type m tap changer

2

On Load Tap Changer Type MOperating Manual

1. General1.1 Operational principal of the on-load

changer (fig.1)

A tap-change operation begins with the tap selectorpreselecting the desired tap on the transformerwinding.

The diverter switch transfers the current from thetap in service to the preselected tap. During this quickchange-over, ohmic resistors are inserted in the cir-cuit to ensure no-break transfer of the current.

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1.2 Designation of an-load tapchanger models (fig.2)

Every type of tap changer isavailable in a number of differentmodels. These design varyaccording to: number at poles,max rated through current,insulation to ground, tap sectorsize, and basic circuit diagram.

The designation incorporates allthese characteristics and permitseasy identification of the tapchanger. The basic circuitdiagram code in the modeldesignation identifies: number ofoperating positions, number ofmid-positions, and type of change-over selector.

Example in Fig.2:

On-load tap changer type M

single-pole, max rated through-current 500A, insulation to groundaccording to Um = 123 kV, tapselector size B, basic circuitdiagram code 10 19 1 Wmeaning: 10 contacts, 19operating positions, with one mid-position, change-over selectorused as reversing switch

1.3 Principal parts of the on-load tap changer (fig. 3)

The principal parts of the unloadtap changer are

- the tap changer nead

- the diverter switch oilcompartment and

- the tap selector

Diverter switch unit & Top driveunit on tap head are subject toinspection

ON-LOAD TAP CHANGER

M I 501 - 123 / B - 10 19 1W

Type Basic Circuit diagram

Number ofPoles Tap selector size

Max. rated through.current in amperesand additonal indicationof model

Highes voltage forequipment Um

Insulation go ground

BASIC CIRCUIT DIAGRAM

10 19 1 W

Pitch of Max. number of Mid-positions Change-overtap selector service positions 1 selector

contact circle 013

Change-over coarse Reversingselector tap selector switch

without with G W10 10 09 19 *) No designation without12 12 11 23 change-over selector14 14 13 2716 16 15 3118 18 17 35

Fig.2 Designation of Tap Changer model and basic circuit diagram

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Fig. 3 Centric Upper Gear Unit

Principal parts of the on-load tap changer

13 Tap changer head gasket

14 Position Indicator

15 lnspection glass

16 Drive shaft for position Indicator

21 Tap changer head

22 Cover bolt

23 Head cover gasket

24 Tap changer head cover25 Upper gear unit with drive shaft 25a26 Pipe connection R for protective relay27 Pipe connection S for suction pipe28 Pipe connection Q for return pipe

(with oil filter unit only)

29a Bleeder valve of tap changer head cover29b Bleeder facility for transformer oil29c Bleeder screw for suction pipe

31 Diverter switch oil compartment

32 Bottom of oil compartment

33 Grading rings

34 Terminal of diverter switch oil compartment

35 Suction pipe

41 Tap selector support42 Tap selector gear43 Fine tap selector44 Change-over selector45 Tap selector terminal

51 Diverter switch unit

52 Support cylinder

53 Support plate

54 Fixing screw

55 Lifting lug

56 Transition resistors

Principal parts of the on-load tap changer

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1.4 Inspection intervalsIMPORTANT : We recommendinspection of the tap changerequipment at regular intervalsto maintain a high level ofoperating reliability.In general, the inspection can becarried out within one day by E-MR qualified and trainedpersonnel provided it is wellprepared and organized.

We strongly recommend to havein-spections performed by ourTechnical Service. ThisGuarantees a professionalperformance including all thelatest updating of specificcomponents to the latestoperation state.

Inquire for spare parts whenpreparing an Inspection whichshall not be carried out by E-MRpersonnel (please indicate tapchanger number and number ofoperations).

The number of tap changeoperations determining theInspection intervals indicated inTable 1 are figures based onexperience with use of usual oilqualities.

Regardless of the number ofoperations we recommendinspection after 6 to 7 years ofservice, or after 4 years ofservice, if the tap changeroperating voltage is > 220 kV.

The tap selectors of our on-loadtap changers are generallymain-tenance-free. However,special care should be taken withspecial applications. This appliese.g. to industrial transformerswhere high numbers of tapchange operations are to beexpected. Here we recorr-mendto contact our Technical Serviceafterabout 1,000,000 operations.

The divertor switch unit of the tapchanger has to be replaced by anew one after about 800,000

operalion latest.

If the number of operations peryear Is 15,000 or higher, werecommended the use of our oilfilter plant type 51 manufacturedby our principal MR Germany.

Filtering of switching oil allows toextend the inspection and oilchange intervals. Continuousfiltering also increases themechanical life of the diverterswitch by

Standard values for tap changer oil testing according to CIGREreport 12-13 (1982) apply to Transformer oil at servIcetemperature:

Use of Tap Changer Water content’) Dielectric strength”)

For use at the neutral point of windings <40 ppm > 30 kV/2,5 mmFor use at a position other than theneutral point of winding <30 ppm > 40 kV/2,5 mm

*) measured accorclng to IS 13567/1992

**) measured according to 156792/I 972

On-load Transformer Number of tap changetap changer rated current operations

M III 350 ≤ 350 A 100 000

M Ill 500 ≤ 350 A 100 000

≤ 500 A 80 000

MIII 600 ≤ 350 A 100 000

≤ 600 A 80 000

M1 351 ≤ 350 A 100 000

M1 501 ≤ 500 A 100 000

M1 601 ≤ 600 A 100 000

M1 802 ≤ 500 A 100 000

≤ 800 A 80 000

M1 1200 ≤ 800 A 80 000

≤ 1200 A 70 000

M1 1500 ≤ 1200 A 70 000

≤ 1500 A 60 000

M1 1800 ≤ 1500 A 60 000

≤ 1800 A 50 000

Table I Inspection Intervals

Note: 1. If Um >245 kV at the tapchanger the indicated numbers oftapchange operation must be halved &

2. regardless of the number of tap change operations listed inTable 1, inspection must becained out after 6 to 7 years

3. Regulation at the line end of the transformer with Um > 245

the first inspection must becanied out after 20,000 operationsor after 2 years of seniice respectively, which ever comesfirst

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ImmediateIy removing most ofabrasive particles responsible formechanical wear.

The user should regularly monitorthe transformer insulating oil in thetransformer according to theralevant standards.

If inspection is not carried out byE-MR personnel, please give usyour report to supplement ourin-spection data, incase of needrecommendation for the nextin-spection can be given.

WARNING : Inspections of thetap changer equipment areobligatory. Disregarding theInspection intervals canaffect the trouble-freeoperation of tap changer andtransformer.

1.5 Summary of inspectionworkA typical inspection includes thefollowing work:

— Withdrawing arid reinstallingthe diverter switch unit

— Cleaning the diverter switch oilcompartment and diverterswitch unit and, wherenecessary, the tap changer oilconservator tank.

— Changing the switching oil

— Checking the diverter switchoil compartment and diverterswitch unit

— Determining the contact wear

— Measuring the transitionresistors

— Checking the protective relay,drive shaft, motor drive unitand, where present; the oilfilter unit and voltage regulator.

The diverter switch unit should notbe exposed to air longer thannecessary (at max. for 10 hours).

Inspection work should not beinter-rupted. Care and cleanlinessshould be observed.

WARNING: inspection must becarried out by qualified,skilled personnel only. Theinstructions should befollowed strictly.

Damage which is foundduring inspection needsimmediate contact with E-MRfor assistance. Do not put thetap changer in service untilthe damage has beencorrected.

Do not alter or modify the tapchanger equipment withoutprior consulting E-MR.

Improper or incomplete workcarried out during inspectioncan aflect the trouble-freeoperation of tap changer andtransformer. Under certaincircumstances this can causeproperty damage andlorper-sonal injury.

2. Preparation2.1 Necessary equipment— empty vessels for dirty oil, the

necessary quantity of newtransformer oil for cleaning andoil change;

kV 36 72.5 123 170 245

Litres 125 130 150 170 190

Table II Oil filling quantity in litres

— an oil pump for draining andrefilling;

— a drip pan;

— miscellaneous brushes andabsorbent, non-fuzzing ragsfor cleaning;

— a work table;

— a lifting device:

— weight of diverter switch unitmax. 80 kg. required liftingforce is mdx. 1300 N;

kV 36 37.5 123 170 245

mm 830 870 1000 113 1230

Table Ill Withdrawal height in mm

— inspection tool

— spare parts

Please note: Lock tabs, selflock-ing screws and nuts shouldnever be used twice and shouldbe replaced during reassembly.

CAUTION: Always use E-MRauthorized replacementparts. Parts of other origincan affect the trouble-freeoperation of tap changer andtransformer.

2.2 Safety precautions

WARNING: The user of theplant should perform thefollowing safety measures.The transformer must beswitched off, isolated andsecured against reclosing. Allterminals must be groundedvisibly (by means of groundcables or ground switches).The working area should bemarked clearly.Start with inspection onlyafter all these safetyprecautions have beencarried out. Dis-regardingthem endangers lives2.3 Operating position whenwithdrawing the diverterswitch unit

The diverter switch unit can bewithdrawn in any operatingposi-tion. Take note of theoperating position whenwithdrawing the unit. However, werecommend on prin-ciple towithdraw the diverter switch in theadjustment position which ismarked by an arrow on theposition indicating disc of themotor drive unit.

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CAUTION: Do not operate themotor drive unit while the tapchanger is uncoupled, eithermanually or electrically. Toprevent electrical operationby remote control, it is goodsafety practice to isolate themotor drive unit by trIppingthe motor protective switch.

3. Withdrawal of theDiverter Switch Unit(FIg.4)

Lowering the oil level:Shut the stop valve between oilconservator and tap changerhead.

Lower the oil level in the tapchanger head. To do this, open thebleeder valve in the head cover(remove screw cap M30/wrenchsize 36, lift valve tappet by meansof a screwdriver) and the drainvalve.WARNING: The switching oilol the tap changer shouldalways be handled as a Ilam-mable liquid. Moreover,explosive gases canaccumulate under the tapchanger head cover, in theswitching oil or in the oilcom-partment. Therefore,strictly avoid open fire. Use apump-ing equipment suitablefor flammable liquids.

In case of an oil filter plant: openthe return pipe sample valve andoperate the filter unit, drain about10 litres of oil from the tapchanger head so that the supportplate is out of the oil (checkthrough the in-spection glass inthe head cover).Uncoupling the drive shaft ofthe upper gear unit:Unscrew 6 screws M6 (w.s.1 0)from the coupling. Take care notto lose coupling baits, nuts andlock tabs. Normally the drive shaftcan be moved to one side forclearance. It not, remove the othercoupling on the bevel gear fromthe square tube (screws, nuts andlock labs as above) until thehorizontal drive shaft can beremoved.Take off the tap changer headcover (fig. 5)Unscrew the cover bolts Ml 0.Take care not to lose springwashers. Remove the cover, takecare not to damage the Oringgasket of the head cover.

Dimantle In the following orderRemove the position indicatordisc (fig.6). Remove the clip fromthe shaft end. The coupling pinallows assembly in the correctposition only.

Fig . 4 Tap Changer head

1. Drive shaft ( square tube )2. Coupling brackets and bolt3. Upper gear unit (centric arrangement)4. Tap Changer head cover5. Bleeder Screw of head cover6. Pipe connection R for protective relay7. Pipe connection S with bleeder screw for suction pipe

54

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Take note of the marks on thetap changer head and thesupport plateIn the adjustment position the keyin the diverter switch drive shaft

matches with the triangle mark onthe support plate.

Undo the screws fixing thesupport plate.

Standard design: 4 screws MB x

20 (Fig. 7).

Special design for bell-typetransformer cover. 5 studs MBwith nuts (Fig.8).

In both cases take care of boltsor nuts and washers.

Carefully lift out the diverter switchunit using the lifting lugs (FIg.9)and put it on a flat, clean place.

4. Cleaning the OilCompartment, the OilConservator and the DiverterSwitch UnitOil compartment, oil conservator

Drain the oil compartmentcompletely. Open the stop valvebetween tap changer head and oilconservator. Drain oil from theconservator until clean oil flows.If necessary, flush the oilconservator tank with cleantransformer oil. Drain the oilcompartment, flush with clean oil,and drain again completely.

Diverter Switch UnitCarryout the visual inspection ofdivertor swithc external. Clean thediverter switch unit by flushingwith clean transformer oil.

5. Inspection of theDlverter Switch Unit

5.1 Withdrawal positionBefore starting the inspection takenote of the switched position ofthe diverter switch (=withdrawalposition). Note the position of thetrip lever of the spring energyaccumulator unit (Fig. 10) in orderto regain this position afterreassembly of the diverter switchunit.

5.2 Measuring the transitionresistor (Fig. 11)Measures the value of eachtransition resistor. The values arein the order of 0.3 ... 30 ohms.Measure at the open side of thediverter switch sector betweenthe stationary main switchingcontacts

Fig. 10Diverter Switch Unit

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and transition contacts above andbelow. For this purpose set thediverter switch to the oppositeposition by means of the operating

key Then measure again (Fig. 11).Compare the measured valuesagainst the indications on thenameplate.

A 10 percent difference ispefmissibie.

Detach the support cylinder. Undo8 screws M8.20 (w.s.1 3) eachwith a self-locking nut, at the 4fish-plates of the spring energyaccumulator. When removing thescrews take not to drop the partsinto the diverter switch.

Take off the support cylinder.

Take off the in outling drive shaftclean the support cylinder insideand outside with a brush and

transformer oil. Finally flush withtransformer oil and dry.

5.3 Removing the contactshells

Remove and reinstall contactshells consecutively on onediverter switch sector after theother.

To remove the contact shells thediverter switch must be set to itsmid-position where the transitioncontacts are closed:

Release the spring energyaccumulator and turn the driveshaft by means of the operatingkey until the wind-up sledge andthe cocking sledge have reacheda stable position just about in themiddle (fig. 12,13, 14).

Undo the fixing screws of thecontact shells of one diverterswitch sector: first the 4 otherscrews, then the 4 inner screws,in total 8 screws M6 x 20 (w.s.10), see fig. 15,16,17.

5.4 Removing the arc chutesWithdraw the arc chutesThe outer arc chutes have splitsidewalls and must be refitted inexactly their initial position.

Fig.11 Measurement of transition resistor on distinct points of the contact shells.

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5.5 Cleaning the diverterswitch unit

The contact shell with transitionresistors and stationary contactsystem must be cleanedthoroughly with transformer oil.Special care should be takenwhen cleaning insulating parts.Flush all parts with clean oil.Since the contact shells andtransi-tion resistors are to bedisassembled and reassembledone sector before the nextperform cleaning of the diverterswitch between theseprocedures.

5.6 Cleaning the diverterswitch Insulating driveshaft:

To remove the insulating driveshaft, the support cylinder withsupport plate have to be detachedfrom the energy accumulatorcase.CAUTION : Take care not todrop any parts Into thediverter switch. Otherwisethe diverter switch can blockand cause severe damage tothe tap changer andtransformer. There-fore, makesure that the number its iscomplete when disassemblingand reassem-bling) countthem to be sure.

5.7 Contact wear of mainswitching contacts andtransition contact

The admissible contact wear ofthe diverter switch contacts isdetermined by:

a. The contact volume (seetig.22). The max. admissiblecontact wear of the individualcontact is 4 mm.

Contacts should be replaced ifthis value is reached or expectedto be reached before the nextinspection.

b. the mechanical tap changeoperation sequence (see section1.1), shunt contact (A, B), mainswitching contacts (a, b),transition contacts (al, bl).

If the difference between mainswitching and transition contactscould become greater thancertain given limits, the correctmechanical switching sequenceof the diverter switch is no longerensured.

Unfavourable operatingconditions can cause increasedcontact wear on transitioncontacts.

Fig.21 Drive Shaft

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WARNING: Continuedoperation of the diverterswitch with greatly differingcontact layer thickness onarcing contacts can lead tosevere damage of tapchanger and transformer.

The max. permissible differenceof contact layer thicknessbetween main switching andtransition contact is 2.5 ... 2.6 mm.If this dif-ference has been

reached or is expected to bereached before the nextinspection, the contacts shall bereplaced or matched to the othercontacts by interchanging ormilling.

5.8 Determination of contactwear

Measure and note the thicknessot the contact layers on thestationary and movable main

switching and transition contactsby vernier gauge. Determine thecontact wear by comparing thedifference between new contactand measured value.

6. Replacement of theDiverter Arcing Contactsand Contact Braids

6.1 Diverter switch arcingcontacts

Each diverter switch sector isfitted with two main switchingcontacts (a, b) and two transitioncontacts (a1, b1). Each of thesecontacts exists as stationary anda movable contact.

Each stationary and movablecontact consists of two contacttips.

Replacement of the contact tipsof the stationary and movablecontact system is simple(attachment : 1 screw M6 for eachelement). Note the followingdetails:

Stationary contact(see tig.23, 24)

Each contact tip is fixed by onehexagon socket screw M6 x 16(w.s. 4 or 5), max. torque 9 Nm,locked by centre punching thegroove of the screw head.

Movable contacts(see fig. 25, 26, 27)

Each contact element is fixed byone hex head screw M6 x 16 (w.s.10), 2 dished washers, max.torque 9 Nm, locked by lock tab.

OLTC M III 350 M I 351:Before undoing contact tipsremove the contact braids on topand bottom (see section 6.2).

Note: In case of through-currentexceeding 200 A contacts oftungsten

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copper are used tor tne transitioncontacts (a1, b1).

OLTC M III 500, M III 600, M I 501,M l 601, M I 802, M I 1200, M I1500, M I 1800.

Before undoing the contact tipsremove the contact braids on top(see section 6.2).

6.2 Contact braids

The contact braids connect themain switching contacts andtransition contact of the movable

contact system to the slidecontact (= output terminal) of thediverter switch sector.

These braids are fixed by ascrew, washer and self-lockingnut (fig. 28, 29).

As a precaution, the contactbraids should be replaced after250,000 operations regardless ofreplacement of diverter switchcontacts.

Please note:

OLTC 111350, M 1351 (see fig.30)

There are 8 sets of contactbraids, two sets each on top andbottom as well as two sets of twoin the middle of a sector.

The contact braids of the mainswitching contacts and transitioncontacts are joined together at theoutput terminal.

2 sets ot contact braids (on topand bottom)

Each fixed to the output terminalby one bolt M6 x 28 (w.s.10) withself-locking nut and washer, max.

torque 9 Nm.

Attachment to the main switchingcontact (double braid) by one boltM6 x 18L, attachment to thetransi-tion contact (single braid)by one bolt M6 x 16.

All bolts with self-locking nut andwasher, max. torque 9 Nm.

4 sets of double contact braids(in the middle)

Attachment to the output terminal:

each by one bolt M5 x 22 (w.s.8)with self-locking nut and washer,max. torque 5 Nm.

Each fixed to the main switchingcontact by one bolt M6 x 1 BL(w.s.1 0) with selt-locking nut andwasher, max. torque 9 Nm.

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OLTC M III 500, M III 600, M I501, M I 601, M I 802, M I 1200,M I 1500 M I 1800 (sec fig. 31)

There are two sets of contactbraids on top only, connected tomain switching and transitioncontacts.

The contact braid of the mainswitching contacts and transitioncontacts are joined together at theoutput terminal.

Attachment to the output terminalby one bolt M6 x 28 (w.s. 10) withself-locking nut and washer, max.torque 9 Nm.

Attachment to the main switchingcontact and transition contact:

each by one bolt M6 x 16 (w.s. 10)with self-looking nut and washer.max. torque 9 Nm.

Always use new self-locking nuts.

7. Reattachment of thecontact shells

Reattach the contact shell inreverse order to removal. Thediverter switch is in the mid-posi-tion. Insert a chucking wedgebetween epoxy segment andcontact carder to hold back themovable contact system of thediverter switch.

This counters the pressure of themovable contact system (fig. 32.33) and makes attachment of thecontact shell easier.

Refit the arc chutes and makesure that they are properlyseated.

Attachment of each contact shellby 8 screws M6 x 20 (w.s. 10),max. torque 5 Nm, with look tabs(fig.34). Use new self-lockingscrews and lock tabs.

After tightening the screws,remove the chucking wedge inupward direction (fig.35).

When all contact shells have beenreinstalled, the spring energyaccumulator must be set from themid-position into a switchedposition of the diverter switch andlocked-in.

Insert a screwdriver betweenwind-up sledge and cookingsledge of the energy accumulator(fig. 36).

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Actuate the eccentric by meansof the operating key until the pawllocks-in (see fig. 37, 38).

Operate the diverter switchseveral times to check itsmechanical function.

Finally check again the transitionresistors as described in section5.2.

Set the diverter switch to itswithdrawal position (seesection 5.1).

The diverter switch unit is nowready to be reinstalled.

8. Reattach the supportcylinder with support plate:

8 bolts M8 x 20 (w.s.13), eachwith 2 washers, max. torque 22Nm. En-sure alignment of trianglemarks on bottom at the springenergy accumulator housing andon top at the support plate (fig. 39,40).

Operate the diverter switchseveral times to check itsmechanical function (fig. 41).

Final ly check again the transitionresistors as described in section5.2.

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Set the dlverter switch to Itswithdrawal position (seesection 5.1)

The diverter switch unit is nowready to be reinstalled.

9. Reinstallatlon ol thediverter switch unit

Remove the tap changer headcover.

Lift the diverter switch unit overthe open tap changer head. Lowerit down into the oil compartmentslowly and carefully.

When remounting the diverterswitch unit turn, if necessary, theinsulating shaft slightly until thecoupling engages.

Ensure alignment of marks on thesupport plate of diverter switchunit and in the tap changer head.

Fix the diverter switch unit by thescrews of the support plate.

Standard design: 4 screws MB x20 (w.s. 13).

Special design for bell-type tankinstallation: 5 nuts M8 (w.s. 13).

Both types secured by springwashers, max. torque 22 Nm.

Reinstall the position indicatingdisc (put on clip to shaft end).

10. Oil Filling

CAUTION: The tap changer oilcompartment arid theassociate oil conservatormust only be filled with newmineral insuIating oil fortransformers as per IEC 296(1982). The use of other oilcan affect the trouble-freeoperation of tap changer andtransformer.

Fill new oil into the diverter switchoil compartment up to the level ofthe support plate. Put the coveron the tap changer head makingsure that the gasket fits property;if necessary replace the O-ring.

The head cover is attached by 24bolts M10 (w.s. 17), max. torque34 Nm, secured by springwashers.

Open the stop valve betweenprotective relay and oilconser-vator. Vent the tap changerhead through the bleeder valve inthe tap changer head cover(remove screw cap M30 I w.s. 36and lift valve tappet by means ofa screwdriver).

Vent the suction pipe (screw capM161w.s 22. bleeder screw M6with chees head, max. torque 2Nm). see fig. 42.

Units with stationary oil filter unit:operate the oil fitter unit andbleed.

Fill up the oil conservator withnew oil to its original level.

CAUTION: The transformershould be energised notearlier than 1 hour after theoil filling.

11. Motor Drive

The on-load tap changer type Mis operated by motor drive unitMA2 mounted outside thetransformer tank, with maximumoperating posi. tion of 35.

The drive shaft is the mechanicalconnection between motor driveand tap changer head. The bevelgear connects the vertical andhorizontal parts of the drive shaft.The vertical part has to bemounted between motor driveunit and bevel gear, and thehorizontal part be-tween bevelgear and tap changer head.Thedrive shaft couplings are thesame for both parts. Both endsof the square shaft are connectedto the respective implement bytwo coupling brackets and onecoupling pin.

Square shaft have to be trimmedto the required lengths when theyare mounted on the transformer.

11.1 Coupling instructions

When mounting observe thefollowing instructions:

1. Check the shaft length betweenthe two shaft ends.

2. Attach the coupling brackets tothe shaft by “6” screws M6(wrench size 10) add flat washer(m6) and lock washer (m6). Slidethe coupling brackets on thesquare shaft as far as possible,tighten the M6 nuts. (maximumtorque 9Nm).

3. Lubricate “O” ring and couplingpin.

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4. Place the coupling pin into thetrunion and slide the square shafttogether with the coupling.

5. Provide the opposite trunionwith coupling bracket and couplingpin. Fit in the square shaft. Placesecond coupling bracket andtighten the “6” bolts (M6) with flatwasher, lock washer and (M6)nuts.

6. Make sure that there is an axialclearance of 2mm betweencoupling pin and couplingbrackets.

7. Finally tighten the couplingbrackets (max. torque 9Nm)placed on both side of the bevelgear and next to the tap changerhead.

Note: The screws of couplingbrackets next to motor drive unitmust be tightened and lockedwhen the rotation lag of motordrive has been equalized.

11.2 RotatIonal lagadjustment of the tapchanger and motor drive

For the following procedure thetap changer and motor drive mustbe the same tap position. Themotor drive has to be set to thesame position as found in the tapchanger.

Motor drive and tap changer canshowever, finally be coupled onlywhen the rotation lag (if there is

any) has been balanced. For thispurpose proceed as follows:

11.2.1Turn the hand crankclock-wise towards “Lower” untilthe energy accumulator of the tapchanger is released.

11.2.2Continue cranking andcount the revolutions necessarybr releasing the spring unit of themotor ‘drive, till a “click’ which canbe distinctly heard (about 3 to 5revolutions).

11.2.3Turn the hand crankcounter clockwise towards“Raise” until the energyaccumulator of the lap changer isreleased.

11.2.4Continue cranking andcount the revolutions, as in 11.2.1.

11.2.5Balancing the rotation lag isnecessary if the number ofclock-wise revolutions does notequal that of the counterclockwise revolu-tions. In thiscase the vertical part of the drivingshaft is uncoupled. The handcrank is then turned in the rotationsense which required morerevolutions to be effected. Thenumber of the balancingrevolutions amounts to half thedifference between the clockwiseand counter clockwiserevolutions.

Example(see Fig.43)

Turn the crank clockwise (e.g.from position 6 to 5) rotation lagdeter mined 3 revolutions(Fig.43). Turn the crank counterclockwise (e.g. from position 5 to6) rotation rag determined: 5revolutions. Uncouple. Equalizeby truning the crank for half thedifference:

1/2 (5-3) = 1 revolution counterclockwise. Recouple.

Checking the result:

Cranking clockwise (e.g. towardsposition 5) and then counterclock-wise (e.g. towards position6) results in both oases in thesame number of revolutionsconstituting the rotation lag (Ref.Fig.43).

EMR/OI/M/0010

type m tap changer

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