FIELD OF THE INVENTION
The invention relates to a power transformer with improved cooling
harnessing tank mounted radiator banks. The cooling circuit of the 2 x 50%
radiator banks power transformer is associated with Radiator and Fans
involving 2 separate cooling groups each rated for 50% and above of the
total cooling capacity with optimum utilization and space.
BACKGROUND OF THE INVENTION
A Power transformer is generally immersed in mineral oil and housed inside
a metallic steel box known as Tank. By virtue of the working of the
transformer it results energy losses which are manifested as heat generated
inside the transformer. For a safe working of the transformer it is mandatory
to remove the heat generated to an extent so that the temperature of the
different parts of the core and coil assembly, supporting metallic structures
(inside the tank) are maintained below the safe limits. The surrounding oil
inside the transformer carries out this heat, which in turn gets heated. This
hot oil tries to go up by process of convection and enters the radiators.

Radiators are thin walled boxes with constriction (known as flutes) on
the surfaces, through which the hot oil enters from the transformer.
These are located outside the tank for oil flow and heat dissipation.
Hot oil form the top of the tank enters the radiators at the top. The
heat from the oil is dissipated through the thin metallic walls of the
radiator. The wall thickness of the radiator is in the range 1.0-1.2
mm. This thin wail of the radiator passes on the heat to the ambient
air. In this process, the oil of the transformer gets cooled and fed
into the transformer at bottom. This cold oil in-turn cools all the
parts of the core-coil assembly inside the transformer and the desired
temperature is maintained.
The oil from the tank Is taken to the radiators with the help of thick
metafile pipes, which can withstand the temperature and pressure of
oil. There are a number of ways of providing the radiator. In the
present Invention a novel method has been adapted in cooling
radiators in 2 groups, each comprising 50%s This is known as 2 x
50% cooling group. This arrangement enables the transformer to
remain in operation whenever 1 of the 2 banks undergoes

maintenance. To achieve this in the conventional method, the bank
of radiators are mounted on separate headers which are placed at a
distance from the tank. The headers are supported on a separate
structure know as "A-frame", which is grouted on-to the ground
using separately cast foundations. Hot oil from the top tank comes
out through a pipe, which gets branched into 2 different pipes, each
enter one header at the top, separately feeding each bank of
radiators. Separate pipes are provided at the bottom header to carry
away the cooled oil joined (in a T or F joint) to form one single oil
pipe which enters the tank at the bottom to supply cooled oils. In a
conventional arrangement the A-frame can be mounted along the
length (shown in Fig (1)) or the width (shown in Fig (2)). In the
event of replacing / removing the transformer in a conventionally
arranged 2 x 50 %radiator bank, the following activities are to be
done:
1. Complete radiator bank has to be evacuated
2. All the oil has to be stored in a separate vessel
3. The radiators are to be dismantled
4. The A-frames are to be removed

5. The foundation are to be de-cast
6. The transformer to be pushed out
7. The new transformer to be pushed in
8. The foundation of the "A - frame" are to be re-cast

9. The radiator and header assembly to be done
10. The oil removed is to be processed.
11. The oil is to be pushed back into the Radiator
12. The oil of the transformer to be mixed and circulated.
(**-the additional activities to be done for replacing / removal of
transformer, when the radiator banks are provided as shown in Fig
(2))
The major disadvantage in both the arrangements is that all the
aforesaid activities are required to be done for the replacement of the
transformer which results in extra costs to user. All these activities at
site take a long time resulting in loss of utility of the transformer and
idling of all other related equipment. In the case of hydro-power
stations, there is a loss of water too, which would have been
otherwise utilised for generation of electricity and which is, a direct
cost to user.
OBJECTS OF THE INVENTION
- The object of the invention is to develop an improved method of
oil-air cooling system for power transformer leading to higher
efficiency.

Another object of the invention is to provide a flexibility of easy
replacement of components for power transformers reducing shut down time
and cost.
Further object of the invention is to develop a compact system requiring
lesser space.
Also the object of this invention is to reduce the transmission loss of the
power transformer putting the same closer to the load centre with the
compact layout.
SUMMARY OF THE INVENTION
The present invention provides a power transformer with improved
cooling harnessing tank mounted radiator banks characterized in that the
independently

operative 2 x 50% radiator banks are directly mounted on the
transformer tank with the help of headers and connecting pipe, said headers
being terminated on a common bottom header terminating on a cooling pipe
so that hot oil from the tank can get cooled at the radiator banks and cool oil
from the radiator banks can be fed back to tank through the cooling pipe
connecting the bottom header and the tank thereby effecting saving in space
and cost and flexibility in maintenance.
The compact power transformer has been developed with improved cooling
system of 2 x 50% radiator banks, with lesser material and space
requirement having flexibility of easy replacement of components with least
shut down during maintenance jobs.
Due to compact size and lesser layout space, the transformer can be installed
closer to the load with less transmission loss.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
1. Fig. 1 shows the conventional transformer with cooling system mounted
along its length
2. Fig. 2 shows the conventional transformer and cooling system mounted
along its width
3. Fig. 3 shows the power transformer of the present invention and its
layout
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In the present invention for (2 x 50%) cooling system the said "A" frames :
(7) and their supporting structures as shown in Fig. i and Fig. 2 have been

eliminated and the radiators are directly mounted on the transformer as
shown in Fig. 3.
In the proposed method, two groups of radiator (3) are mounted on two
separate headers which are connected to the tank (1) directly.
Both the top header (2) are fed from the tank top at two separate locations
and interconnected by pipe (6). At the bottom, the two

group of radiators are terminated on one bottom common header which is
also mounted directly on the tank. The oil cooled by either of the headers is
collected by the bottom header and sent to tank (1) by the connecting pipe
(5).
As illustrated clearly in Fig. 3 of the drawings, hot oil goes from tank (1) to
top header (2) and enters radiator bank (3). Radiator bank is connected
between top header and bottom header. Oil cooled by radiator bank goes
from bottom header into the tank (1) through the connecting pipe (5).
In the improved system, when one bank is removed for operation or
maintenance, the valve for that bank is closed t the top and at the bottom and
the radiator is removed. The oil cooled by the other radiator gets into the
tank at two different locations through pipe connecting bottom header (5),
thereby cooling the transformer all around, while the cooling fan (4)
installed on the radiator brings in extra cooling effect on the system.

WE CLAIM:
1. A power transformer with improved cooling harnessing tank mounted
radiator banks (3), characterized in that the independently operative 2
x 50% radiator banks (3) are directly mounted on the transformer
tank (1) with the help of headers (2) and connecting pipe (6), said
headers (2) being terminated on a common bottom header terminating
on a cooling pipe (5) so that hot oil from the tank (1) can get cooled at
the radiator banks (3) and cooled oil from the radiator banks (3) can
be fed back to tank (1) through the cooling pipe (5) connecting the
bottom header and the tank thereby effecting saving in space and cost
and flexibility in maintenance.
2. The compact power transformer as claimed in claim 1, wherein said
radiator banks (3) are provided in two groups mounted on two
separate top headers (2) and connected to the tank (1) at two separate
locations therein through a bottom header and the connected cooling
pipe (5).

3. The compact power transformer as claimed in claims 1 and 2, wherein
both the radiator banks (3) are provided with valves at the top and
bottom allowing removal of one of the radiator banks for maintenance
purposes.
4. The compact power transformer such as herein described and
illustrated in the accompanying drawings.

ABSTRACT

A COMPACT POWER TRANSFORMER WITH AN IMPROVED
2 X 50% RADIATOR BANKS
A compact power transformer with an improved 2 x 50% radiator banks
(3) directly mounted on the transformer tank (1) with the help of headers
(2) and connecting pipes. The headers (2) are terminated on a cooling
pipe (5) so that oil from the tank (1) can get cooled at the radiator banks
(3) and cool oil from the radiator banks (3) can be fed back to tank (1)
through the cooling pipe (5).