Siemens Traction Transformer

1
 Introduction

Ø The transformer is a static device, which transform power from one AC circuit to
another AC circuit at same frequency but having different characteristics

Ø These circuits are conductively disjointed but magnetically coupled by a common

time varying magnetic field

Ø It can raise or lower the voltage with a corresponding decrease or increase in

current.

2
 Technical Data

Ø Transformer type: EFAT 6144

Ø Key data:
ü Rated power: 1,250 / 2 x 625 kVA
ü Rated voltage: 25,000 // 2 x 950 V
ü Rated current: 50 / 2 x 657.7 A
ü Rated frequency: 50 Hz
ü Cooling oil: Mineral oil

Ø Main Standards:
ü The transformer has been electrically and thermally designed and checked in
accordance with IEC 60310.

3
Transformer details on the rating plate

Serial Number N311886

Type EFAT 6144
Standard IEC 60310
Cooling ODAF (Oil Directed air forced)
cooling
Rated Power HV - 1250 kVA
TW - 625 kVA
Rated Voltage HV - 25,000 V (22,500 V)
TW - 2 X 950 V (855 V)
Rated Current HV - 50 A (55.6 A)
TW - 2 X 657.7 A (2 X 730.8 A)
Rated Frequency 50 Hz

Total Mass 3000 Kg

Temperature raise Winding - 55 ℃; Liquid - 35 ℃

Max. Ambient temp. 50℃.

4
Overhead supply details

5
 Principle of Working

Ø In general principle of working of a transformer can be expressed on the basis of

law of electromagnetic induction as following:
ü When a conductor cuts the magnetic flux or magnetic flux cut the conductor, an emf is
induced in the conductor
ü The magnitude of this emf is proportional to the rate of change of flux.
E = dφ/dt
Where, E = emf
φ = flux

6
 Other Electrical specifications

Ø Layout of windings and main insulation

7
 Other Electrical specifications

Ø Layout of windings and main insulation

8
Transformer weight

9
 Construction

Ø Assembly:
ü An independent steel frame is used to press the iron core and winding together
ü The frame is fixed to the bottom of the tank by means of 4 bolts inserted into
4 threaded plates
ü The power from the overhead system is fed to the winding of the transformer through
an epoxy type bushing (only 1 HV bushing provided outside of main tank)
ü The secondary winding has 4 LV bushings with extension bus bars.

10
 Description of Operation

Ø Main components
ü Tank with active part fitted inside
ü Cooling system with oil pump
ü Oil conservator
ü The components given above are filled with cooling oil. The designation “Cooling oil”
refers to “Insulating and cooling oil” for mineral oils, silicone oils, ester or comparable
substances.

11
 Tank and active part

Ø The transformer tank and cover are steel construction

Ø The tank is adapted to the core with windings (active part)
Ø The tank is designed to carry the weight of the active part and the cooling oil
Ø It is also designed to withstand the accelerating forces occurring during operation

NOTE : The tank and conservator are not vacuum-tight

The maximum permissible overpressure (including oil column) is 0.3 bar.

12
 Tank and active part

Ø The iron core is a rectangular core with two limbs (which carry the windings) and
two yokes which connect the limbs
Ø The core is made from cold rolled grain-oriented transformer sheet steel which
has an insulating surface with high temperature stability
Ø The laminated sheets have been carefully cut, stacked and pressed to minimize
core losses and to keep noise generation to a minimum
Ø Both limbs are assembled without bolts
Ø High-grade end sheets are located at the top and bottom to ensure strength
Ø The limbs are covered with cast-resin impregnated glass-fiber tape
Ø The core limbs are connected with two yokes which are braced on both sides
with steel clamping frames.

13
 Cooling system with oil pump

Ø Circulating pump, pumps the cooling oil from the transformer through piping into
the cooling system and then back into the tank
Ø Forced cooling of the windings
Ø A suitable transformer protection concept must be implemented to ensure that all
cooling circuits are continually in operation and that the permissible temperatures
are not exceeded

NOTE : Exceeding the permissible temperatures will lead to a reduction in the

transformer’s service life.

14
 Oil conservator

Ø The expansion of the cooling oil due to changes in temperature is compensated

for by a conservator
Ø It is connected to the transformer via a supply line (hose, pipe)
Ø The volume of the conservator is sufficiently dimensioned to cover all possible
specified operating states
Ø This will also prevent the occurrence of any oil leaks when the transformer is
filled to the correct filling level for a particular operating state
Ø The air balance with the environment is achieved using a dehydrating breather

NOTE : The tank and conservator are not vacuum-tight. The maximum permissible
overpressure (including oil column) is 0.3 bar.

15
 Electrical connections

Ø a) HV Bushing:
ü Cast-resin-insulated connector bushing
type: 36 kV, 800 A
Ø Construction and operation:
ü The high-voltage side connection of the
HV - winding is constructed in the form
of a cast-resin-insulated bushing, plug-in
type bushing with outer cone (female
connector)
ü It is screwed to the tank wall with an
assembly flange ring
ü If the plug is not connected to the
bushing, the external cone of the
bushing has to be protected by a cap.
16
 Electrical connections

Ø b) LV Traction winding connections :

ü DIN - porcelain bushing. 36 kV, 800 A
Ø Construction and operation:
ü DIN bushings are available for the voltage series from 1 to 130 kV
ü They are made of a ceramic material and can be built in vertically, horizontally, or
angled position.

17
 Electrical connections

Ø c) Terminal box for protection

and control devices:

Ø Construction and operation:

ü The terminal box is designed to
protection class IP-67 and houses
the connections for all protection and
control devices.

18
 Electrical connections

Ø d) Oil circulation pump: Flowwell transformer oil pumps

are glandless monobloc type centrifugal pumps suitable for
circulating the transformer oil
Ø The pump has inline suction and delivery flanges
Ø The pumpset is driven by 3-ph, 50 Hz, 415 V AC supply
Ø It is compact and the construction is suitable for Traction duty
and outdoor application
Ø The unique design for these pumps ensures min imu m
maintenance and trouble free operation
Ø Motor HP: 2, Discharge in LPM 400, Speed 2850 RPM, class of
insulation H, Suction X delivery 70 X 70 mm & Total weight 32
kgs, Operating temperature range: -10 °C to + 120°C
Ø Before switching on the pump ensure that the pump is filled
with oil.

19
 How to start the oil pump

Ø First start-up:
ü Before starting up, always fill the circulating pump with oil
ü Bleed the air in the pump by means of venting screw
ü Make sure the pump turns in the right direction
ü The valves on either side of the pump and in the cooling circuit must be kept open
ü With the proper direction of rotation, the pump runs quietly and gives the rated
discharge at the specified head
ü No other pre start-up settings or test are necessary
Ø Maintenance:
ü The pumpset requires no special maintenance
ü The bearings get lubricated by the pumping oil itself.

20
 Dismantling of the pump

1. Close the butterfly valve on either side of the pump

2. Disconnect the pump from electrical supply. The connection bolts in the terminal
box are marked with U - V - W, same as the corresponding wires. Carefully withdraw
the supply cable in order not to damage the markings on the wire

3. Drain the oil from the pump by opening the venting and the draining screw. Drain
the oil into a clean and dry bucket (approx. 5 Ltr.)

4. Secure the pump against falling before removing the fastening screws

5. Loosen and remove the fastenings screws on both flanges of the pump

6. Remove the pump from the transformer.

21
 Mounting of the pump

1. Both butterfly valves for the pump are closed

2. Fit the pump with new gaskets

3. The draining and the venting screws of the pump must be closed
Maximum tightening torque: 18 Nm

4. Connect the electrical connections: Carefully insert the supply cable in order not
to damage the markings on the wire
Connect according to IEC: U/U1/L1 – V/U2/L2 – W/U3/L3 direction
The connection bolts in the terminal box are marked with U - V – W, same as the
corresponding wires.

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 Spare parts for oil pump

Ø Recommended spare parts for an operating period of 5 years:

S. No. Component Qty.

1 Bearing drive end 4304 A 2 nos

2 “O” rings 5 sets
3 Terminal block assembly 1 set
4 Stator lock bolt 2 nos
5 Drain and air plug 2 sets
6 Impeller locknut with washer and key 1 set
7 Circlip B52 1 no.

23
 Trouble symptoms and possible causes

Trouble symptoms Possible causes

Ø Motor does not start Supply failure
Loose Connection
Defective Phase

Ø Pumpset making noise Wrong direction of rotation

Defective bearings

Ø Insufficient pressure Wrong direction of rotation

Insufficient inlet to the pump

Ø Insufficient discharge Wrong direction of rotation

Insufficient inlet to the pump

Ø Pumpset draws more current Defective bearings.

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 Oil / Air cooler unit

Ø The aim of the cooling system is to transfer the electrical losses created within
the transformer to the outside air
Ø Two fans provide the necessary airflow to cool down the circulating oil through
the cooler
Ø The oil is pushed through the cooler by the circulating pump
Ø The cooler is designed as an aluminum plate cooler
Ø The cooler is mounted vertically in the cooling unit
Ø Two identical fan units consisting of a fan housing, a radial impeller, a bell mouth
and an electrical motor are fastened to the unit
Ø The sucking fans blow the cooling air to the track.

25
Vent / Drain oil cooler

26
Oil / air cooler Maintenance

27
 Insulating oil / Mineral oil

Ø The insulating and cooling oils are used to:

ü Insulate live winding parts and terminal leads from one another as well as from earth
ü Impregnate the paper insulation to increase its electrical strength and to prevent
flashovers between live parts
ü Extinguish any arcs occurring during flashovers
ü Absorb heat loss and transfer it to the cooling system
Ø Oils accepted:
1. Shell diala DX
2. Savita transformer oil to IEC 60296
These two oils are miscible
3. In case of other types of cooling oils are to be filled in, contact Siemens to approve.

28
 Oil level check

Ø The level of the cooling oil is checked on the oil level

indicator, which is mounted laterally on the conservator
tank
Ø The oil level must correspond with the temperature
mark
Ø For a proper oil level check, the transformer should be
in a horizontal position
Ø If the train / the transformer are not used for a longer
period of time, the oil level shall be checked at least
every 6 months
Ø If the oil level is lower than the corresponding
temperature mark, cooling oil has to be added to the
transformer tank
NOTE : If there is no oil level visible in the conservator,
the transformer must not be switched ON.
29
 Oil Topping up / filling process

Ø Topping up / filling of cooling oil can be performed by 2 different ways:

Ø a) By using the filling / cleaning opening on the top of oil conservator:

ü Remove the cover plate of the filling opening
ü Add the required quantity of cooling oil
ü Clean the gasket and dry the sealing surfaces. A damaged gasket must not be used
ü Mount the cover plate of the filling opening

Ø b) By using the oil filling / draining connection of tank bottom (if the oil
conservator top opening is not accessible)

Note : Always avoid ingress of water, moisture and dirt into the transformer at all
times.
30
 Oil Topping up / filling process

Ø Filling with an oil barrel:

ü The barrel has to be arranged at a level higher than the transformer tank
ü Connect a flexible hose between barrel and the tank
ü Vent the hose and fill the tank till the correct height is shown on the oil level indicator

Ø Filling with a pump:

ü Place the barrel beside the tank
ü Connect a flexible hose between pump and tank
ü Fill the tank till the correct height is shown on the oil level indicator.

31
 Cooling / Mineral oil sampling

Ø It is necessary to take samples from the transformer so that the breakdown

voltage can be measured
Ø Samples are also taken so that the chemical and physical properties of the
cooling oil can be checked
Ø The quality of the sampling determines to a great extent the usability and
consistency of the whole measurement
Ø Care must be taken to ensure that moisture, fibers and dust are kept away from
the samples
Ø The auxiliary equipment used for sampling and the equipment used at the
sampling point itself are to be thoroughly cleaned and carefully dried before use
Ø For sampling, the following filling/drainage point(s) on the transformer can be
used: Drain device “A40” as per DIN 42551
Ø SIEMENS recommends taking a cooling oil sample from the A40 drain plug with
the aid of a “F40” connector.
32
 Cooling / Mineral oil sampling

Ø Sample containers:
ü Either brown glass bottles or aluminum bottles with a volume of 1 liter is to be used
for the sampling, storage and transportation of cooling oil samples. The bottles must
also be clean and dry
Ø Guidelines for oil sampling:
ü The bottle is to be thoroughly rinsed immediately before sampling
ü The cooling oil used for rinsing must not be emptied back into the transformer;
instead it must be disposed of in accordance with government regulations
Ø Minimum details required for laboratory:
ü Transformer serial number
ü Date sample was taken
ü Type of cooling oil (mineral oil / ester / silicone oil etc)
ü Temperature of the cooling oil at the time of sampling.
33
 Protection and control devices

Ø Air Dryer / Breather with silica gel:

ü The dehydrating breather is attached to the conservator of
the transformer
ü Its task is to dry the air during temperature fluctuations
when the transformer is breathing as a result of the oil
expansion
ü Drying is achieved through the silica gel filling in the
dehydrating breather. The dehydrating breather protects
the insulation level of the transformer
ü The cooling oil can absorb moisture if the dehydrating
breather is not operational
ü Moisture reduces the electrical strength of the active part
and accelerates the thermal ageing of the transformer
insulation.
34
 Air Dryer / Breather with silica gel

Ø Maintenance: No maintenance required, periodically inspect for color of silica

gel, for Healthiness verification
ü Orange: Completely dry - Healthy
ü Colorless or Green : Completely saturated - Unhealthy
Ø The silica gel which has been replaced can be used repeatedly
Ø The silica gel containing moisture can be regenerated again by heating it to
approx. 130-150° C
Ø Drying is indicated by the change in color from colorless to Orange
Ø The silica gel is replaced as follows:
ü Remove the dehydrating breather
ü The used silica gel can be emptied through the opening in the flange respectively the
dry silica gel can be poured in
ü Clean the gasket. The gasket is to be replaced if damaged.
35
 Pressure Relief Valve / Device

Ø The pressure relief valve limits the

pressure in the transformer. As soon as
an overpressure of 0.6 bar is reached the
valve opens and cooling oil flows out
Ø At the same time a signal pin visually
displaying the opening of the valve is
pushed out
Ø The pressure relief valve shuts again once
the overpressure has been released
Ø The signal pin remains in the display
position and must be reset by hand. (It
must be pushed back into the original
position).

36
 PT 100 temperature sensor

Ø The temperature of the insulating and cooling oil

is measured by means of a resistance-type
thermometer
Ø The measuring sensor is arranged inside an oil
filled thermometer pocket
Ø The temperature is displayed indirectly via the
evaluation of the measured current which
changes due to the temperature-dependent
measuring resistors
Ø On reaching the maximum excess temperature
of the insulating and cooling oils the traction
output is reduced until the main switch is tripped.

37
 PT 100 temperature sensor

Ø Both temperature sensors PT 100 in the protective tube have a measuring

characteristic as per platinum resistance elements
Ø Basic tolerances for platinum resistance elements (Pt-100) as per DIN 43 760
are:
ü At 0 °C : 100.0 Ω
ü At 100 °C : 138.5 Ω
Ø Resistance can be measured at terminal of PT100 sensor using multimeter across
terminals of P1 & P2 junction as terminals are marked on terminal block
Ø Both elements resistance should be measured same. Considering the
temperature of mineral oil.

38
 PT 100 temperature sensor

Ø Replacing the thermometer:

1. Unscrew the cover on the thermometer
2. Remove the electrical connections from the sensor
3. Remove the resistance thermometer
4. Check whether the thermometer pocket has been filled two thirds with cooling oil
5. If the gasket is damaged, a new seal has to be fitted with the new thermometer
6. Install the new resistance thermometer and reconnect the electrical connections
7. Screw cover back on
8. Check that the thermometer is functioning correctly.

39
 Oil level Switch

Ø The oil level switch detects a decrease of the

oil level and operates an auxiliary contact
Ø If the oil level in the tank falls below cover,
t h e o i l l e v e l s w i t c h o p e ra t e s a n d t h e
tra n s for mer h a s to b e s witc h ed o ff t o
prevent damage
Ø After operation, the air trapped underneath
the switch has to be vented
Ø After each activation, the switch must be
vented by means of a venting screw that is
arranged on top of the connection flange
Ø Carefully loosen the screw, till the air is
pressed out. As soon as the oil is pressed out
without the formation of air bubbles, close
the screw.

40
 Oil level Switch

Ø Replacement:
ü Disconnect the control cable
ü Lower the oil level in the expansion tank: From the marking
for 20°C drain further 34 litres of oil to lower the level just
below cover. Drain the oil via the oil drain valve into a dry
and clean container
ü Loosen the 4 screws on the connection flange. Clean the
surfaces of the gasket area and fit new oil level switch. If
the gasket is damaged, replace with a new one
ü Fill the drained oil into the expansion tank via the filling and
cleaning opening on top of the expansion tank
ü Vent the switch by means of the venting screw of the oil
level switch
ü Test the function of the switch by means of pressing the
test button.
41
 Oil Flow Switch

Ø The oil flow sensor indicates the flow of the

cooling oil through the piping
Ø The fitted micro switch with changeover
contact is actuated by a movable paddle. The
freely movable paddle sits in and protrudes
from the stream of cooling oil
Ø If there is a flow of cooling oil the paddle is
moved to the display position
Ø If the flow velocity is too low or if there is no
flow of cooling oil, e.g. caused by failure of
the circulating pump, then the transformer
must be separated from the mains via the
main switch.

42
 Oil Flow Switch

Ø Replacement:
ü Disconnect the control cable
ü Place bucket underneath the flow sensor to collect the small quantity of oil dropping
out
ü Close the disc valve on either side of the sensor
ü Open the 4 screws of the mounting flange and carefully remove the sensor
ü Clean flange surfaces and gasket. If the gasket were found damaged, replace the
gasket
ü Only cooler serial numbers 1 to 24: fit the mounting ring and reassemble
ü Open both disc valves
ü Fill the small quantity of oil back into the expansion tank via the filling and cleaning
opening.

43
 Butterfly valves

Ø The butterfly valve enables either the circulating

pump or the cooler to be mounted or dismounted
without having to drain the entire insulating and
cooling oils from the system
Ø The butterfly valve remains tight (drip-tight)
during the relatively short time required for
mounting or dismounting
Ø An arrow indicates the open or closed position
Ø To operate the valve, lift the locking pin and turn
the axle with a spanner in the desired direction till
the pin locks in the final position
Ø In the open position, the valve is provided with
holes to fix a padlock
Ø The valve is built with an aluminum casing.

44
 Final checks

Ø We recommend checking the following points after the transformer has been installed:
ü Presence of any oil leakages
ü Position of butterfly valves in open
ü Rotating direction of the oil pump
ü Tightening torque of transformer fixing and Earthing of Tank
ü Tightening of all electrical connections
ü Bushings & Accessories connections tight
ü Paint
ü Oil level in the expansion tank
ü Silica gel in the breather
ü Functioning of the cooling system
Ø A protocol should be prepared to confirm that the checks have been carried out.

45
EMU/MEMU Transformer

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