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 INVENTION
Improved Shunt Reactor with Auxiliary Windings
APPLICANT(S)
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S)
Patil Shubhangi of Crompton Greaves Limited, High Voltage Product Technology Centre, CG Global R&D Centre, Kanjurmarg (E), Mumbai -400042, Maharashtra, India; an 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 the field of shunt reactors and windings.
Particularly, this invention relates to the winding arrangement in shunt reactors.
Yet more particularly, this invention relates to sectional type windings arrangement in shunt reactors.
BACKGROUND OF THE INVENTION
A transformer is a device which transfers energy from one circuit to another. The transformer has a set of coils which perform this function. It is static equipment. The set of coils are conductors which are inductively coupled. The coils are a set of primary winding coils which are typically connected to a first energy source and a set of secondary winding coils to which the transfer of energy takes place. The windings are wound around a central core limb.
Like transformers, shunt reactors are vital part of the efficient operation of long transmission or AC cable high voltage power lines. The shunt reactor compensates the capacitive generation on power lines to avoid non-controlled voltage rise especially on lightly loaded lines. In remote areas, the power supply requirement necessitates the use of a three phase transformer. The transformer supplies power to a substation. But considering the limitation of remote areas and applications, it becomes essential to make a shunt reactor which can work as a transformer without disturbing its application of reactive power compensation.

Thus, the shunt reactors need to have two windings same as transformer. Shunt reactors contain the same components as power transformers, like windings, core, tank, bushings and insulating oil and are suitable for manufacturing in transformer factories. The main difference is the reactor core limbs, which have non-magnetic gaps inserted between packets of core steel.
These shunt reactors use shell type core construction with a laminated steel core with copper or aluminum windings. Core is CRGO laminated core made up of radially laminated packets. These packets are arranged one above the other by keeping air gap in between them as per the designed estimated air gap required for shunt reactor. Windings form an important part of shunt reactors. In a two winding shunt reactor two windings would be present. The one which is connected to a voltage source and creates the flux is called as a primary winding. The second winding where the voltage is induced by induction is called a secondary or auxiliary winding. Windings can be appropriately designated as High Voltage (HV) and Low Voltage (LV) windings. The winding with more number of turns will be a HV winding. The current on the HV side will be lower as V-I product is a constant and given as the VA rating of the machines. Also the HV winding needs to be insulated more to withstand the higher voltage across it. HV also needs more clearance to the core, yoke or the body. These aspects influence the type of the winding used for the HV or LV windings. Windings are of enamel coated copper conductors and wound in disc type arrangement.
The windings have a solid insulation of refined paper, and highly refined mineral oil is the insulating and cooling medium for the entire reactor. The insulation used in the case of electrical conductors in a transformer is varnish or enamel in dry type of transformers. To improve the heat transfer characteristics the conductors are

insulated using un-impregnated paper or cloth and the whole core-winding assembly is immersed in a tank containing oil. The oil thus has dual role. It is an insulator and also a coolant. The porous insulation around the conductor helps the oil to reach the conductor surface and extract the heat. The conductor insulation may be called the minor insulation as the voltage required to be withstood is not high. The major insulation is between the windings. Oil ducts are also used as part of insulation between windings. The oil used in the tank should be free from moisture or other contamination to be of any use as an insulator.
For the shunt reactor to work as a transformer, it needs two windings concentrically placed around a central limb of an iron core. Such shunt reactors have large voltage ratio and thus many times the non uniformity is observed in winding arrangement. Generation of electromagnetic field is inherent to proper transformer operation. The electromagnetic field inside the transformer leads to generation of short circuit forces in windings. In normal condition, these forces are relatively low but under short circuit condition, due to non uniformity in windings the forces becomes very large. The forces value depends on the flux lines between the windings. The flux lines are parallel to winding heights. Shunt reactors with two windings have larger ratio which results into unbalanced condition of windings with respect to winding height, winding radial thickness etc. It becomes very difficult to maintain the windings arrangement with uniform flux lines distribution. Thus to reduce the effect of generation of higher axial forces in windings, auxiliary winding with section type disc winding is used. Arrangement of sectioned type auxiliary winding with extra stiff insulation blocks between each section and strong radial support PCB blocks helps to minimize the axial forces and the effect of fringing to copper conductor.

JP60065507 discloses a closed magnetic circuit composed of an air gapped iron core and a closed magnetic circuit iron core and on a periphery of the main winding wound around a periphery of said air gap iron core, the auxiliary winding whose number of turns of winding is less than that of the main winding is wound concentrically with the winding. These windings are connected in series; then the number of times of winding of the auxiliary winding is selected in order to change the capacity of a reactor.
Further, JP 60160604 describes a 3-phase shunt reactor having a main winding and a secondary winding for power transformation. In this particular invention the main-windings are wound on an iron core leg having a gap, closely placed to the secondary winding. Herein, the main winding encloses the secondary winding. This winding arrangement is a continuous disc auxiliary winding.
Also JP601436I6 discloses, discloses a transformer consisting of primary windings and secondary windings wound around the core legs of the core, to which a shunt reactor can be connected as the secondary (load).
However, none of the above inventions discloses secondary or auxiliary winding which can control reactive power and also provide auxiliary power without affecting the reactor function. Also, there is a need for shunt reactors that reduces fringing flux which in turn reduces leakage flux and thus improves impedance. Thus, a need remains for an improved winding assembly in a shunt reactor which can act as transformer.

OBJECTS OF THE INVENTION:
An object of the invention is to provide an improved shunt reactor with auxiliary winding.
Another object of the invention is to provide a shunt reactor with better impedance.
Yet another object of the invention is to provide a shunt reactor with reduced reactor width.
Yet another object of the invention is to provide a shunt reactor with auxiliary winding having sectional disc winding which in turn reduces leakage flux.
Still another object of the invention is to provide a shunt reactor which can act as a transformer without disturbing the reactive power control function of shunt reactor.
Still another object of the invention is to provide a shunt reactor which can also act as a transformer.
SUMMARY OF THE INVENTION
According to the invention, there is provided an improved auxiliary winding arrangement in a shunt reactor with shell type core construction, said arrangement comprises:
a) a main winding wound concentrically over a central portion of a central limb; and

b) auxiliary winding made with a plurality of sections being attached together with stiff insulation blocks wound over said central limb and being electrically insulated therefrom.
Typically, said insulation blocks are interposed in a pre-determined manner such that to they maintain the auxiliary winding at equal height as main winding.
Typically, said insulation material can be made of materials selected from a group of materials consisting of Pre Pre-Compressed Board (PCB), nomex sheets or and the like.
Preferably, the thickness of the each of said insulation blocks is kept about 42mm.
Typically, said auxiliary winding is sectioned type disc winding with hard, solid insulation blocks between each section facilitates adapted to facilitate the flux to be in parallel lines, thereby minimizing the axial forces.
Typically, said auxiliary winding is sectioned auxiliary winding adapted to form said arrangement helps in order to reduce the effect of fringing direct to the conductor surface and to reduce the fringing flux lines by 2.5 times.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described in relation to the accompanying drawings, in which;
Figure 1 illustrates a complete view of a shunt reactor;

Figure 2 illustrates a sectional view of sectioned auxiliary windings;
Figure 3 illustrates a line diagram view of the winding arrangement of shunt reactor;
Figure 4 (a) illustrates a line diagram view of the effect of non-uniformity due to the unequal heights of the windings at one end on bending flux, according to the prior art;
Figure 4 (b) illustrates a line diagram view of the effect of non-uniformity due to the unequal heights of the windings at both the ends on bending flux, according to the prior art; and
Figure 4 (c) illustrates a line diagram view of the effect of uniform windings due to equal heights of both the auxiliary windings at both the ends on bending flux, according to the invention.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 illustrates a complete view of the shunt reactor.
According to the invention, there is provided a gapped iron core shunt reactor. (100) where the core is made up, typically, of thin CRGO M4 grade laminations of electrical steel to achieve the required reluctance of magnetic circuit. Shunt reactor comprises a core and coil assembly disposed in a protective tank (not shown), the core comprises at least one air-gapped central limb (11) placed between two lateral

limbs, in a spaced apart relationship therewith, the limbs are held vertically between a bottom yoke (4) and a top yoke (3), all made of magnetic material laminations. The winding assembly comprises a main winding (12) wound concentrically over auxiliary winding (13) where the auxiliary winding is wound over the central limb and is electrically insulated therefrom. The main winding over the auxiliary winding allows less insulation requirement as compared to the arrangement of auxiliary winding over main winding. Windings are, typically, of enamel coated copper conductors and wound in disc type arrangement.
Figure 2 illustrates the line diagram view of the shunt reactor with sectioned auxiliary winding.
In accordance with one embodiment of the invention, the auxiliary winding is made with various sections attached together with stiff insulation blocks (14) interposed in order to maintain the auxiliary winding at equal height as main winding. The provided insulation is kept as equal heights of air gap packets (18) and thus the air gap does not face the copper winding surface. The stiff insulation blocks facilitate minimized bending flux between main and auxiliary winding. The main winding can either be a continuous or sectioned disc winding. Additional extra end insulation is also provided to improve the critical current to a value beyond the short circuit current.
Also, there are provided radial supports added to the auxiliary windings to improve the mechanical strength.

Figure 4 (a) illustrates line diagram view of the effect of non-uniformity due to the unequal heights of the windings at one end on bending flux, according to the prior art.
Figure 4 (b) illustrates line diagram view of the effect of non-uniformity due to the unequal heights of the windings at both the ends on bending flux, according to the prior art.
Figure 4 (c) illustrates the line diagram view of the effect of uniform windings due to the equal heights of both the auxiliary windings at both the ends on bending flux, according to the invention.
Due to the non-uniformity in winding arrangement as seen in figure 4 (a) and 4 (b) of the prior art, axial forces on auxiliary windings tend to increase tremendously which causes increased bending flux lines (15).
However, sectioned auxiliary winding with hard, solid insulation blocks between each section facilitates the flux to be in parallel lines (16) thus minimizing the axial forces within limit Thus, the fringing flux near to air gap has minimum effect of fringing to copper conductor. This arrangement helps to reduce the effect of fringing and to reduce the fringing flux lines by 2.5 times which in turn helps in reduced axial forces on winding.
A single phase shunt reactor comprises one central limb and a three phase shunt reactor comprises three central limbs. Preferably, the winding assembly is wound over central limb.

While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. An improved auxiliary winding arrangement in a shunt reactor with shell
type core construction, said arrangement comprising:
a) a main winding wound concentrically over a central portion of a central limb; and
b) auxiliary winding made with a plurality of sections being attached together with stiff insulation blocks wound over said central limb and being electrically insulated therefrom.

2. An improved auxiliary winding arrangement in a shunt reactor as claimed in claim 1 wherein, said insulation blocks are interposed in a pre-determined manner such that they maintain the auxiliary winding at equal height as main winding.
3. An improved auxiliary winding arrangement in a shunt reactor as claimed in claim 1 wherein, said insulation material is made of materials selected from a group of materials consisting of Pre-Compressed Board (PCB), nomex sheets and the like.
4. An improved auxiliary winding arrangement in a shunt reactor as claimed in claim 1 wherein, the thickness of each of said insulation blocks is about 42mm.
5. An improved auxiliary winding arrangement in a shunt reactor as claimed in claim 1 wherein, said auxiliary winding is sectioned auxiliary winding with

hard, solid insulation blocks between each section adapted to facilitate the flux to be in parallel lines, thereby minimizing axial forces.
6. An improved auxiliary winding arrangement in a shunt reactor as claimed in claim 1 wherein, said auxiliary winding is sectioned auxiliary winding adapted to form said arrangement in order to reduce the effect of fringing direct to the conductor surface and to reduce the fringing flux lines by 2.5 times.