FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
An improved three-phase disconnector.
APPLICANT
Crompton Greaves Limited, CG House, Dr. Annie Besant Road, Worli, Mumbai -400030, Maharashtra, India, an Indian Company
INVENTOR
Kerssebeeck Bert Leonard, Hammel Eamonn Brendan, Mulcahy Eamonn Brendan of CG Power Systems Ireland Ltd., Distribution Transformer Division T7, Dublin Road, Cavan, Ireland, all Irish Nationals; Van Schevensteen Raymond of CG Power Systems Belgium N.V., Distribution Transformer Division, Antwerpsesteenweg 167, Mechelen, Belgium, Boets Rene of Lemanstraat 21 -B2860 Sint Katelijne Waver - Belgium, both Belgian 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 the field of electrical and electronics engineering. Particularly, this invention relates to the field of Power Systems. More particularly, this invention relates to the field of three-phase disconnectors. Specifically, this invention relates to an improved three-phase disconnector.
BACKGROUND OF THE INVENTION
The term switchgear, used in association with the electric power system, or substation or power grid, refers to the combination of electrical disconnectors, fuses and/or circuit breakers used to isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream. This type of equipment is important because it is directly linked to the reliability of the electricity supply and the electrical load.
A disconnector, or an isolator, is a switchgear equipment adapted to electrically disconnect an electrical circuit / assembly / component / device. This disconnection requirement may occur during service or maintenance periods when it is required that the electrical circuit / assembly / component / device is completely de-energised. This disconnection requirement may also be occur in cases of fault detection or surge detection or any such pre-defined parameter detection which may potentially harm the electrical circuit / assembly / component / device.
Disconnectors are often found in electrical distribution and industrial applications where machinery must have its source of driving power removed for adjustment or

repair or interruption of any kind. High-voltage isolation switches are used in electrical substations to allow isolation of apparatus such as circuit breakers and transformers, and transmission lines, for maintenance.
Typically, disconnectors find their application in three phase distribution transformers in the range of 50 to lOOOkVA - having an integrated disconnecting and self-protecting device as described in IEC 60076-13 and also known as "TPC" (French abbreviation for "Transformateur Protection Coupure") used in pole-mounted, cabin-mounted and substation-mounted ("PRCS") transformers.
According to the prior art, typically, 2- or 3-phase disconnectors are used which do not guarantee three phase disconnection in all cases of fault scenarios, leaving one phase still live and therefore are not acceptable anymore for certain standard regulatory bodies.
Hence, there is a need for an improved disconnector which guarantees a three-phase disconnection in all fault scenarios.
OBJECTS OF THE INVENTION
An object of the invention is to provide a three-phase disconnector.
Another object of the invention is to provide a quick-response three-phase disconnector.
Yet another object of the invention is to provide an efficient three-phase disconnector.

Still another object of the invention is to provide a three-phase disconnector which reduces maintenance costs.
An additional object of the invention is to provide a three-phase disconnector which is a fail-proof disconnector.
SUMMARY OF THE INVENTION
According to this invention, there is provided an improved three-phase disconnector, said disconnector comprises:
a) three horizontally mounted current limiting fuses, each of said fuses individually being connected to one phase of a three-phase power supply line and further comprising three corresponding striker pins adapted to axially move in an operative first direction upon detection of an overcurrent fault;
b) three sliding contacts coupled to said three striker pins, correspondingly, each of said sliding contacts adapted to axially slide in said first direction upon activation of said corresponding striker pin;
c) three stationary contacts placed substantially collinear to said three sliding contacts; correspondingly, in a spaced apart manner and adapted to be partially overlapping in its non-operative state and further adapted to be more than said partially overlapping in its operative state;
d) winding wires being placed in between said sliding contacts and said stationary contacts such that a single wire (one per each phase) is passed through said spaced-apart region between a corresponding sliding contact and a corresponding stationary contact;
e) spring loaded plungers adapted to receive said winding wires, correspondingly; and

f) vertical insulation tubes adapted to receive said spring loaded plungers when they fall down once said winding wires are cut by said contacts.
Typically, said sliding contacts are mounted in a staggered motion of a pre-defined distance in order to reduce the force needed to cut said wires.
Typically, each sliding contact is a sliding blade.
Preferably, each sliding contact is a sliding ceramic blade.
Typically, each sliding contact is a blade with a V-shaped operative front groove with blades etched in the internal arms of the V-groove.
Typically, each stationary contacts is placed on a housing such that it lends bottom support to the stationary contacts and keeps the operative edge of the stationary contacts free in order to receive a wire.
Preferably, each stationary contacts is placed on a nylon (or similar isolating synthetic material) housing such that it lends bottom support to the stationary contacts and keeps the operative edge of the stationary contacts free in order to receive a wire.
Typically, said stationary contacts are mounted in a staggered motion of a predefined distance in order to reduce the force needed to cut said wires. Typically, each stationary contact is a sliding blade.
Preferably, each stationary contact is a sliding ceramic blade.

Typically, each stationary contact is a blade with a V-shaped operative front groove with blades etched in the internal arms of the V-groove.
Typically, said sliding contacts are coupled contacts such that each contact is simultaneously activated when a fault on one phase (i.e. at one striker pin fuse) is detected and hence, wire is cut individually within milliseconds of each other to reduce the force needed by the blown pin striker fuse.
Preferably, said wires are blank or enameled copper or aluminum wires.
Typically, said spring loaded plungers are housed inside vertical insulation tubes which receive said winding wires.
Preferably, said spring loaded plungers are brass or copper plungers.
Typically, said wires are soldered or screwed into said spring loaded plunger, correspondingly.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates atop isometric view of the disconnector;
Figure 2 illustrates a close-up side view of the disconnecting mechanism (blades) of the disconnector;

Figure 3 illustrates a close-up front view of the disconnecting mechanism (blades) of the disconnector;
Figure 4 illustrates a front view of the disconnector;
Figure 5 illustrates a portion plunger component of the disconnector;
Figure 6 illustrates another close-up front view of the disconnecting mechanism (blades) of the disconnector;
Figure 7 illustrates a close-up top isometric view of the disconnecting mechanism (blades) of the disconnector;
Figure 8 illustrates a close-up top view of one phase of the disconnecting mechanism (blade) of the disconnector; and
Figure 9 illustrates a close-up side view of the three phases of the disconnecting mechanism (blades) of the disconnector.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
According to this invention, there is provided an improved three-phase disconnector (100).
Figure 1 illustrates a top isometric view of the disconnector.
Figure 2 illustrates a close-up side view of the disconnecting mechanism (blades)
of the disconnector.

Figure 3 illustrates a close-up front view of the disconnecting mechanism (blades) of the disconnector.
Figure 4 illustrates a front view of the disconnector.
Figure 5 illustrates a portion plunger component of the disconnector.
Figure 6 illustrates another close-up front view of the disconnecting mechanism (blades) of the disconnector.
Figure 7 illustrates a close-up top isometric view of the disconnecting mechanism (blades) of the disconnector.
Figure 8 illustrates a close-up top view of one phase of the disconnecting mechanism (blade) of the disconnector.
Figure 9 illustrates a close-up side view of the three phases of the disconnecting mechanism (blades) of the disconnector.
In accordance with an embodiment of this invention, there are provided three horizontally mounted current limiting fuses (12, 14, 16). These fuses include striker pins each. These striker pins are typically firing pins which provide axial slider movement upon 'firing'. Each fuse is connected to a single phase of a power supply line. Therefore, three fuses meet the requirements of a three-phase power supply.
In accordance with another embodiment of this invention, there are provided three sliding contacts (22, 24, 26) which are coupled to the three striker pins, correspondingly. Each sliding contact is connected to a corresponding striker pin,

thereby representing one phase each of the three-phase power supply line. Any of the striker pins can 'strike' or 'fire' or 'activate' when there occurs any type of winding fault; be it by lightning strike or any other force of nature or short-circuits or overloads or the like faults. The action of 'strike' or 'fire' or 'activate' includes the action of axially movement of corresponding striker pin(s) resulting in corresponding axial movement of all three coupled sliding contacts. The set of sliding contacts is mounted in a staggered motion of typically 1 mm or less, to reduce the force needed to cut the wires. Each sliding contact is a sliding blade. Each sliding contact is a sliding ceramic blade. Each sliding contact is a blade with a V-shaped operative front groove with blades etched in the internal arms of the V-groove. The sliding contacts are coupled contacts such that each of the three contacts is simultaneously activated when a fault on one phase (i.e. at one striker pin fuse) is detected and hence, all three wires are cut individually within milliseconds of each other to reduce the force needed by the blown pin striker fuse.
In accordance with yet another embodiment of this invention, there are provided three stationary contacts (32, 34, 36) which are placed substantially collinear to the three sliding contacts; correspondingly, in a spaced apart manner. The stationary contacts are placed on a housing (30) such that it lends bottom support to the stationary contacts and keeps the operative edge of the stationary contacts free in order to receive a wire. The support is a support made of isolating material. The preferred support is a nylon support. The set of stationary contacts is mounted in a staggered motion of typically 1 mm or less to reduce the force needed to cut the wires. Each stationary contact is a stationary blade. Each stationary contact is a stationary ceramic blade. Each stationary contact is a blade with a V-shaped operative front groove with blades etched in the internal arms of the V-groove.

The V-grooves of each stationary blade faces the V-groove of each sliding blade in a partially overlapped manner in its non-operative state.
High voltage winding wires (42, 44, 46) are placed in between the sliding contacts and the stationary contacts such that a single wire (each phase) is passed through the spaced-apart region between a corresponding sliding contact and a corresponding stationary contact. Typically, the wires are blank or enameled copper or aluminum wires.
In accordance with still another embodiment of this invention, there are provided spring loaded plungers (56 representing third phase - shown in a split open tube 66) housed inside vertical insulation tubes (62, 64, 66) which receive the winding wires. Preferably, the plunger is a brass or copper plunger. The plunger is a tensioned plunger (due to spring represented by reference numeral 60) against the force of gravity. Each vertical insulation wire receives a wire. Hence, each plunger is coupled to a wire. When the wire is cut between the V-grooves of the blades, the plunger works, due to tension and gravity, and draws the lower part of the cut wire away from the upper part of the cut wire within milliseconds of actuation. This reduces the force needed by the blown pin striker fuse.
The wires are preferably soldered or screwed into the spring loaded plunger to separate the wires as quick as possible after being cut to reduce high voltage arcing within a transformer or equipment associated with the disconnector. As part of the disconnector, the spring loaded plungers are housed inside insulation tubes. The bottom of the tubes have a restriction to prevent the plunger from falling out of it after being ejected down by the initial spring force and in turn the weight of the plunger itself.

The disconnector provides a mechanism to disconnect a failed transformer or equipment associated with the disconnector from all three phases of the power supply by any occurring internal fault to prevent huge expense of repair and long periods of time without electricity for customers.
In working state, when fault occurs in any one of the lines, the fuse element detects the fault current, and actuates its associated sliding pin. The V-groove of the sliding contact (blade) moves towards the V-groove of the stationary contact (blade) in an overlapping fashion and, in turn, cuts a corresponding wire running the space between the V-groove of the sliding contact (blade) and the V-groove of the stationary contact (blade). The plunger associated with the wire works towards detaching the components of the cut wire away from each other instantaneously to avoid arcing. The movement of one sliding contact blade causes simultaneous movement in the remaining sliding contact blades and all three phases of wires are eventually (yet instantaneously and almost simultaneously) cut to provide instantaneous disconnection.
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 three-phase disconnector, said disconnector comprising:
a) three horizontally mounted current limiting fuses, each of said fuses individually being connected to one phase of a three-phase power supply line and further comprising three corresponding striker pins adapted to axially move in an operative first direction upon detection of an overcurrent fault;
b) three sliding contacts coupled to said three striker pins, correspondingly, each of said sliding contacts adapted to axially slide in said first direction upon activation of said corresponding striker pin;
c) three stationary contacts placed substantially collinear to said three sliding contacts; correspondingly, in a spaced apart manner and adapted to be partially overlapping in its non-operative state and further adapted to be more than said partially overlapping in its operative state;
d) winding wires being placed in between said sliding contacts and said stationary contacts such that a single wire (one per each phase) is passed through said spaced-apart region between a corresponding sliding contact and a corresponding stationary contact;
e) spring loaded plungers adapted to receive said winding wires, correspondingly; and
f) vertical insulation tubes adapted to receive said spring loaded plungers when they fall down once said winding wires are cut by said contacts.
2. A disconnector as claimed in claim 1, wherein said sliding contacts are mounted
in a staggered motion of a pre-defined distance in order to reduce the force
needed to cut said wires.

3. A disconnector as claimed in claim 1, wherein each sliding contact is a sliding blade.
4. A disconnector as claimed in claim L wherein each sliding contact is a sliding ceramic blade.
5. A disconnector as claimed in claim 1, wherein each sliding contact is a blade with a V-shaped operative front groove with blades etched in the internal arms of the V-groove,
6. A disconnector as claimed in claim 1, wherein each stationary contacts is placed on a housing such that it lends bottom support to the stationary contacts and keeps the operative edge of the stationary contacts free in order to receive a wire.
7. A disconnector as claimed in claim 1, wherein each stationary contacts is placed on a nylon (or similar isolating synthetic material) housing such that it lends bottom support to the stationary contacts and keeps the operative edge of the stationary contacts free in order to receive a wire.
8. A disconnector as claimed in claim 1, wherein said stationary contacts are mounted in a staggered motion of a pre-defined distance in order to reduce the force needed to cut said wires.
9. A disconnector as claimed in claim 1, wherein each stationary contact is a sliding blade.
We claim,
1. An improved three-phase disconnector, said disconnector comprising:
a) three horizontally mounted current limiting fuses, each of said fuses individually being connected to one phase of a three-phase power supply line and further comprising three corresponding striker pins adapted to axially move in an operative first direction upon detection of an overcurrent fault;
b) three sliding contacts coupled to said three striker pins, correspondingly, each of said sliding contacts adapted to axially slide in said first direction upon activation of said corresponding striker pin;
c) three stationary contacts placed substantially collinear to said three sliding contacts; correspondingly, in a spaced apart manner and adapted to be partially overlapping in its non-operative state and further adapted to be more than said partially overlapping in its operative state;
d) winding wires being placed in between said sliding contacts and said stationary contacts such that a single wire (one per each phase) is passed through said spaced-apart region between a corresponding sliding contact and a corresponding stationary contact;
e) spring loaded plungers adapted to receive said winding wires, correspondingly; and
f) vertical insulation tubes adapted to receive said spring loaded plungers when they fall down once said winding wires are cut by said contacts.
2. A disconnector as claimed in claim 1, wherein said sliding contacts are mounted
in a staggered motion of a pre-defined distance in order to reduce the force
needed to cut said wires.

3. A disconnector as claimed in claim 1, wherein each sliding contact is a sliding blade.
4. A disconnector as claimed in claim 1, wherein each sliding contact is a sliding
ceramic blade.
5. A disconnector as claimed in claim 1, wherein each sliding contact is a blade with a V-shaped operative front groove with blades etched in the internal arms of the V-groove.
6. A disconnector as claimed in claim 1, wherein each stationary contacts is placed on a housing such that it lends bottom support to the stationary contacts and keeps the operative edge of the stationary contacts free in order to receive a wire.
7. A disconnector as claimed in claim 1, wherein each stationary contacts is placed on a nylon (or similar isolating synthetic material) housing such that it lends bottom support to the stationary contacts and keeps the operative edge of the stationary contacts free in order to receive a wire.
8. A disconnector as claimed in claim 1, wherein said stationary contacts are mounted in a staggered motion of a pre-defined distance in order to reduce the force needed to cut said wires.
9. A disconnector as claimed in claim 1, wherein each stationary contact is a sliding blade.

10.A disconnector as claimed in claim 1, wherein each stationary contact is a sliding ceramic blade.
1 l.A disconnector as claimed in claim 1, wherein each stationary contact is a blade with a V-shaped operative front groove with blades etched in the internal arms of the V-groove.
12.A disconnector as claimed in claim 1, wherein said sliding contacts are coupled contacts such that each contact is simultaneously activated when a fault on one phase (i.e. at one striker pin fuse) is detected and hence, wire is cut individually within milliseconds of each other to reduce the force needed by the blown pin striker fuse.
13.A disconnector as claimed in claim 1, wherein said wires are blank or enameled copper or aluminum wires.
14.A disconnector as claimed in claim 1, wherein said spring loaded plungers are housed inside vertical insulation tubes which receive said winding wires.
15.A disconnector as claimed in claim 1, wherein said spring loaded plungers are brass or copper plungers.
16.A disconnector as claimed in claim 1, wherein said wires are soldered or screwed into said spring loaded plunger, correspondingly.