FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - AN IMPROVED SWITCHGEAR ARRANGEMENT
WITH LESS WATT-LOSS
2. Applicant(s)
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company.
(c) ADDRESS : L&T House, Ballard Estate, Mumbai 400 001, State of
Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE NVENTION
The present invention relates to an electromagnetic shielding which is used in switchgears. More particularly, the invention is concerned about an improved switchgear arrangement with less watt-loss for making the system more energy efficient.
BACKGROUND OF THE INVENTION
An air circuit breaker is used for transmission, making and interrupting large value of three phase current for safe operation of power systems in case of surges, or short circuit symmetric/asymmetric faults. It has three poles excluding neutral, though neutral can be added if need be. Three of its poles are used for carrying three phase currents which have a phase shift of ideally 120°. Even though the current path of breaker has been very efficient in terms of prevention of losses, losses do creep in due to circulating eddy currents in AC transmission, arising due to two factors:
1)Skin effect
2) Proximity effect
These reduce the effective cross section area of the current carrying path through which the current flows, thus increasing the ac resistance, ultimately increasing the total watt loss.
Non-patent literatures such as Cahier technique no. 83 , first issue, January 1983 discloses an extra losses caused in high current conductors by skin and proximity effects and IEEE transactions on magnetics, vol. 36, no. 2, march 2000 discloses One-Sided Fluxes in Planar, Cylindrical, and Spherical Magnetized Structures.
US 2008074223 (Al) discloses a reinforced permanent magnet array includes a plurality of permanent magnets with each magnet being unnaturally aligned with an adjacent magnet and at least one member at least partially embedded in the magnets for resisting a natural tendency of individual magnets to repulse, twist, and separate from one another.

Thus, there is a need to overcome the problems of the prior art. Therefore, present inventors have developed an improved switchgear arrangement with less watt-loss. It would provide an electromagnetic shielding between the poles of an ACB, preventing the alternating flux lines (generated due to alternating magnetic tleid)of one phase to bypass it and cut through other poles, which are carrying current in different phases. As a result of this, alternating magnetic field of one pole is not able to interact with other pole's magnetic field thus reducing the intensity of induced circulating eddy currents, leading to lesser watt loss in AC transmission.
OBJECTS OF THE INVENTION
An object of the present invention is to overcome the problems/disadvantages of the prior art.
Another object of the present invention is to provide an improved switchgear arrangement with less watt-loss.
These and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an improved switchgear
arrangement having less watt-loss, said arrangement comprising:
plurality of electromagnets being operatively connected with each other,
wherein each of said electromagnets being placed one top on the other in a manner that two
consecutive electromagnets of said plurality of magnets comprising current axes substantially
perpendicular to each other and
wherein at least last two electromagnets in the sequence of said electromagnets having less
number of turns than the remaining electromagnets so as to provide lesser watt loss in
transmission.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided an improved switchgear arrangement with less watt-loss. The present invention is a set of arrangement of electromagnets, which can be solenoids or copper enameled wires of a particular gauge, wound around an insulator, where

all the electromagnets are connected in series. The set is made up of five electromagnets (one on top of other) such that the current axis of one electromagnet is perpendicular to it immediate next electromagnet (the set can be made up of electromagnets where the total number of electromagnets could be multiples of five) with the last two of them having lesser number of turns comparatively, which helps in producing unidirectional magnetic field on only one side of the arrangement for one half cycle (say positive half cycle) of AC current at 50 Hz (frequency can vary), with the magnetic field strength of the first three magnets being predominant. Also since it works on AC current, during the negative half cycle it again produces unidirectional magnetic field but in the opposite direction to that of the magnetic field which it produced during the first half cycle (positive cycle). Now the arrangement of the electromagnets in series is such that during positive as well as negative half cycle, the magnetic field generated by the electromagnet is opposite to that of the magnetic field generated by the current carrying poles. For example, if the field of the poles is clockwise in one half cycle, then the field generated by the coils would be counter clockwise. Thus it caters to both cycles of the ac current. The greatest benefit of this arrangement is that it changes the magnetic field it generates as per the change in magnitude of ac current as its source is the secondary of Current Transformer, which is already present in the Air Circuit Breaker. Now the Current Transformer of each phase in the present application is used to power up the protection and control unit. The current output required to power up the P&C unit is as less as 0.75 Amperes. In the breaker each phase has its own Current Transformer i.e there would be three different current transformers for three different phases. By changing the number of turns of the secondary winding (reducing it) of the current transformer the output current is varied from 0.75A to 3A, where the additional current would be utilized for powering up the electromagnet.
The magnetic field produced by the arrangement to counter the magnetic field of the current carrying parts of ACB would be directly proportional to the number of turns and the current it draws from the source i.e H = NI/L. Such an arrangement of the coils not only helps in reducing the proximity effect but also the skin effect by affecting the distribution of current density in the pole, which happens due to change in magnetic field around the pole. Thus, it can be said that the extra watt loss occurring in Air Circuit Breakers due to AC current is taken care of by this arrangement leading to a more energy efficient system. Also by reducing the hot spots due to AC current, life of the copper terminals is extended.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Other features as well as the advantages of the invention will be clear from the following
description.
In the appended drawings:
Figure 1 illustrates an entire Air Circuit Breaker assembly.
Figure 2 illustrates an isometric view of the breaker.
Figure 3 illustrates a back view of the entire breaker.
Figure 4 illustrates a set of electromagnets.
Figure 5 illustrates a position of top terminal electromagnets.
Figure 6 illustrates an enlarged view of the coil arrangement.
Figures 7 and 8 illustrate an arrangement of electromagnets.
Figures 9 and 10 illustrate an arrangement of electromagnets (negative cycle of AC current).
Figures 11 and 12 illustrate an arrangement of electromagnets which is used for the shielding
of Y phase from that of R phase.
Figures 13 and 14 illustrate a unidirectional magnetic field lines.
Figure 15 illustrates an arrangement of the electromagnet coils in the breaker.
Figure 16 illustrates a back side view of the Air Circuit breaker.
Figure 17 illustrates an enlarged view of electromagnetic coil.
Figure 18 illustrates an entire current path of the breaker.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the arrangement has been discussed below to describe the way the arrangement operates. However, such description should not be considered as any limitation of scope of the present unit. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.

According to a preferred embodiment of the invention, there is provided an improved switchgear arrangement with less watt-loss. Figure 1 shows the entire Air Circuit Breaker assembly. (1) shows the facia of the breaker which is the front covering. (2) shows the entire mechanism responsible for the opening and closing of the breaker. (3) is the front housing (housing of the breaker is in two parts , front and rear) of the breaker and (4) is the entire rear housing along with the entire current carrying path.
Figure 2 shows the isometric view of the breaker from the back with (5) depicting a single phase B of the breaker. It consists of two terminals, upper and lower.
Figure 3 shows the back view of the entire breaker with all the three phases marked distinctively, (5) being the B phase, (6) the Y phase and (7) the R phase. Each of these phases consists of two terminals, upper and lower collectively called as poles.
Figure 4 shows the set of electromagnets need power to produce the desired amount of magnetic field. This comes from the current transformer which in existing product is being used for powering up the protection and control unit. (8) shows Rogowski Coil used for detection of current in a phase, and this is being used in all the three phases. (9) shows the current transformer, (10) being the iron core and (11) showing the wires to be used for powering up the electromagnets. Separate wires (apart from S1 and S2) can be taken out of the CT for powering up the protection and control unit. In the existing product only one CT is used per phase and that too at the bottom terminal. In the new design there would be two of them per phase, one at the top terminal and the other at the bottom terminal. The bottom terminal CT would be powering up electromagnets next to it as well as P&C unit. The top terminal CT would be used for powering up the electromagnet adjacent to it. However the power drawn from the source would be very less as each CT needs to draw roughly 2~2.5 Ampere based on its number of secondary turns. The need for two CTs can be justified by saying that it is required for producing magnetic field in opposite directions with respect to the magnetic field of the upper and lower terminals because taking the first half cycle into consideration, if we assume that current is entering through top terminal then it is leaving through bottom terminal in the same half cycle. Thus if we refer to (5) of figure 3 we can visualize that if current is going into the plane in top terminal of say B phase then the magnetic field produced would be in clockwise direction going by the right hand thumb rule. However if the current is coming out of the lower terminal of B phase then the field produced

would be in anticlockwise direction. Now the CT is generally put around the bottom terminal with its P2 surface facing outwards (FIG 4). But if it is put other way round, than S1 and S2 get reversed (i.e polarity for one half cycle is reversed) as a result of which magnetic field direction produced by that of the electromagnet receiving that supply gets reversed for that particular half cycle. Therefore, the bottom-line is, at any point of time in a single phase, the top terminal CT and bottom terminal CT should be around the terminals in such a way that one should have face P1 outwards and the other should have face P2 outwards.
Figure 5 depicts the position of top terminal electromagnets in the rearhousing to provide basic shielding between the poles of an ACB (bottom terminal electromagnets cannot be seen in this figure). (12) is the female part of the (14) pole cage assembly which is actually connected to the mechanism shaft and changes its position when breaker is switched on and off. (13) is the rear housing on which the entire setup is mounted. (15) is the are runner of the breaker.
Figure 6 shows the enlarged view of the coil arrangement in between the poles/phases. This is connected with the top terminal CT of its phase.
Figures 7 and 8 depict an arrangement of electromagnets,where the magnetic alignment has been decided based on the right hand thumb rule. In this case the copper enameled wire or wire made out of any other conducting metal is wound around the core of an insulator(can be air core as well) and current is passed through it, thus creating a magnetic field of its own. Total number of turns and amount of current to be passed can be decided by the user, depending on the magnetic field required. (22) shows the supply as current source (in our case it is a Current Transformer), however any current pumping device can be used for this arrangement to work properly. The arrows actually are wires of the same thickness connected as shown in the diagram for better clarity, with the arrow heads depicting the direction of the current for one half cycle. This arrangement shows the flow' of current in positive half cycle of the AC current fed through the CT and (22a) shows the magnetic field lines produced if (22) is looked at from right hand side with the other side going completely flux less. This arrangement of coils is to be used either next to the top or bottom terminal of the B phase. This arrangement leads to better skin effect reduction in B Phase. Note, that the number of windings in the bottom two electromagnets is lesser than that of the top three.

Figures 9 and 10 show the same arrangement as above except for the fact that in this case the current flows in the reverse direction (negative cycle of AC current), producing the flux lines as shown in (23a). Thus it can be seen that this special and unique arrangement caters to both cycles of AC current. The working can be verified by the usage of right hand thumb rule. Note that the lower two electromagnets have lesser number of windings as compared to the top three in all of these setups. Again this set has to be used only for the shielding of Y phase from B phase. This arrangement however leads to better skin effect reduction in B phase.
Figures 11 and 12 show the arrangement which is slightly different than that of the previous two and this is supposed to be used for the shielding of Y phase (top or bottom terminal based on CT arrangement) from that of R phase. Again the number of turns in the last two electromagnets are lesser than that of the first three. This arrangement produces unidirectional magnetic field lines (24a) only on one side of the plane (this time the other side) with the second side devoid of any field lines. This arrangement however leads to better skin effect reduction in R phase.
Figures 13 and 14 depict unidirectional magnetic field lines, (25a) this time counterclockwise with the same arrangement as above but during the negative half cycle of AC current. This again has to be used for the shielding of Y phase from that of R phase. However this arrangement leads to better skin effect reduction in R phase. Again the number of turns in the last two electromagnets got to be less than that of the first three.
Figure 15 shows the arrangement of the electromagnet coils in the breaker along with the current carrying parts. This is how the new invention is supposed to be used in the actual Air Circuit Breaker. (9) shows the CT with its P2 side outwards. Six such CTs are to be used with two CTs for each phase, with different face pointing outwards per phase. (14) depicts the entire pole cage assembly with (15) being the arc chute. As mentioned above in Figures 7&8, Figures 9&10, Figures 11&12 and Figures 13&14 , (22) is being used next to B phase top terminal, (23) is used next to B phase bottom terminal, (24) is used next to R phase top terminal, and (25) is used next to R phase bottom terminal. Though (26) represents the bottom terminal of B phase, the bottom terminals in all the phases are very much the same. Similarly (27) is the top terminal of the R phase, but then again top terminals of all these phases are same. (28) is the moving contact button and (29) the arcing contacts of the Air Circuit Breaker.

Figure 16 shows the back side view of the Air Circuit breaker depicting the poles of all the three phases and the arrangement of the electromagnetic coils next to them.
Figure 17 depicts the enlarged view of electromagnetic coil (25) being used adjacent to the bottom terminal of R phase. In this Figure a black dot is placed at the centre of the terminal showing the current is coming out of the plane (assume negative half cycle) and the magnetic field produced by it. Now (25) depicts the magnetic field lines produced by it which is being fed by the bottom terminal CT of R phase. As one can see, field of the terminal in clockwise direction is opposed by the anticlockwise directional field of the electromagnet arrangement.
Figure 18 shows the entire current path of the breaker. (14) shows the entire pole cage assembly in open condition. When closed arrow marks show the way current flows in one half of the AC cycle. (30) is the hinge point about which it (14) rotates in forward direction making a contact with the top terminal. However it is connected at the bottom terminal through either crimping or welding.
ADVANTAGES OF THE INVENTION
1. Less watt loss in AC transmission
2. Life of the copper terminals is extended

We Claim
1. An improved switchgear arrangement having less watt-loss, said arrangement
comprising:
plurality of electromagnets being operatively connected with each other,
wherein each of said electromagnets being placed one top on the other in a manner
that two consecutive electromagnets of said plurality of magnets comprising current
axes substantially perpendicular to each other and
wherein at least last two electromagnets in the sequence of said electromagnets having
less number of turns than the remaining electromagnets so as to provide lesser watt
loss in transmission.
2. Arrangement as claimed in claim 1, wherein said electromagnets being connected in series.
3. Arrangement as claimed in claim 1 comprising five or more electromagnets in multiples of five.
4. Arrangement as claimed in claim 1, wherein said plurality of electromagnets selectively comprising solenoids or copper enameled wires.
5. Arrangement as claimed in claim 1, further comprising rogowski coil means adapted to detect current in a phase.
6. Arrangement as claimed in claim 1, further comprising at least two current transformer means adapted for powering up the electromagnets.
7. Arrangement as claimed in claim 6, wherein said current transformer means being an iron core means and plurality of wire means.
8. An improved switchgear arrangement with less watt-loss as herein substantially described and illustrated with the accompanying drawings.