FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
An intelligent cooling system for a transformer
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Sharath Nair of Crompton Greaves Ltd, Transformer (T2) Division, Plot No. Tl & T2, MPAKVN Industrial Area, Malanpur, Distt Bhind - 477116, Madhya Pradesh, India, Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

Field of the Invention:
This invention relates to cooling systems.
Particularly, this invention relates to an intelligent cooling system for a transformer.
Background of the Invention:
A transformer is an electrical device for transferring electricity from one circuit to another without use of moving parts. A transformer consists of two sets of winding; primary windings and secondary windings. Although there are no moving parts, the current rating and voltage rating of transformers, especially in industrial use, cause temperature rise in the conductors of the transformers. Moreover, this current rise causes mechanical stresses and generates pain points and fault points at various locations.
One of the primary concerns of any device in industrial use is to prolong maintenance and avoid breakdowns in order to continually strive to optimise throughput. Any breakdown, especially in the transformer, renders the entire set up or a factory or an assembly line useless.
These transformers feed different types of loads such as Domestic, Commercial, Agriculture, Industrial and the like. Hence, Distribution Transformers form the essential link between power utility and a large number of consumers. A

transformer is an expensive and critical equipment in electricity distribution network. Its outage due to failure causes immense inconvenience in network management and involves high expenditure on account of repair/replacement. Any Distribution Utility, therefore, takes all possible actions to reduce downtime / failure of transformers to a minimum and to extend their lives, at the most economic cost. Any breakdown, especially in the transformer, renders the entire set up or a factory or an assembly line useless. 10% of the total cost of a substation is attributed to the cost of the transformer. Transformer failure in India amounts to 15-25%, and alarmingly 30% of those fail when in warranty period. Most of these failures are due to overloading, oil leakage or the like causes.
In conventional transformers, conductors were used as windings with the tank filled with oil, which made the transformers bulky and huge.
An object of the invention is to provide an integrated device which includes an improved transformer along with an intelligent cooling system for maintaining the working parameters for efficient and continuous running of said transformer.
There is no device which incorporates the functionalities of a reduced size transformer with an inherent automatic cooling system.
Objects of the Invention:
Another object of the invention is to provide a maintenance-free transformer.

Yet another object of the invention is to increase the working reliability of a transformer.
Still another embodiment of this invention is to monitor the health of the transformer at all times.
An additional embodiment of this invention is to provide an automatic inherent cooling system to the transformer.
Yet another embodiment of this invention is to reduce the weight and size of the
transformer having an inherent cooling system.
*
An additional embodiment of this invention is to design a transformer system with increased working reliability.
Yet an additional embodiment of this invention is to provide a maintenance-free transformer.
Still an additional embodiment of this invention is to provide an automatic inherent cooling system to the transformer.

Another additional embodiment of this invention is to reduce the weight and size of a transformer.
Yet another additional embodiment of this invention is to monitor the health of the transformer constantly.
Summary of the Invention:
According to this invention, there is provided an apparatus with an intelligent compact transformer and an inherent automatic regulating cooling system, said apparatus comprises:
a. windings made of hollow metal tubes adapted to allow fluid flow through it,
said hollow metal tubes adapted to form windings of said transformer;
b. sensor means adapted to sense pre-defined parameters in relation to working
of said transformer;
c. first data storage means adapted to store sensed parameters;
d. second data storage means adapted to store threshold parameters;
e. pumping means adapted to pump coolant through said hollow metal tubes in
relation to sensed parameters in order to regulate temperature;
f. microprocessor adapted to receive sensed parameters and threshold
parameters and further adapted to compare said sensed parameters with said
threshold parameters to compute difference; and

g. control means adapted to control a range of pre-defined correction action in relation to computed difference and sensed parameter.
Typically, said hollow metal tubes are hollow copper tubes.
Typically, said sensor means includes sensor placement means adapted to place sensors ate pre-defined points in said apparatus
Typically, said sensor means includes parameter defining means adapted to define parameters in relation to points on said apparatus selected from a group of points consisting of fault-generation points, overvoltage measurement points, over-current measurement points, over-temperature measurement points, mechanical fault generation points, electrical fault generation points and the like points for ensuring a smooth, efficient and continuous working of said transformer.
Typically, said pumping means includes flow rate controller means adapted to control the flow rate of coolant depending upon computed difference.
Typically, said control means includes means to perform correction actions selected from a group of correction actions consisting of pumping the coolant through the hollow tubes, temporarily stalling the working of said apparatus, fixing faults through pre-defined logic, or pre-defined action of correction by contacting a remote location for aid.

Typically, said transformer includes low voltage coils ensconced within high voltage coils.
Typically, said transformer includes washer placed above and beneath said windings in order to appropriately place inlet outlet positions of said windings.
Typically, said transformer includes tie-rods to clamps said washers to said windings.
Brief Description of the Accompanying Drawings:
Figure 1 illustrates a schematic of the system;
Figure 2 illustrates a first step in the designing of said system; Figure 3 illustrates a second step in the designing of said system; Figure 4 illustrates a third step in the designing of said system;

Figure 5 illustrates a fourth step in the designing of said system and shows the Pump arrangement; and
Figures 6 and 7 illustrate Stress analysis on strip conductor.
Detailed Description of the Accompanying Drawings:
Figure 1 illustrates a schematic of the system of this invention.
According to this invention, there is provided an intelligent compact transformer with hollow windings and an inherent automatic regulating cooling system (100). In the prior art, conventional conductors were used as windings with the tank filled with oil, which made the transformers bulky and huge. In accordance with an embodiment of this invention, the transformer is made of windings (1) which are hollow metal tubes, typically, hollow copper tubes
Typically, said metal tubes are copper tubes. Use of copper tubes reduces the overall weight of the transformer and no or lesser oil used as coolant reduces the fire hazards as well.
In accordance with yet another embodiment of this invention, there is provided an array of sensors (5), said sensors being strategically located at pre-defined points of

the transformer, said pre-defined point being selected from a set of points consisting of fault-generation points, overvoltage measurement points, over-current measurement points, over-temperature measurement points, mechanical fault generation points, electrical fault generation points Eind the like points for ensuring a smooth, efficient and continuous working of said transformer. Typically, a heat-exchanger (2) controls the inlet and outlet temperature to the windings of said transformer.
In accordance with yet another embodiment of this invention, there is provided a data storage means adapted to store /read sensor data at discrete time intervals.
In accordance with still another embodiment of this invention, there is provided a pumping means (3) adapted to pump coolant (6) through hollow windings to regulate temperature if sensed data shows rise in temperature. It has a flow rate controller to control the flow rate of coolant depending upon intensity of breach of threshold value. Values relating to current and voltage may also be used to dynamically control the functioning of said pump to release coolant as a corrective measure.
In accordance with an additional embodiment of this invention, there is provided a microprocessor (4) adapted to receive sensed data which is stored from sensors into data storage means. Said microprocessor includes threshold values relating to sensed data for comparison. As soon as the threshold value is breached, one of the many pre-defined actions of correction may take place. One pre-defined action of

correction is to pump the coolant through the hollow tubes. Another pre-defined action of correction is to temporarily stall the working till normal working parameters are achieved or to fix any fault according to pre-defined logic. Yet another pre-defined action of correction is to contact a remote location for aid.
In this transformer, due to the proposed cooling arrangement, lesser or no oil is used; hence chances of getting burned are lesser.
Typically, an LV layer winding (1) made of metal tubes (copper tubes) is shown. The outlet of the winding (1) is attached to a non conducting material which further leads to a heat exchanger (2), power is tapped from the coil through a ring mechanism as is shown. The heat exchanger cools the coolant to a desired temperature and the coolant is again circulated to the pump (3). Sensor (5) attached to the winding provides inputs to the processor (4) through feedback loop 1 (FB 1). A processor (4) monitors the health of the system by monitoring the temperature rise of the winding (1) and the coolant (6), the processor (4) is programmed to vary the flow rate of the coolant according to the inputs through the feedback loop 1 (FB 1) and feedback loop 2 (FB2). The microprocessor checks coolant temperature and pressure (7). At a defined flow rate maximum cooling can be observed, hence with the change in loading conditions the defined flow rates are achieved. Hence transformer is able to withstand varied overload conditions.
Figure 2 illustrates a first step in the designing of said system.

In order to design a transformer in accordance with this invention, a generalised three dimensional model was developed for a multi-layer winding. This model was developed in a designing software system. The process to develop the transformer has been shown systematically, alignment of the windings, tap leads, pump forms the major part of the model and has been shown in a step by step approach, in Figures 2 to 5. The Low voltage and High voltage windings are coaxially placed as shown in Figure 2, reference numeral 12 represents inner Low voltage and reference numeral 14 represents outer High voltage coils. Typically a six layered HV and a two layered LV is shown.
Figure 3 illustrates a second step in the designing of said system.
Two cylindrical FG washers (16) are shown being placed on the coil, the washer having slots appropriately placed to keep the coil insulated and keep the coil outlet/inlet positions intact.
The washers are placed in such a way as to cover the winding completely radially and help 'keep the LV and HV outlets oriented at 180° opposition. These washers are then clamped to the coil by using tie rods (18) (as shown in Figure 4 of the accompanying drawings). This arrangement completes the Coil assembly of the transformer.
Figure 4 illustrates a third step in the designing of said system.
The figure is a model of coil assembly ready for core-coil assembly. The coil assembly is clamped tightly using FG rings to avoid any spring action of the coil.

Figure 5 illustrates a fourth step in the designing of said system and shows the Pump arrangement.
Reference numeral 22 represents the pump which is used to circulate oil inside the conductor. FG ring is shown by reference numeral 16, outlets of the windings are taken out through the FG ring. Power is tapped from the winding ends. Using nonconducting, high heat withstanding tube shown by reference numeral 24, coolant is circulated to the pump. Heat exchanger, though not shown in the figure, forms an essential part of the system.
The above parameters were modeled by making a prototype 500 VA single phase, forced oil cooled transformer with copper tube used as Low voltage winding, sensors were realized with a thermometer placed to detect the temperature variations, flow rate of the coolant was controlled by the use of a knob attached to the pump outlet.
The pressure that could be safely withstood by the wall thickness of the conductor was accordingly calculated using Hagen-Poiseuille and Darcy-Weisbach equations.
Heat dissipation and Pump flow rate calculation are further important designing aspects for the system of this invention.

For efficient working of the system, maximum heat produced in the system should be effectively removed and hence the system should be kept at a normal temperature, the flow rate of coolant being directly proportional to the heat dissipation from the conductor. But at the same time, care has to be taken so that at very high flow rates, because of turbulence and pressure in the coolant, the copper tube should not collapse nor should vibrations occur.
The heat to be removed from the winding is majorly the heat produced due to I R losses.
The amount of mass required to absorb the heat with respect to time can be found out. With a density of typically 0.8 gm/cm"5 the rate of flow of mineral oil can be calculated. For a pre-decided value of maximum allowable temperature, with change in rate of flow of coolant the temperature can be maintained.
Further calculations include Maximum wall thickness calculations.
At laminar flow, the vibrations caused and the pressure at the walls is at acceptable level. As the flow rate is dependent on the allowable volume of tube which is further dependent on the inner diameter of the tube and the amount of copper to be used is restricted by the current density. Hence an optimized value of inner diameter and wall thickness has to be found out. This is done by restricting the flow to laminar and hence calculating back the rate of flow. Typically, Hazen-Williams and Darcy-Weisbach equations are used. The theory has been assumed to work well with mineral oil as well. The Hazen-Williams equation is an empirical

formula which relates the flow of fluid in a pipe with the physical properties of the pipe and the pressure drop caused by friction.
Stress analysis calculations are done for the system of this invention.
To check the mechanical strength of a conventional conductor with respect to a tubular conductor, conductors of same area and properties were analysed.
Figures 6 and 7 illustrate Stress analysis on strip conductor.
Same amount of stress were applied to both the conductors with an area of 10 mm2 and a length of 100mm. The deflection in the conventional conductor is at a maximum value of 4.9 inches as shown in Figure 6 and that of tube conductor is 0.49 inch as shown in Figure 7.
Hence, it is observed that these conductors are mechanically much resistant to forces applied on them than a conventional conductor.

We claim,
1. An apparatus with an intelligent compact transformer and an inherent automatic regulating cooling system, said apparatus comprising:
a. windings made of hollow metal tubes adapted to allow fluid flow through it,
said hollow metal tubes adapted to form windings of said transformer;
b. sensor means adapted to sense pre-defined parameters in relation to working
of said transformer;
c. first data storage means adapted to store sensed parameters;
d. second data storage means adapted to store threshold parameters;
e. pumping means adapted to pump coolant through said hollow metal tubes in
relation to sensed parameters in order to regulate temperature;
f. microprocessor adapted to receive sensed parameters and threshold
parameters and further adapted to compare said sensed parameters with said
threshold parameters to compute difference; and
g. control means adapted to control a range of pre-defined correction action in
relation to computed difference and sensed parameter.
2. An apparatus as claimed in claim 1 wherein, said hollow metal tubes are hollow copper tubes.

3. An apparatus as claimed in claim 1 wherein, said sensor means includes sensor placement means adapted to place sensors at pre-defined points in said apparatus
4. An apparatus as claimed in claim 1 wherein, said sensor means includes parameter defining means adapted to define parameters in relation to points on, said apparatus selected from a group of points consisting of fault-generation points, overvoltage measurement points, over-current measurement points, over-temperature measurement points, mechanical fault generation points, electrical fault generation points and the like points for ensuring a smooth, efficient and continuous working of said transformer.
5. An apparatus as claimed in claim 1 wherein, said pumping means includes flow rate controller means adapted to control the flow rate of coolant depending upon computed difference.
6. An apparatus as claimed in claim 1 wherein, said control means includes means to perform correction actions selected from a group of correction actions consisting of pumping the coolant through the hollow tubes, temporarily stalling the working of said apparatus, fixing faults through predefined logic, or pre-defined action of correction by contacting a remote location for aid.

7. An apparatus as claimed in claim 1 wherein, said transformer includes low voltage coils ensconced within high voltage coils.
9. An apparatus as claimed in claim 1 wherein, said transformer includes washer placed above and beneath said windings in order to appropriately place inlet outlet positions of said windings.
10. An apparatus as claimed in claim 1 wherein, said transformer includes tie-rods to clamps said washers to said windings.