OLTC Technical Data

8/13/2019 OLTC Technical Data

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Technical Data General SectionTechnical Data TD 61

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NOTE

These technical data are intended for the calculator and designer of the transformer. This release replaces all previous releaseswhich then become invalid.Dimensional drawings and connection diagrams are subject to change without prior notice.

Drawings submitted during bidding and ordering are always binding.Since the on-load tap-changer is delivered to the specifications of the transformer manufacturer, the manufactureris responsible for selecting the correct properties of the on-load tap-changer so that the requirements of thetransformer are met.

This general section pertains to the following technical data.

VACUTAP VT ........................................... TD 124

VACUTAP VV ........................................... TD 203

VACUTAP VR ........................................... TD 237

OILTAP V ........................................... TD 82

OILTAP MS ........................................... TD 60

OILTAP M ........................................... TD 50

OILTAP RM ........................................... TD 130

OILTAP R ........................................... TD 115

OILTAP G ........................................... TD 48

DEETAP U ........................................... TD 51

Survey


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1 General .................................................................................................................................................................................................................. 5

1.1 How it functions .................................................................................................................................................................................... 5

1.2 Basic connections of the tap winding ............................................................................................................................................ 6

2 Characteristic properties of the on-load tap-changer ..................................................................................................................... 7

2.1 Designations of the on-load tap-changer .................................................................................................................................... 7

2.2 Through-current, step voltage and step capacity ....................................................................................................................... 10

2.3 Insulation ................................................................................................................................................................................................. 11

2.4 Overload .................................................................................................................................................................................................. 112.4.1 Through-currents greater than rated through-current .............................................................................................. 112.4.2 Operation at increased transformer power with improved cooling ....................................................................... 112.4.3 Required specifications for modes which are not defined by IEC 60354 or ANSI C57.91 ............................... 12

2.5 Short-circuit stress on on-load tap-changers and off-circuit tap-changers .................................................................... 12

2.6 Forced current division ........................................................................................................................................................................ 12

2.7 Permissible overexcitation .................................................................................................................................................................. 13

2.8 Multiple-column on-load tap-changers ........................................................................................................................................ 13

2.9 On-load tap-changer applications with variable step voltage............................................................................................... 13

2.10 Coarse tap winding/tapped winding, leakage inductance ....................................................................................................... 14

2.11 Potential connection of the tap winding ...................................................................................................................................... 14

2.12 On-load tap-changer in transformers for arcing furnaces (cf. also ordering sheets) ..................................................... 19

2.13 Installing the on-load tap-changer and off-circuit tap-changer ......................................................................................... 19

2.14 Activating the on-load tap-changer during the transformer test ........................................................................................ 19

2.15 Special applications .............................................................................................................................................................................. 19

2.16 Insulation oils ......................................................................................................................................................................................... 19

2.17 Service in arctic areas .......................................................................................................................................................................... 19

2.18 Hermetically sealed transformer with gas cushion .................................................................................................................... 19

2.19 Parallel jumpers for parallel connection of tap selector planes ............................................................................................ 19

3 Important information on design and installation ............................................................................................................................ 20

3.1 Designation of the terminal contacts of the tap selector and operating positions ........................................................ 20

3.2 Oil suction pipe ...................................................................................................................................................................................... 213.3 Oil filter unit ........................................................................................................................................................................................... 21

Table of Contents

Table of Contents


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Table of Contents

4 Protective relay RS 2001 ............................................................................................................................................................................... 21

5 Motor-drive units ED-S, ED-L ..................................................................................................................................................................... 22

5.1 Function .................................................................................................................................................................................................. 22

5.2 Type designations .................................................................................................................................................................................. 22

5.3 Technical data of the motor-drive unit ......................................................................................................................................... 23

6 Drive shaft ............................................................................................................................................................................................................ 24

7 Selecting the on-load tap-changer ............................................................................................................................................................ 24

7.1 Selection principle ................................................................................................................................................................................ 24

7.2 Examples of selecting the on-load tap-changer ......................................................................................................................... 25

8 Appendix ............................................................................................................................................................................................................... 28

Table of Contents


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1 General

1 General

1.1 Function principle

The on-load tap-changer provides uninterrupted voltageregulation of transformers under load. The voltage isregulated by changing the voltage ratio. This is done in steps.The transformer is equipped with a tap winding whosetappings are connected with the tap selector of the on-loadtap-changer.

This is the reason the on-load tap-changer is designed forimmersed installation in the transformer tank (fig. 1) to keep

the distances from the tap winding terminals to the tapselectors short. The on-load tap-changer is activated by amotor-drive. Drive shafts and bevel gear units mechanicallyconnect the motor-drive to the on-load tap-changer head.

Exception: The on-load tap-changer VACUTAP VT is fixed tothe active part of the dry-type transformer.

8997590D

Fig. 1 Transformer with on-load tap-changer, drawing

1 - On-load tap-changer2 Motor-drive3 Protective relay4 Oil conservator

Fig. 2aConnection principle of the on-load tap-changerconsisting of diverter switch and tap selector

On-load tap-changer (diverter switch-tap selectorprinciple)

The tap selector selects the desired tap which is then con-nected to the no-load side of the diverter switch. This tapthen accepts the service current with the next diverter switchoperation.

The functions of the diverter switch and tap selector aretime-correlated during the tap change, seefig. 2aforconnection principle.

KHW 370 - 4

Tap selector

Diverter switch


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1 General

1.2 Basic connection of the tap winding (see fig. 3)

For possible basic connections, see the technical data of thepertinent tap-changer type.

Fig. 3 Basic connections

a Without change-over selectorb With reversing switchc With coarse tap selector

a b c

KHW 114-4

On-load tap-changer (selector switch principle)

It combines the characteristics of a diverter switch and a tapselector. The change-over from one tap to the next takesplace in only one switching process, see fig. 2bfor connec-tion principle.

Fig. 2bConnection principle of the on-load tap-changer based onthe selector switch principle

EV1004


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2 Characteristic properties of the on-load tap-changer


2.1 Designations of the on-load tap-changer

Each type of on-load tap-changer is available in manydesigns, varying by number of poles, maximum ratedthrough-current, highest voltage for equipment Um, tapselector size, and basic connection diagram. For this reason,the designation of a certain on-load tap-changer modelmust also indicate these features (see fig. 4). This gives theon-load tap-changer an unique identification.

Number of steps and basic connection diagram

The tap selector can be extensively adjusted to the requirednumber of steps and the connection of the tap winding.The applicable basic connection diagrams are differentiatedby tap selector contacts (10 to 18), number of operatingpositions, number of mid-positions, and the change-overselector design. Fig. 5shows the designation of the basicconnection diagram.

The adjustment position is the position in which the on-loadtap-changer is delivered. The on-load tap-changer must be inadjustment position mode during maintenance work (re-moval or installation of the on-load tap-changer unit).

For further details, see the pertinent operating/maintenanceinstructions.Each design connection diagram of the on-load tap-changerexplicitly specifies the adjustment position.

The mid-position is the position in which the K contact isconnected in the reversing switch or coarse tap design.The mid-position is usually also the adjustment position (seedesign connection diagram of the on-load tap-changer).

1 mid-position: With 1 mid-position, there is no positionwith the same voltage before or after the K contact.

3 mid-positions: With 3 mid-positions, there is no change in

voltage before and after the K contact.Jumpered contacts are not considered as mid-positions.

Type

M I 601 123 / B 10 19 1 W

Basic connection diagram

Number of

poles Tap selector size

Max. rated

through-current in A

and additionalidentification of

the design

Highest voltage for

equipment Umin kV

Fig. 4Designation of the on-load tap-changerExample: On-load tap-changer, type M, 1-pole, max. ratedthrough-current 600 A, highest voltage for equipmentUm= 123 kV, tap selector size B, tap selector in acc. w. basicconnection diagram 10 19 1 W

10 19 1 W

Tap selector pitch Mid-position(s) Change-over selector

0

1

10 Max. 3 G W

12 operating positions Coarse Reversing

14 tap selector switch16

18

without change- with change-over

over selector selector

10 09 19

12 11 23

14 13 27

16 15 31

18 17 35

Fig. 5Designation of the basic connection diagram

Example:Tap selector pitch 10, max. of 19 operating positions,1 mid-position, change-over selector designed asreversing switch


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- / -

I

II

III

A

200

250300

350

400

500

600

800

1200

1500

1600

2000

2400

3000

1

2

3

Y

D

kV

36

40

72,5

76

123/76

123

145

170

245

300

362

B

C

D

DE

E

without change-over with change-over selector

9 VT

10 M, MS, R, RM, G, V, VV M, MS, R, RM, G, V, VV

12 M, MS, R, RM, G, V, VV M, MS, R, RM, G, V, VV

14 V, M, MS, R, RM, G V, M, MS, R, RM, G

16 M, R, RM, G M, R, RM, G

18 M, R, RM, (G) M, R, RM, (G)

22 M

without change-over with change-over selector

9 9

10 10 19

12 12 23

14 14 27

16 16 31

18 18 35

22 22

0

1

3W

G

1) Up to max. 107 operating positions (only type M)

OILTAPG

VACUTAPVT

VACUTAPVV

2 pole

x x

RI, GI

RI (forced current division)

RI

G

MI, RMI

OILTAPV

OILTAPM / MS

OILTAPR / RM

xxxx x xxx x xx xx xxBasic connection diagram

No. of poles

MI, RMI, RI, GI

M, MS, RM, R, G

MS, M, RM, R, G

VV

MS, M, RM, R, G, VIII Y

V, VV

No. of configured

sectors

(only 1-pole) 3 sectors

Application

Tap selector size

Not with selector switches and VACUTAPVV

R, G

M, RM

M, RM, R, G

M, RM, R

M, MS

On request

Um

1 sector

MS, M, RM, R, G,

V, VV

VT

Not for single-pole tap-changers

Application not with neutral point

Application with neutral point

2 sectors

MI, RMI; R

MI

M, RM, VV

M, VT I

3 pole

V (special design), VV

M, V

MSV (special design, not V I), VV

Reversing switch /

coarse tap 1)

1 mid-position

3 mid-positionsReversing switch

Coarse tap

0 mid-positions (without change-over selector)Mid-positions

Number of max.

operating positions

IUm

Type

V III D

Contacts

1 pole

V (not V I)


On-load tap-changer designations


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Off-circuit tap-changer designations

- -

Off-circuit tap-changer U

Number of poles III

300

600

800

1000

>1000

06

12

18

05

11

17Y

D

ME

MD

SP

YD

S

xxxx

Contact circle 750 mm,

max. of 17 operating positions



600 A

on request

1000 A

800 A



x x

Max. rated through-

current

Highest voltage for

equipment Um [kV]

3 poles

300 A

xx


xxx xx xx

17 operating positions

11 operating positions

5 operating positionsMax. number of

operating positions

Type of connection Linear off-circuit tap-changer for neutral application

Special connection

Linear off-circuit tap-changer for delta application

Single bridging off-circuit tap-changer

Double bridging off-circuit tap-changer

Series-parallel off-circuit tap-changer

Star-delta off-circuit tap-changer

Contact circle pitch

17.5

36

72.5

123

170

>170 on request


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2.2 Through-current, step voltage and step capacity

The through-currentis the current flowing through the on-load tap-changer and off-circuit tap-changer while in service.The through-current of an on-load tap-changer usuallyvaries along the voltage regulating range (e. g., while therated power of the transformer remains the same).The maximum through-current which a transformer canhandle continuously must be used for the rating of the on-load tap-changer and off-circuit tap-changer. This maximumcontinuously permissible through-current of the transformer

is the rated through-current Iuof the on-load tap-changeror of the off-circuit tap-changer.

The step voltage is the operating voltage between adjacenttaps. The step voltage can remain the same or vary over theentire setting range. If the step voltage varies, the maximumstep voltage Ustof the transformer is used to rate the on-load tap-changer and the off-circuit tap-changer.

The maximum rated through-current Iumvaries with thedesign and is the maximum through-current of an on-loadtap-changer and off-circuit tap-changer to which the cur-rent-related type tests refer.

Therated step voltage Uiof an on-load tap-changer is thehighest permissible step voltage for a certain value of therated through-current Iu. Together with a rated through-current, it is known as the related rated step voltage.

The max. rated step voltage Uimvaries with the design andis the max. permissible step voltage of an on-load tap-changer and off-circuit tap-changer.

The transition resistors of the on-load tap-changer are de-signed for the existing values of the maximum step voltageUstand the rated through-current Iu of the transformer forwhich the on-load tap-changer is to be used.

Since the permissible rated through-current Iuand thepermissible step voltage Ustvary with the value of the tran-sition resistors, these rated values refer to the particularapplication.

If an on-load tap-changer is to be used with values forstep voltage and through-current other than thosedeclared in the order (e. g., transformer power increased dueto improved cooling or use of the on-load tap-changer inanother transformer), MR must determine whether this ispossible or whether the transition resistors must be changed.

This also applies when the desired new rated values Iuand

Ustare below the original values since the design of thetransition resistors not only affects the switching capacitystress of the contacts but uniform contact wear is alsodesired.

Fig. 5 Rated step capacity diagram of a diverter switch1 - upper limit point2 - lower limit point

The rated step capacity PStNis the product of ratedthrough-current Iuand related rated step voltage Ui:PStN

= Iu x Ui

Fig. 5shows the typical load limits of a diverter switch.This means that the permissible range on the voltage side islimited by the max. rated step voltage Uimand, on thecurrent side, by the max. rated through-current Ium.

The points of the curve located between limit points 1 and 2are determined by the permissible rated switching capacity.The permissible switching capacity between limit points 1

and 2 corresponds to related pairs of values for Iuand Uiand may be constant or varying.

The rated step capacity diagram as well as individual valuesfor Iuand Uiin limit points 1 and 2 are specified separatelyfor each type of on-load tap-changer (see TD of the parti-cular type).

The limit step capacityis the greatest step capacity whichcan be safely transferred. Every MR on-load tap-changer canswitch at least twice the rated through-current Iuat stepvoltage Ustfor which the on-load tap-changer was designed.

This limit switching capacity is documented with the type

test as prescribed by IEC 60214. Tap change operations withcurrents greater than twice the rated through-current Iumust be prevented with suitable measures.

Iu

KHW 371-3

Ui = Uim

Iu = Ium

Ui



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2.3 Insulation

The insulation strength of the various insulation distances ofthe on-load tap-changer and off-circuit tap-changer is de-termined by the individual technical data of the particulartype of tap-changer. The specified rated withstand voltagesof the insulation apply to new, thoroughly dried insulatingmaterial in treated transformer oil (at an ambienttemperature of at least 10 C).

Selection of an on-load tap-changer and off-circuit tap-

changer requires the following information.- The maximum network-frequency voltages during service

- The power frequency test voltages occurring during thetransformer test

- The impulse voltages (lightning impulse, switching im-pulse, wave cut off at the back and wave cut off at thefront) occurring during the transformer test

The transformer manufacturer is responsible for the correctselection of the rated withstand voltages as required by on-site insulation coordination. The required rated withstandvoltages must be provided for the different insulation

distances.

- Against ground

- With multiple-phase types, between the phases

- Between contacts of one phase

The required specifications depend on the type of regulation(e.g., with on-load tap-changers: regulation without change-over selector, reversing switch arrangement, coarse tappingarrangement) and the type of tap-changer. The relevantinsulation distances and their relation to the voltages of thetransformer windings are described in the technical data of

the particular tap-changer type.

2.4 Overload

2.4.1 Through-currents higher than rated through-current

MR on-load tap-changers and off-circuit tap-changers canbe used for all transformer loads as described in IEC60354:1991 (Loading guide for oil-immersed transformers)and ANSI C57.91-1995 (Guide for loading mineral-oil-immersed transformers).

IEC 60354 differentiates between three modes.

- Normal cyclic loading

- Long-time emergency cyclic loading

- Short-time emergency loading

ANSI C57.91 differentiates between four modes:

- Normal life expectancy loading

- Planned loading beyond nameplate rating

- Long-time emergency loading

- Short-time emergency loading

Suitability of an on-load tap-changer for the above modes isdocumented with the type test in accordance with IEC60214-1989.

With normal cyclic loading or normal life expectancyloading mode, through-currents greater than the ratedthrough-current may occur during a daily load cycle. If theoperating conditions described by IEC 60354 or ANSI C57.91are adhered to (i.e., duration and power during a daily cycle,transformer oil temperature, and so on), this constitutesnormal service and not an extraordinary load. For thisreason, through-currents greater than the rated through-current which may occur briefly in the above modes do not

need to be given special consideration when selecting theon-load tap-changer.



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2.4.2 Operation at increased transformer load withimproved cooling

Keep the following points in mind when specifying therequired rated through-current of an on-load tap-changer.

When a transformer is run with different capacities due todifferent conditions (e.g., type of cooling, ambient temper-ature), the greatest load must be taken as the basis for therated power when selecting the on-load tap-changer.See also IEC 60076-1:1993. This is necessary since the oil

temperature in the transformer is not reduced despite in-creased transformer cooling due to the increased load and,in contrast to the transformer, the external conditions of theon-load tap-changer are not improved. Another reason isthe design of the transition resistors of on-load tap-changersbased on the greatest through-current so that the switchingcapacity stress on the contacts of the on-load tap-changer islimited to permissible values.

2.4.3 Required specifications for modes which are notdefined by IEC 60354 or ANSI C57.91

When asked about overload conditions, MR requests a

definition based on the above modes to avoidmisunderstandings and to clearly describe the conditions ofservice. If the requested mode cannot be defined in relationto IEC 60354 or ANSI C57.91, the following specificationsbecome necessary.

- Through-currents and related load duration during onedays cycle

- Oil temperature of the transformer during one days cycle

- Expected number of tap changes during the load phasesof one days cycle (only for on-load tap-changers)

- Duration of overload service in days/weeks/months- Frequency of this overload service (e. g., once a year or

rarely, only when other transformers fail)

2.5 Stress on on-load tap-changers and off-circuittap-changers due to short circuit

Permissible stress due to short circuits is listed below.

- Rated short-time withstand current as r.m.s. value ofpermissible short-circuit current

- Rated peak withstand current as highest permissible peak

value of the short-circuit current- Rated short-circuit duration as permissible short-circuit

duration during stress with rated short-time withstandcurrent

All MR on-load tap-changers and off-circuit tap-changersmeet at least the requirements of IEC 60214:1989 pertainingto short-circuit strength. Calculation of permissible short-circuit duration with stress of short-time currents lower thanthe rated short-time withstand current, or calculation of thepermissible short-time current for short-circuit durationslonger than the rated short-circuit duration is possible withthe help of the following equation.

Ix *tx= IK *tK

with

IK: Rated short-time withstand current

tK: Rated short-circuit duration

Ix: Permissible short-time current for

short-circuit duration tx(with t

x

always greater than tk)

tx: Permissible short-circuit duration for

stress with Ix(with I

xalways smaller

than Ik)

Due to the dynamic stress alone from the impulse current, animpulse current greater than the rated peak withstand cur-rent is not permitted. This is the reason that recalculation of

the rated values for higher impulse currents and short-timecurrents for shorter short-circuit durations is not permitted!

Short-circuit stresses usually occur only rarely on transfor-mers in service. With applications with very frequent short-circuit stresses (e.g., special test transformers), this must beallowed for by selecting an on-load tap-changer with greatershort-circuit resistance. Information on amount and fre-quency of the expected short-circuit stresses is necessary forthis.

2.6 Forced current division

With single-pole on-load tap-changers and off-circuit tap-changers for large rated through-currents, current paths areconnected in parallel. A distinction is made between applica-tions with and without forced current division.

Applications with and without forced current division withthe same rated through-current require different on-loadtap-changer and off-circuit tap-changer designs. The mean-ing of forced current division differs for on-load tap-chan-gers and off-circuit tap-changers.

On-load tap-changerDuring the change-over operation of the diverter switch,uniform division of the current on the parallel contacts must

be ensured. This always requires a divided tap winding and adivided main winding. Leakage impedance between theparallel main windings must be at least three times the valueof the transition resistor of the on-load tap-changer.



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It is imperative that MR be consulted about theseapplications. You will need a drawing of the completewinding arrangement with all parallel winding parts.

Off-circuit tap-changer:The tap winding must be completely divided. In addition,some windings on the tap winding next to the main windingmust also be divided.

In arrangements with forced current division, parallelcontacts may not be jumpered. The voltage between the

parallel tap windings when stressed with impulse voltagemust be considered. The transformer manufacturer mustspecify the required impulse voltage strength between theparallel tap windings.

2.7 Permissible overexcitation

MR on-load tap-changers meet the requirements of IEC60076-1:1993 (5% overexcitation) and ANSI IEEE C57.12.00-2000 (10% overexcitation) .

2.8 Multiple-column on-load tap-changers

Regardless of whether activated by one or more motor-drives, multiple-column on-load tap-changers (e.g., 3 x M I)do not switch synchronously. When delta connections with avery large regulation range and very low voltage in an endposition are regulated where the voltage can then only begenerated from a few taps, this can cause excessively highcirculating currents in the delta winding (varies with con-nection group and short-circuit impedance of the transfor-mer). In such cases, the transformer manufacturer mustspecify the circulating current for different positions of theon-load tap-changer in the three phases so that MR canconsider the required increased switching capacity when

selecting the on-load tap-changer and designing thetransition resistors.

2.9 On-load tap-changer applications with variablestep voltage

In applications with variable step voltage, the greatestpossible step voltage must always be specified for theselection of the on-load tap-changer. Examples of suchapplications include:

- Variable magnetic flow

- Tap windings with different numbers of turns

- Load and position-dependent step voltage for phase-shifter transformers

- Service under unusually great fluctuation of the systemvoltage

When different value pairs of step voltage and relatedthrough-current are required for an on-load tap-changer,the combination must consist of maximum step voltage andmaximum through-current within the permissible switchingcapacity range of the pertinent on-load tap-changer type,even when the step voltage and this through-current do notoccur at the same time.

Example:A transformer is being run at constant power within a largerange of fluctuating line voltage. Then the highest step

voltage occurs with highest system voltage together with alow through-current in relation to the transformer load, andthe greatest through-current occurs together with the loweststep voltage at the lowest system voltage.The on-load tap-changer must then be designed as if thehighest step voltage occurs together with the highestthrough-current.

The reason for this is the necessary adjustment of the tran-sition resistance to both the step voltage and the through-current. In general, the following applies to this adjustment:High step voltages require high values for the transitionresistance. In contrast, high through-currents require lowvalues for the transition resistance.Therefore, a solution to transition resistance adjustment isonly possible if there is a resistance value which is suitableboth for the highest step voltage and the highest through-current. Otherwise, the value of the transition resistance inthe above example would have to be continuously adjustedto the different system voltages.

There is always a suitable resistance value if the value pair ofhighest step voltage and highest through-current is withinthe permissible switching capacity. If this pair of values islocated just outside the permissible switching capacity range,MR must check individual cases to determine whether asolution for the adjustment of the transition resistance is stillpossible. When the permissible switching capacity range issignificantly exceeded, an on-load tap-changer type withgreater switching capacity must be used.



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2.10 Coarse tap winding/tapped winding, leakageinductance

During the change-over operation from the end of thetapped winding to the end of the coarse tap winding (mid-position, see fig. 6)and the reverse switching direction, allturns of the coarse tap winding and the entire tappedwinding are located between the selected and pre-selectedtap.With these switching operations, this results in a muchhigher leakage inductance for the circuit of the on-load tap-

changer as the internal resistance of the step voltage thanfor all other switching operations during which only theleakage inductance of a step takes effect and this induc-tance can be ignored for the function of the on-load tap-changer.

The leakage inductance described above for coarse tap wind-ing/tapped winding generates a phase shift between break-ing current and recovery voltage on the resistor contacts ofthe diverter switch which may cause longer arcing times.

This leakage inductance must be specified for adjustment ofthe on-load tap-changer to these operating conditions.

In extreme cases, this leakage inductance can be the deter-mining factor for selecting the on-load tap-changer type.

KHW 447-4

Fig. 6 Leakage inductance in the mid-position

Fig. 7 Standard values without tie-in resistors

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320

R, G

M, MS, RM

V V

V

Breaking current Is [mA]

RecoveryvoltageUw(

kV)

2.11 Potential connection of the tap winding

The tap winding is briefly galvanically isolated from the mainwinding during the change-over operation of the reversingswitch or coarse tap selector. It assumes a potential resultingfrom the voltages of the adjacent windings and the couplingcapacities to these windings or to grounded parts. This po-tential shift of the tap winding generates correspondingvoltages between the breaking change-over selector contactssince one contact is always connected with the tap windingand the other contact is always connected with the main

winding.This voltage is called the recovery voltage Uw. When thechange-over selector contacts open, a capacitive currentcaused by the above coupling capacities of the tap windingmust be interrupted. This current is called the breaking cur-rent Is. The recovery voltage Uwand the breaking current Ismay cause excessive discharges on the change-over selector.The permissible range of recovery voltage Uwand breakingcurrent Isis shown in fig. 7for the various on-load tap-changer types.

Without tie-in resistors



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Fig. 8 Potential connections

(Reversing switch is in mid-position)a Tie-in resistor Rpb With potential switch Sp

and tie-in resistor Rp

a Connection to potential of the tap winding by a per-manently installed ohmic resistor (tie-in resistor)

b Potential switchConnection to potential of the tap winding by aohmic resistor which is only inserted (by a potentialswitch) during the change-over selector operation.

The constructive solutions for a and b vary depending on thetype of on-load tap-changer. For additional details pertain-ing to our delivery program, see TD 48, TD 50, TD 60, TD 82,TD 115, TD 130, TD 203 and TD 237.

KHW 164-2

a b

If appropriate calculations result in values outside the per-missible range shown in fig. 7, the tap winding must beconnected to a fixed potential during the switching opera-tion. This is accomplished with the following measures(see fig. 8).

Due to the potential connection of the tap winding with atie-in resistor, the recovery voltage Uwis decreased on thechange-over selector contacts while the breaking current Isisincreased by the additional current via the tie-in resistor. Fig.9shows for the different on-load tap-changer types therange of recovery voltage Uwand breaking current Iswhichcan be used without consulting with MR when tie-in resistorsare used.This figure applies to all cases where the breaking current Isis primarily determined by the tie-in resistor.

With tie-in resistors

Fig. 9 Standard values for tie-in resistor, breakingcurrent Isprimarily determined by tie-in resistor.

Since the recovery voltage Uwand breaking current Isarenot the only important criteria for evaluating the permissibleswitching capacity of a change-over selector, an evaluationby MR is required when the ranges in fig. 7 and fig. 9areexceeded.

Since a decrease in the recovery voltage Uwdue to the tie-inresistor is always accompanied by an increase in the breakingcurrent Is, a solution with permissible change-over selectorcapacity cannot always be found for winding arrangementswith poor capacitive coupling. If this is true, a change-overselector with a higher permissible breaking current must thenbe used or the winding arrangement must be changed. This iswhy prompt examination of the change-over selector capa-city is particularly important for high-power transformers(i.e., large coupling capacities) and high operating voltages(i. e., great potential shift of the tap winding during change-over selector operation).

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320

Breaking current Is [mA]

V V

V

M, MS, RM

R, G

RecoveryvoltageUw(

kV)



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16 TD 61/02 061/02/01/0

Calculation of the recovery voltage Uwand the breakingcurrent Isas well as the design of the possibly necessary tie-in resistor can be handled by MR.

The following information is required for this.

- Winding arrangement (i.e., location of the tap windingwith respect to the adjacent windings)

- Capacitance of the tap winding to the adjacent windingsor capacitance of the tap winding against ground oradjacent grounded windings

- A.c. operating voltage across windings or the positions ofthe windings which are adjacent to the tap winding

In addition, the following information is needed todimension the tie-in measure.

- Expected stress due to lightning impulse voltage acrosshalf the tap winding

- A.c. voltage across half the tap winding under operatingand test conditions can usually be deduced from thenormal ordering specifications for the on-load tap-changers.

Example of the estimated calculation of the recoveryvoltage on the change-over selector

TransformerRated power: 13 MVAHigh voltage winding: 132 kV + 10%Delta connection: 50 HzTap winding with reversing switch(fig. 10)

Double concentric arrangement of the high voltage windingwith inside main winding (disk-type coils) and outside tapwinding (see page 17, fig. 11).Winding capacities:C1 = 1810 pF (between main and tap winding)C2 = 950 pF (between tap winding and ground)

On-load tap-changer:MS I 301/MS II 302 - 170/B-10 19 3 W

Fig. 10 Connection of the high voltage winding



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17TD 61/02061/02/01/0

Fig. 11 Winding arrangement with the related windingcapacities

as well as for voltage exceeding C1

and consequently, the vector variable and the correspondingabsolute value can be calculated as follows:

Core Tank

US OS

Fig. 12 Vectorial diagram for calculation of therecovery voltages on change-over selectorcontacts (+) and (-)

Assuming that winding capacities C1 and C2 are effective inthe middle of the winding, the following equation applies torecovery voltages Uw+and Uw-(see fig. 12below).



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18 TD 61/02 061/02/01/0

For C1 = 1810 pF C2 = 950 pF U1 = 132 kV UF = 13,2 kV

the following computational values result for the amount of recovery voltages UW+and UW-:

The breaking currents Is+und Isare:

Using the above number values, the following results:

Is+ = 63.97 mA

Is = 52.75 mA

Due to the high values for Uwa tie-in resistor is required.

After a tie-in resistor Rp = 280 k is installed, the following values are obtained:

Uw+= 19.6 kV Uw= 14.4 kV

Is+= 72.0 mA Is= 53.0 mA

Is--=.C2 + j .(C1 + C2)

U1 UF

2

U1

2 .3

Is+=.C2 + j .(C1 + C2)

U1 + UF

2

U1

2 .3



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19TD 61/02061/02/01/0

2.12 On-load tap-changer in transformers for arcingfurnaces (cf. also ordering sheets)

When in service, overloads of up to 2.5 times the ratedtransformer load occur in on-load tap-changers which areused in transformers for arcing furnaces. The on-load tap-changers must be adjusted to these operating conditions.

Types V V, MS, M, RM, R and G: The permissible step voltage isreduced for the required rated through-current to 80 % ofthe relevant rated step voltages specified in the applicable TD.

Type V: V 200 (250) is not designed for this type of service.With V 350 (400) the rated through-current is limited to200 A.

2.13 Installing the on-load tap-changer and off-circuittap-changer

The on-load tap-changer and off-circuit tap-changer mustbe installed vertically. The maximum deviation is 1.

2.14 Activating the on-load tap-changer during thetransformer test

When the transformer is excited, the on-load tap-changermay only be activated under rated frequency. This alsoapplies to no load service.

2.15 Special applications

Examples: High voltage direct current, generator operation,phase shifter, traction transformer, portion of the harmonicwaves > 10 %

Please see extra ordering sheet.

2.16 Insulation oilsTo fill the oil compartment and the related oil conservator,use only new mineral oil for transformers in accordance withIEC 60296 (specification for unused mineral insulating oilsfor transformers and switchgear) and IEC 60422 (supervisionand maintenance guide for mineral insulating oils in electri-cal equipment).

2.17 Service in artic areas

If on-load tap-changer oil temperatures of less than -25 Care expected, this must be specified on the ordering sheet sothat a temperature control can be provided for reliableservice. The temperature control consists of the thermosensor and the measuring amplifier. The thermo sensor isinstalled in the on-load tap-changer head cover. It recordsthe temperature of the oil in the on-load tap-changer.The measuring amplifier is installed in the motor-drive. It isconnected to the control current circuit so that the motor-

drive is blocked for electrical service when the temperaturecontrol is activated.

Remember that ambient temperatures below -45 C maydestroy the gaskets of on-load tap-changers and accessories.

2.18 Hermetically sealed transformer with gas cushion

This is available on request. Requests to MR for informationon implementation must contain the maximum gas cushiondensity below the transformer cover.

2.19 Parallel jumpers for parallel connection of tapselector planes

a) With forced current division:

Parallel jumpers are not permitted

b) With unforced current division:

Parallel jumpers on the tap selector terminals are stillmandatory even when the tap winding was wound in twoor more wires and each of these coil taps is connected asa tapping connection to the terminal contacts.

This reliably prevents the following:

Introduction of circulating currents into the current

paths of tap selector and diverter switch Arcing on movable tap selector contacts due tocommutation

Overvoltages between adjacent tap selector terminalsconnected in parallel

The parallel jumpers are also required to ensure the tie-inresistor takes effect for all parallel connected windingparts when tie-in measures are used.



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20 TD 61/02 061/02/01/0

Position 19 18 17 11 10 9 3 2 1

Current-carrying

selector switch 9 8 7 1 K 9 3 2 1terminal

Change-over 0 0 0 +selector connects

0 0 0 0 0 + 0 +

0 + 0 + 0 +

Operation Raise

in direction Lower

Hand crank Clockwiserotation Counterclockwise

Tap selector Counterclockwise

contact bridge Clockwise

Motor drive by motor contactor K2control by motor contactor K1

>>

>

< >

>


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21TD 61/02061/02/01/0

3 Important information on construction and installation

4 Protective relay

Fig. 14Suction pipe connection S and draining cockE = bleeding valve

3.2 Oil suction pipe

OILTAP on-load tap-changers are usually equipped with anoil suction pipe (see fig. 14) .

On-load tap-changer VACUTAP are equipped with suctionpipe connection S, but not with an oil suction pipe.

KHW 379-2

3.3 Oil filter unit

The oil filter unit is used to clean or clean and dry the switchingoil in the on-load tap-changer.The unit can be fitted with a paper filter (only for cleaning) or acombi filter (for cleaning and drying). For more information, seemanual BA 18.

4 Protective relay

For information, see manual BA 59.


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22 TD 61/02 061/02/01/0

5 Motor-drive units ED-S, ED-L


5.1 Function

The modularly designed motor-drive unit ED is used to adjustthe operating positions of on-load tap-changers/off-circuittap-changers in regulating transformers to the particularservice requirements.

The on-load tap-change operation is initiated by activatingthe motor-drive unit (single control pulse, from a device ofthe TAPCON series, for example). This tap changing opera-tion is always concluded regardless of whether additional

control pulses are output during the tap changing operation.Another tap change is not possible until all control devicesare at rest.

Fig. 15shows the switching sequence of an on-load tap-change operation.The dimensional drawings for motor-drive unit ED-S/ED-L(898801/898802) are listed in appendix 8.

Fig. 15 Switching sequence of an on-load tap-changeoperation

5.2 Type designations

The different basic designs of the ED motor-drive unit are identified with clear product designations.

Type designation Description Versions

ED100-ST Product designation Electric Drive

ED 100-ST Transmission gear design 100 = Small transmission gear (motor, 6.5 Nm)

200 = Large transmission gear (motor, 13/18 Nm)

ED 100-ST Protective housing design S = Small protective housing

L = Large protective housing

ED 100-ST Special applications = None

M = Monitoring

C = Plunger coil design

T = Voltage regulator TAPCON 240

MotorMotorMotorMotorMotordrivedrivedrivedrivedrive

TapTapTapTapTapselector

DiverterDiverterDiverterDiverterDiverterswitchoperation

Diverter switchDiverter switchDiverter switchDiverter switchDiverter switchcontactcontactcontactcontactcontactmovementmovementmovementmovementmovement

33 sections

Winding

KHW 220from KHW 938


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23TD 61/02061/02/01/0


5.3 Technical data of the motor-drive unit

The technical data apply to the standard design but may differ from the delivered model. Subject to change without priornotice.

Motor-drive unit ED 100/200-S/L

Motor power 0.75 kW 2.0 kW 2.2 kW

Voltage 3 AC/N 230/400 V

Current 1.9 A 5.2 A 6.2 A

Frequency 50 Hz

Synchronous speed 1500 1/min

Rotation of the drive shaft per switching operation 16.5

Running time per tap change operationg ca. 5.4 s

Rated torque of the drive shaft 45 Nm 95 Nm 130 Nm

Hand crank rotations per switching operation 33 54

Max. number of operating positions 35

Voltage of the controller and heater AC 230 V

Power consumption of the control current circuit(control/operation) 100 VA/25 VA

Heating capacity 50 W with ED 100/200 S 60 W with ED 100/200 L

Temperature range (ambient temperature) -30 C to +50C

Test voltage against ground 2 kV

Weight ED 100 S: 80 kg ED 200 S: 80 kgED 100 L: 130 kg ED 200 L: 130 kg ED 200 L: 130 kg


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24 TD 61/02 061/02/01/0

6 Drive shaft

7 Selecting the on-load tap-changer

7.1 Selection principle

Optimum technical and economic results are obtained byselecting an on-load tap-changer which just meets therequirements of the service and test conditions of thetransformer. Safety margins for the individual on-loadtap-changer data are generally not required.

To select the on-load tap-changer, the following importantdata on the transformer winding to which the on-load tap-changer will be connected must be available.

Data of the transformer winding

1 Rated power PN2 Connection (star-point, delta, single-phase connection)3 Rated voltage, setting rang: UN(1 x %)4 Number of steps, basic connection of the tap winding5 Rated insulation level6 Voltage stress of the tap winding during test with

lightning impulse voltage and induced a.c. voltage

The following values for phase values are calculated fromthe above for the on-load tap-changer.

Basic data of the on-load tap-changer

From 1, 2 und 3: Max. tapping current ImaxFrom 3 und 4: Step voltage UStSwitching capacity PSt= USt

.Imax

The suitable on-load tap-changer is determined by thefollowing characteristics.

Determination of the on-load tap-changer -1st step

On-load tap-changer typeNumber of polesMax. rated through-current

6 Drive shaft 7 Selecting the on-load tap-changer

For information, see manual BA 42.


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25TD 61/02061/02/01/0


7.2 Example of selecting the on-load tap-changer

Example 1 (for connection, see fig. 16)

We are looking for the right on-load tap-changer for athree-phase power transformer with the following data.Rated power PN= 80 MVA,Star connectionRated voltage and setting range of the high voltage windingUN= 110 (1 11 %) kV, 9 Stufen,Reversing switch

Rated insulation level of the high voltage winding forUp= 230 kV, 50 Hz/550 kV, 1.2|50

Voltage stress on the tap winding across the setting range ofone phase (250 kV, 1.2|50/16 kV, 50 Hz, 1 min.) between twophases of the tapped winding (220 kV, 1.2|50/24 kV, 50 Hz,1 min.)

On-load tap-changer data:

Imax= 80. 103/110 (1 11 %) .3 = 472 A

USt= 110. 103.11 % / 9 .3 = 777 V

PSt= 472.777 .103 = 367 kVA

If necessary, we recommend checking the followingspecifications of the on-load tap-changer.

Breaking capacity of the diverter switchTemporary overloadPermissible short-circuit currentContact lifespan of the diverter switch

Further designation of the on-load tap-changer inaccordance with TD 61/section 2.1 must be completed byspecification of the following characteristics.

Determination of the on-load tap-changer -2nd step

Highest voltage for equipment Umof the on-load tap-changerTap selector size

Basic connection diagramNote:The technical data for the above determinedon-load tap-changer must be used. See TD 48, TD 50,TD 60, TD 82, TD 115, TD 124, TD 130, TD 203 or TD 237.

110 (1 11 %) kV

KHW 376o-3Fig. 16


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26 TD 61/02 061/02/01/0

Determination of the on-load tap-changer:

1st step

In acc. w. table 1:::::On-load tap-changer type: MNumber of poles: 3Max. rated through-current: 500 AOn-load tap-changer design: M III 500 Y

On-load tap-changerM III 500 Y123/B10 19 1 W is selected

2nd step

In acc. w. TD 50/section 1.2 (Survey: Examples of designconnection diagrams):Umof the on-load tap-changer: 123 kVTap selector size: BBasic connection diagram: 10 19 1 W


InsulationConnection

Starconnection

Rated power,maximumtapping

current

80 MVA472 A

On-loadtap changer,change-over

selector

9 steps,reversing switch

Type, number of poles,rated through-current

M III 500 Y

Um, tap selector size

123 / B


10 19 1 W

to across theground setting range

550 kV 1.2I50 250 kV 1.2I50230 kV 50 Hz 16 kV 50 Hz

Rated voltage,setting range

110 (1 11 %) kV


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27TD 61/02061/02/01/0


110 kV

KHW 376u-3

220 (1 18 %) kV

Bild 17

Determination of the on-load tap-changer:

1st stepIn acc. w. table 1:

On-load tap-changer type: RNumber of poles: 3 x 1Max. rated through-current: 2000 AOn-load tap-changer design: 3 x R I 2002

2st stepIn acc. w. TD 115/section 1.2 Survey:

Examples of design connection diagrams:Ubof the on-load tap-changer: 110 kVUm(required): 170 kV Tap selector size: DBasic connection diagram: 12 23 1 W

On-load tap-changer data:

Imax= 600. 103/220 (1 18 %) .3 = 1920 A

USt= 220. 103.18 % / 11 .3 = 2078 V

PSt= 1600.1759 .103 = 3990 kVA

On-load tap-changer 3 x R I 2002170/D12 23 1 W is selected

InsulationRated power,

maximum

tappingcurrent

600 MVA1920 A

On-loadtap-changer,change-over

selector

11 steps,reversing switch

Type, number of poles

rated through-current

3 x R I 2002

Um, tap selector size

170 / D


12 23 1 W

Rated voltage,setting range

220 (1 18 %) kV

Connection

autotransformer

starconnection

to across the

ground setting range

550 kV 1.2I50 480 kV 1.2I50230 kV 50 Hz 49 kV 50 Hz

Example 2 (see fig. 17)

We are looking for the right on-load tap-changer for athree-phase current auto-transformer with the followingdata.:

Rated power PN= 600 MVA,Star connectionRated voltage and setting range of the high voltage windingUN= 220 (1 18 %) kV/110 kV, 11 steps,Reversing switch

Rated insulation level of the intermediate voltage windingfor Up= 230 kV, 50 Hz/550 kV, 1.2I50.

Voltage stress on the tap winding along the setting range480 kV, 1. 2I50/49kV, 50 Hz, 1 min.


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8 Appendix

Oil filter plant OF 100, dimension drawing ..................................................................................................................................................... 898718

Oil filter plant OF 100, control cabinet, dimension drawing ..................................................................................................................... 897688

Protective relay RS 2001, dimension drawing ................................................................................................................................................. 899084

Motor-drive unit ED-S, protective housing ...................................................................................................................................................... 898801

Motor-drive unit ED-L, protective housing ...................................................................................................................................................... 898802

Bevel gear CD 6400 .................................................................................................................................................................................................. 892916

Motor-drive unit ED-S, motor-drive unit ED-L, limit dimensions of the vertical drive shaft .......................................................... 898598

Electronic voltage regulator TAPCON 230, flush and projected panel mounting ............................................................................. 899564

Electronic voltage regulator TAPCON 240, 19-inch module rack ........................................................................................................... 899580

LED display panel, dimension drawing ............................................................................................................................................................... 899144

Position indicating instrument with square front frame, dimension drawing ..................................................................................... 897897

Position indicating instrument with rectangular front frame, dimension drawing and connection diagram ........................... 898105

Power supply unit for position indicator, dimension drawing ................................................................................................................... 898106

Digital remote position indicator, signal transmitter, dimension drawing ............................................................................................ 898699

Digital remote position indicator, 7-segment display, dimension drawing ........................................................................................... 899700

Digital remote position indicator, connection diagram ............................................................................................................................... 707281

Digital remote position indicator by selsyn transmitter, dimension drawing ................................................................................... 00711TM

8 Appendix


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29TD 61/02061/02/01/0

Oil filter plant OF 100

Dimension drawing8987182E


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30 TD 61/02 061/02/01/0

Oil filter plant OF 100

Control cabinet, dimension drawing8976882M


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31TD 61/02061/02/01/0

Protective relay RS 2001


Inspection

window

Identification label

GasketGasket

Cable gland

PG 16

Test push buttonsIN SERVICE OFF

(reset) (test tripping)

The arrow must always point towards the oil pipe leadingto the oil conservator of the transformer.

Plan view of test push buttons(cover removed)

1)NO - normally open, NC - normally closed, CO - change-over contact

The protective relay is to be connected in such a way that if it is energized, the power transformer is switched off immediately by the corresponding

circuit breakers.

Standarddesign

Specialdesignagainstsurcharge

0.65 -NO1 1.2 - NO A

3.0 - NO4.8 - NO

0.65 -NC2 1.2 - NC B

3.0 - NC4.8 - NC

0.65 -CO3 1.2 - CO C

3.0 - CO4.8 - CO

0.65 - 2NO4 1.2 - 2NO 2 A

3.0 - 2NO4.8 - 2NO

0.65 - 2NC5 1.2 - 2NC 2 B

3.0 - 2NC4.8 - 2NC

0.65 - NO + NC6 1.2 - NO + NC 1 A & 1 B

3.0 -NO + NC4.8 -NO + NC

Key of variants

Variant Arrangement of terminalsRelay designation1)Contact positions

In service Off

Design

Metal - dummy plug PG 16

Reed

contact


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32 TD 61/02 061/02/01/0

Motor-drive unit ED-S

Protective housing8988012E

Vertical guard plate with

spacing ring Hand crank

Wall of transformer tank

3 dummy plates for packing glands

special design with OLTC monitoring required

Shim

Attachment of protective housing

ca. 690 if opened 130


The cover can be opened

to the left or to the right

depending on the arrange-

ment of the hinge pins.

Aperture of fixing holes on protective housing

(rear view)

Aperture in protective housing for cables

(underside view)

* for design with

intermediate bearing


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33TD 61/02061/02/01/0

Motor-drive unit ED-L

Protective housing8988022E

Aperture of fixing holes on protective housing(rear view)

Aperture in protective housing for cables(underside view)

Vertical guard plate withspacing ring Hand crank

Wall of transformer tank

3 dummy plates for packing glands

special design with OLTC monitoring

required

Shim

Attachment of protective housing



The cover can be opened

to the left or to the right

depending on the arrange-

ment of the hinge pins.

* for design with

intermediate bearing


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34 TD 61/02 061/02/01/0

e1=205forstandarddesi

gn

e2=215fordesignwithballjoint

Bevel gear CD 6400



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35TD 61/02061/02/01/0

Motor-drive unit ED-S/ED-L with CD 6400

Limit dimensions of the vertical drive shaft8985980E


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36 TD 61/02 061/02/01/0

Electronic voltage regulator TAPCON 230

Flush and projected panel mounting8995640E

Clamp for

flush mounting

Remove crimp cable-entries for flush

mounting

Bracketing fishplatefor panel mountig

Panel cutout forflush mounting


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37TD 61/02061/02/01/0

Electronic voltage regulator TAPCON 240

19-inch module rack8995800E


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38 TD 61/02 061/02/01/0

LED display panel



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39TD 61/02061/02/01/0

Position indicating instrument with square front frame

Dimension drawing8978973M


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40 TD 61/02 061/02/01/0

Position indicating instrument with rectangular front frame

Dimension drawing and connection diagram8981053M


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41TD 61/02061/02/01/0

Power supply unit for position indicator

Dimension drawing8981062M


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42 TD 61/02 061/02/01/0

Digital remote position indicator

Signal transmitter, dimension drawing8986990M


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43TD 61/02061/02/01/0


7-segment display, dimension drawing8987000M


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44 TD 61/02 061/02/01/0


Connection diagram70728100


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Digital remote position indicator by selsyn transmitter

Dimension drawing00711TM


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Maschinenfabrik Reinhausen GmbH Phone +49 941 40 90-0Falkensteinstrasse 8 Fax +49 941 40 90-11193059 Regensburg, Germany E-Mail [email protected]

Documents

OLTC Technical Data