage coil• Undervoltage-failure of magnet – Correct terminal voltage / replace with

to seal in lower voltage coil or changetransformer tap

• Interturn short circuit of Coils – Replace coils(Coil getting Excessively hot -Turned brown in colour)

• Dirt or rust on pole faces – Clean pole faces. Don’t use greaseincreasing the air gap solvents or sharp objects while cleaning

21

Method of Checking Healthiness of Jointsand Contactors• Checking mV drop with an

accurate meter whichindicates< 0.2mV whenshorted

• Twist the connecting leadswhile measuring to avoidfalse pick ups

• Measure current with clip onmeter

• The values of drop measuredshould be less than 4.0mV atthe rated current of contactorfor AC3 duty.

(Note-The mV drop at ratedcurrent can be calculated asmV drop at

=mV drop at

X(Rated current)

rated current actual current (Actual current)

Corrective Action: If values ofmillivolt are more (bad joints)

Case A & B: Clean the surfaces,apply Dowells crimpingcompound & recrimp cables.

Case C : Higher value of mVdrop in this case could be dueto either case A or B; In case ofpersistent higher value,replacement of the entirecontactor is necessary.

a) Cable/Contactor

[ [ [] ] ]

LUG

CONTACTORTERMINAL

BARE WIRE

INSULATION

22

c) Across Contactor

b) Busbar/Contactor

23

A Guide to Contactor

Installation and Maintenance

'Product development is a continuous process. Consequently the data indicated in this leaflet is subject to change without prior notice. For latest issue contact our Sales Office.’

Standard Products DivisionLV Control & Distribution ProductsThane Belapur RoadThane - 400 601Tel:(022) 7600001Fax:(022) 7600076

Siemens Ltd.

SGR-01-101-059(This replaces SGR-01-101-051)

±±

±

±

±±Cyan BlackMagenta Yellow

Cyan BlackMagenta Yellow

CMYK