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
A Shunt Reactor APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Patil Shubhangi Sachin, Venkatasami Athikkam and Bhatia Anil Kumar, all of Crompton Greaves Ltd, Tl division, CG Global R&D Centre, Kanjur (E), Mumbai 400042, Maharashtra, India, all Indian Nationals
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 a shunt reactor. BACKGROUND OF THE INVENTION
Reactors are basic and integral part of distribution and transmission power system. Depending on their connections, they are connected in series and parallel. Reactors described herein, are usually connected in shunt from line to ground. Shunt reactors are mainly used for limiting voltage rise on long transmission lines at light load by supplying reactive power and compensating capacitive component, for limiting switching surges and for suppressing the harmonic contents. A remotely located substation is usually powered through a separate transformer connected to the EHV (extra high voltage) transmission line passing through the substation. Power requirement for such a substation is not very large. Therefore, there a shunt reactor(s) provided in the substations may be used for powering the substation instead of using the transformer. However, a conventional shunt reactor is designed only for inductively compensating the large capacitive reactive power in the transmission line. Such a conventional design being - providing a core and coil assembly, the core assembly having one or three air-gapped central limbs for a single or three phase reactor and pair of lateral limbs, all of which held between a top and bottom yoke; the coil assembly having windings wound over the central limb(s) and electrically insulated therefrom. One lead of the winding is connected to the transmission line and the other is grounded. Such a design needs to be changed for adapting the shunt reactor for performing the additional function of supplying power from the transmission line to low loads apart from performing its principle function -inductively compensating the large capacitive reactive power in the transmission line.

OBJECTS OF THE INVENTION
An object of the invention is to eliminate the use of a transformer for powering a remotely located substation.
Another object of the invention is to provide a shunt reactor which supplies power from the transmission line to low loads apart from performing its principle function of inductively compensating the large capacitive reactive power in the transmission line. DETAILED DESCRIPTION OF THE INVENTION
According to the invention, there is provided a shunt reactor comprising a core and coil assembly disposed in a protective tank, the core comprising at least one air-gapped central limb placed between two lateral limbs in a spaced apart relationship therewith, the limbs held vertically between a bottom yoke and a top yoke, all made of magnetic material laminations, and the coil comprising a main winding wound concentrically over a central portion of the central limb and electrically insulated therefrom; and a pair of auxiliary windings connected in series and wound concentrically over the respective end portions of the central limb and electrically insulated therefrom such that the main winding remains disposed between the auxiliary windings along the length of the central limb.
A single phase shunt reactor comprises of one central limb and a three phase shunt reactor comprises of three central limbs. Preferably, the main winding is wound over a majority area of the central limb and the auxiliary windings are wound over an equal area on the end portions of the central limb. The free winding lead of the auxiliary winding in top portion of the central limb is connected to a load and the free winding lead of the auxiliary winding in bottom portion of the central limb is connected to earthing.

These and other aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying drawings and appended claims, in which,
Fig 1 is a schematic cross-sectional view of a shunt reactor.
Fig 2 is a front view of the central limb of a shunt reactor depicting winding arrangement thereupon.
Fig 3 illustrates the electrical connection of the windings in the shunt reactor.
Referring to the drawings, a single phase shunt reactor comprises a core and coil assembly held in a protective tank (not shown). The core assembly comprises of a central limb 2 disposed between two lateral limbs 3 & 4, all of which are held between a top 5 and bottom 6 yoke. The core assembly is made up of a plurality of lamination sheets, made up of magnetic materials, stacked one upon the other. The central limb 2 is air-gapped in the known way by providing core packets along the length of the central limb at a regular interval. The coil assembly comprises of main winding 7 and a pair of auxiliary windings 8 & 9. The main winding 7 is wound concentrically over a central portion 10 of the central limb and electrically insulated therefrom by known means such as an electric grade insulating material tube placed between the windings 7 and central limb 2. The central portion 10 extends along a majority portion of the central limb 2. The auxiliary windings 8 & 9 are wound concentrically over the respective end portions 12 & 13 respectively of the central limb 2 and electrically insulated therefrom by known means such as an electric grade insulating material tube placed between the windings 8 & 9 and central limb 2. The auxiliary windings 8 & 9 are connected in series by connecting one leads thereof coming out near the main winding 7. The end portions 12 & 13 are of an equal size over which the auxiliary windings 8 & 9 are wound over. The main winding 7 is

electrically insulated from the auxiliary windings 8 & 9 adjacent thereto. As shown in Fig 3, the free lead of the auxiliary winding 8 on the top end portion 12 of the central limb 2 is connected to a load and free end of the auxiliary winding 9 on the below end portion 13 is grounded. One lead of the main winding 7 is connected to the transmission line (not shown) and the other lead is grounded.
In a three phase shunt reactor (not shown), the only difference in the construction being - three central limbs are provided instead of one. The main and auxiliary windings are wound over each central limb as described above. One winding lead of each main winding are connected to the three-phased transmission line and other winding leads are grounded. Either three single phase loads may be connected to the free winding leads of the auxiliary windings of the central limbs on the top portion of each central limb or a three-phased load may be connected to thereto.
The air-gaps may or may not be provided on the end portions of the central limb(s) on which the auxiliary windings are wounded. The ends portions may or may not be equal. According to a preferred embodiment, to compensate for the winding area of the main windings on the central limbs, the thickness of the main windings is increased on the central portion of the central limb(s). However, such depends on the design of the shunt reactor. The load may not be necessarily connected to the auxiliary winding on the top portion of the central limb only. It may be connected on the bottom portion as well with the free lead of the auxiliary winding on the top portion of the central limb being grounded.
According to the invention, power can be supplied to different loads through the auxiliary windings of the shunt reactor the just like through a transformer. Since the shunt reactor is anyways required in the substation, need of a separate transformer

to supply power to different loads in the power station is eliminated thereby saving a lot of cost on setting up the substation.
Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the scope of the invention as defined in the appended claims.

We claim:
1. A shunt reactor comprising a core and coil assembly disposed in a protective
tank, the core comprising
• at least one air-gapped central limb placed between two lateral limbs in a spaced apart relationship therewith, the limbs held vertically between a bottom yoke and a top yoke, all made of magnetic material laminations, and the coil comprising
• a main winding wound concentrically over a central portion of the central limb and electrically insulated therefrom; and
• a pair of auxiliary windings connected in series and wound concentrically over the respective end portions of the central limb and electrically insulated therefrom such that the main winding remains disposed between the auxiliary windings along the length of the central limb.

2. A shunt reactor as claimed in claim 1, wherein a single phase shunt reactor comprises of one central limb.
3. A shunt reactor as claimed in claim 1, wherein a three phase shunt reactor comprises of three central limbs.
4. A shunt reactor as claimed in claim 1, wherein the main winding is wound over a majority area of the central limb.
5. A shunt reactor as claimed in claim 1, wherein the auxiliary windings are wound over an equal area on the end portions of the central limb.
6. A shunt reactor as claimed in claim 1, wherein the free winding lead of the auxiliary winding in top portion of the central limb is connected to a load and

the free winding lead of the auxiliary winding in bottom portion of the central limb is connected to earthing.