Form - 2
THE PATENTS ACT, 1970
COMPLETE SPECIFICATION (SECTION 10)
"Multiphase ac Current Carrying Conductor".
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate,
Mumbai - 400 001,Mharashtra State, India
An Indian company duly registered and incorporated under
Company's Act, 1956.
The following specification particularly describes and ascertains the nature of the invention and the manner in which it is to be performed: -


FIELD OF THE INVENTION
The present invention relates to a multi phase circuit breakers, switch board links and the like adapted to take care of sub-effective use of the circuit breakers/switch boards due to proximity effects at higher ac current flow through such conductors and better heat dissipation thereby avoiding problems of over heating and consequential break down as well as capability of adapting to high electrodynamic forces under short circuit conditions of such circuit breakers/ switchboards.
BACKGROUND ART
Circuit breakers are usually of varying capacities and are selectively used depending upon the operating voltage. Thus circuit breakers for low voltage application (voltage generally upto 1000 V ac) generally find application at operating currents ranging of the order of 7000 A. Such devices are mainly used in three phase configuration.
To handle such large currents, it is known that the main current carrying path of the circuit breaker, generally referred to as a pole, is made up of several parallel conducting paths
For upto 3,000 A or so circuit breakers are generally provided with one pole only. For higher ratings, however, since the pole and the associated assemblies become bulkier, which are difficult, to handle for which some manufacturers make up such poles into two halves
It is, however, found that inspire of such use of multiple parallel conducting paths in circuit breakers when required to handle large AC current the performance of such circuit breakers usually get affected due to unwanted heating of the circuit breaker and consequential accompanying complexities and/or break down of the unit
-The main disadvantage of the conventional circuit breakers provided with a single pole is that during high AC voltage or high AC current performance of the

conductors, the conductors gets over-heatedue to bad heat dissipation thereby leading to consequential breakdown ofthe unit.
Another disadvantage of the circuit breaker using multiple parallel conducting paths is that the AC current carrying poles of the circuit breakers when encountering higher currents in multiple parallel paths give rise to skin and/or proximity effects.
One more disadvantage is that in case of three phase circuit breakers designated as R, Y and B, the Y phase is sandwiched in between R and B having worst heat

The other disadvantage is that under short circuit condition in AC current carrying circuit breakers high electro dynamic forces pull and push the current carrying poles based on the same/opposite and rapidly changing direction of the current, whichagain affect the current carrying capacity as well as the performance of the circuit breaker.
In the conventional circuit breakers there are no interleaving current carrying link connection in the switching means.
OBJECT OF THE INVENTION
It is thus the basic object of the present invention to provide a multiphase circuit breaker which would be adapted to take care of problems of over heating and sub-effective use of the AC current carrying conductors of circuit breakers due to proximity effects at higher ac current flow and also favour better heat dissipation thereby avoiding problems of over heating and consequential break down as well as capability of adapting to high electrodynamic forces under short circuit conditions
Another object of the present invention is to provide multiphase circuit breakers which would have improved capacity by way of even distribution of high load ac

current in the current carrying path and favour reduced resistance (R ac) to current flow and thereby avoid unwanted heating and its related problems.
Another object of the present invention is to provide for a multiple phase circuit breaker which would have the poles of the three phases sequenced such that the heat or the temperature rise due to the difference of heat generation and heat dissipation^ is effectively controlled by a more_ uniform and controlled heat distribution in the current carrying prales of the circuit breaker.
Yet further object is directed to take care of draw backs associated with short circuit conditions in circuit breakers when high electro dynamic forces push and bull the poles based on the same/opposite and rapidly changing the direction of current.
Yet another object of the present invention is directed to provide a modified circuit, breaker housing adapted to dispose the ac. current carrying conductors of the circuit breaker in split configuration such that the problem of proximity effect at higher ac current flow could be avoided favoring better heat dissipation and performance of the circuit breaker as well as its adaptability to high electrodynamic forces under short circuit conditions.
Another object of the present invention is directed to provide for circuit breakers which would accommodate split pole construction and favour advantageous use of such split poles and at the same time maintain a compact and user friendly housing and combination features of the circuit breaker.
Yet another object of the present invention is to provide switch boards which would favour even distribution of ac current in its current carrying path/poles maintaining the switching device cool and improving upon the capacity of the switch board.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is a provided a multiphase circuit breaker comprising:

current carrying, poles of each phase split into at least two parallel parts to constitute plurality of split parallel paths of the poles, said split paths arranged such that the split paths of the same phase are kept distanced from one another by an intermediate split path selected from the split paths of the other phases.
In accordance with a preferred aspect the multiphase circuit breaker is of a three phase configuration comprising:
current carrying poles of each phase split into atleast two parts to constitute
plurality of split parallel paths of the poles, said split paths arranged such that the split paths of one phase is kept distanced from one another by intermediate split paths selected from the split paths of the other two phases.
In accordance with another aspect of the present invention there is provided a
multiphase circuit breakers comprising:
- current carrying poles of each phase including the .neutral split into at least two parts to constitute plurality of split parallel paths of the poles, said split paths arranged such that the split paths of one phase is kept distanced from one another by intermediate split path selected from the split paths of the otherj phases.
In the above circuit breaker of the invention the parallel poles of the respective phases are not placed adjacent to one another as is conventionally done and instead are interleaved by an intermediate split pole of another phase. Importantly, such an arrangement of two different split poles of different phases adjacent one another avoid the problems of skin effect and/or proximity effect in use of similar poles of the same phase placed adjacent one another thereby take care of problems of over heating consequential and consequential breakdown as well as the adaptability to tackle high electrodynamics forces under short circuit conditions.

In accordance with a preferred aspect of the invention the current carrying poles of each phase are split into two parts to define two parallel poles of each phase which are interleaved by a split path/pole of the other of the two phases.
In accordance with yet further aspect of the present invention the multiphase circuit breaker is provided with selective current carrying path wherein each of the poles of the various phases including neutral are split into two parallel parts and the two parts are arranged such that the adjacently disposed split poles are of different phases.
In accordance with yet further preferred aspect of the present invention there is provided a multiphase circuit breaker comprising a three phase circuit breaker having three corresponding poles (R, Y and B), each said pole (R/Y/B) split into two parts (R1, R2/Y1, Y2/B1, B2) and wherein the poles are disposed interleaved such that the adjacently disposed split poles are of different phases (R1-Y1-B1-R2-Y2-B2).
In accordance with yet further preferred aspect of the present invention there is provided a multiphase circuit breaker comprising multi phases including the neutral having corresponding poles (N, R, Y and B), each said pole (N/R/Y/B) split into two parts (N1, N2 /R1,R2/Y1,Y2/ and B1.B2) and wherein the poles are disposed interleaved such that the adjacently disposed split poles are of different phases (N1-R1-Y1-B1 - N2 - R2 - Y2 - B2).
According to another aspect of the present invention there is provided a circuit breaker comprising:
a two part housing each said part adapted to accommodate separately one of the current carrying split poles of the respective phases and arranged such that the split paths of the same phase are kept distanced from one another by an intermediate split path selected from the split paths of the other phases.; said parts further adapted to be releasably secured such that the pitch distance between the poles is uniformed and together define a compact width of the circuit breaker.

In accordance with a preferred aspect the above circuit breaker and in particulate a two part housing and its provision for the split poles are such that the distance between two adjacent pole is maintained in the range of 30-40 mm.
Also, in accordance with yet further preferred aspect the effective separation between the phases is achieved by provision of glass filled unsaturated polyester material in the form of thin walls to achieve the required strong partitioning between phases.
In the above circuit breaker configuration adapted to accommodate the split poles, to take care of the proximity effects the current transformer is also selectively provided in two halves. The current of the respective halves are added and fed to the protection device. This favours for accurate transformer development.
In accordance with yet further aspect of the present invention there is provided a switchboard comprising multiphase operating system comprising:
current carrying poles of each phase including neutral split into atleast two parts to constitute plurality of split parallel paths of the poles, said split paths arranged such that the split paths of a phase are kept distanced from one another by intermediate split path selected from the split paths of the other phases.
The above disclosed arrangement/sequencing of the current carrying path in multiphase circuit breakers/switch board makes effective use of distinction between ac resistance (called R ac) and dc resistance (called R dc) and bringing the ratio R ac / R dc closer to unity.
The R dc is the resistance of the current carrying path when carrying dc current while R ac is the corresponding value while carrying ac current. When ac current is handled, skin effect and proximity effect causes flow of current only along distant peripheries of the conductor. This amounts to sub- effective use of the cross section of the conductor. Since effective resistance is inversely proportional to the cross section it results in higher effective ac resistance or R ac.

In the present invention the use of two poles of any phase are not adjacent each other but interleaved with a parallel pole of the other phase. Such an arrangement avoids the skin effect and/or proximity effect and provides for a more uniform distribution of the ac current flowing through the conductor in the circuit breaker.
While the R dc value remains the same in any situation, the R ac value drops down resulting in ratio coming closer to unity. The heat loses that are governed by l2R ac fall, leading to increased capacity of the circuit breaker.
Also, it is found that in conventional sequencing the Y phase,, which is completely sandwiched in between the R and B has worse dissipation condition. Since temperature rise is the arithmetic difference of heat generated and heats dissipated Y phase dictates the ratings of the circuit breakers even though R and B phase per cooler. The intervening disposition provides for heat dissipation condition, which are more uniform and balanced.
Under short circuit condition, high electro dynamic forces push and pull the poles based on the same/opposite and rapidly changing direction of current. Interleaving reduces the intensity of the forces due to sub-division as well as distribution.
Importantly, in case of the use of such interleaving arrangement of the split poles
of the current carrying means can be advantageously used especially where long
lengths of links are required to be connected. The present system facilitates
interleaving to be extended to this link connections, the effective ac resistance of
the links also reduces and the entire switch board runs cooler or less material /
would be required to carry the same current. '
BRIEF DESCRIPTION OF ACCOMPANYING FIGURES:
The details of the invention, its objects and advantages are explained hereunder in greater detail in relation to non-limiting exemplary illustration as per the accompanying figures wherein:-

Figure 1 shows the current distribution condition ;
Figure 2 shows the new arrangement of the poles of the circuit breaker in accordance with the present invention;
Figure 3 shows the new arrangement of poles/current carrying means in switchboards in accordance with the invention; Figure 3a shows the provision of two parts of the modular housing of the circuit breaker according to the invention to accommodate multiple split poles; and Figure 3b illustrates the disposition of the poles interleaved after the two parts of
the modular housing are secured to one another to define a compact housing of

the present circuit breaker.
As shown in Figure 1, the distribution of current in the current carrying path under various conditions and disposition of such path is illustrated in figure 1. The dots in the conductors (1, 2, 3, 4, 5 and 6) represent the current distribution. Conductor (1) shows distribution of direct current. Conductor (2) shows the distribution of current of alternating current when it is not in the vicinity of any other current carrying conductor wherein skin effect is demonstrated. Conductors (3 and 4) show the alternating current distribution when current flows in the same direction while the same is shown by conductors (5 and 6) when current flows in opposite direction. These two cases show the cases of proximity cases over and above the skin effect in ac distribution. As would be clearly apparent from the above, there is significant reduction in the utilized or effective cross section of the conductor in case of direct current carrying conductors.
Reference is now invited in accompanying figure 2 which illustrates in sectional view a circuit breaker in accordance with the present invention wherein the distribution of the poles are as proposed under the present invention.
As is clearly apparent from the said figure 2, instead of the conventional disposition of the three phases (R, Y and B) in the form of parallel split poles disposed as R1 and R2, Y1 and Y2 & B1 and B2, in accordance with the invention the poles are arranged as R1-Y1-B1-R2-Y2-B2. The above selective disposition/arrangement or sequencing of the poles as interleaved lead to balancing of proximity effect this results into reduced R ac value for all the

phases while R dc values remain uneffected. Lower R ac / R dc ratio result into lower heat loses or cooler running or higher possible continuous current rating.
As fault currents of the order of 50000 A and above, conductors repel or attract each other depending on the direction of current with high force as per the/ equation F a lp2 / S
Where F - force between conductors
lp = Peak value of current
S = Distance between conductors In the above disposition of current carrying conductors the theoretical current per pole is h.alved, at the same time the effective distance between phases is increased This results in significant reduction in electro dynamic forces and enable the circuit breaker to handle higher short circuit current as well.
Reference is now invited in figure 3 wherein interleaved circuit breaker design facilitates interleaving to be extended to the switchboard as well without the need for complex joint. Since the length of the current carrying path in the form these links run into several meters the net benefit in terms of reduction in R ac of any system can be still larger making entire system to run cooler.
Reference is now invited to accompanying figures 3a and 3b which illustrate the (selective modifications in the housing of the circuit breaker of the invention to achieve provision of the interleaving between the split poles of a multiphase circuit breaker.
As shown in figure 3a, the modular construction of the housing in accordance with the invention has been achieved in such a way that in one hand the advantages of split poles have been provided for and on the other hand the circuit breaker housing is maintained compact and of desired width. As clearly shown in said figure, for the purpose, the housing is divided into two parts (C1 & C2). Each said part is provided with sections to accommodate the split poles preferably such that to accommodate separately one of the current carrying split poles of the respective phases and arrange such that the split paths of the same

phase are kept distanced from one another by an intermediate split path selected from the split path of the other phases. The arrangement of such split poles is clearly apparent in the combined housing illustrated in figure 3b wherein the poles are shown arranged as B2-Y2-R2-B1-Y1-R1.
Importantly, therefore, the above construction facilitates a compact housing with simple mould (die) and yet provides for such split multiphase poles of the circuit breakers. The two part housing is further provided with means to facilitate releasable securing of the two parts. For the purpose, an intricate dovetail desigj^ which is supplemented by poles is proposed.
Importantly, the arrangement ensures that the pitch distance (8) between the poles is maintained uniformed. The clearance (7) between the poles is maintained in the order of 30-40 mm. In order to facilitate the interleaving arrangement the clearances (7) are selectively provided in between the split poles which are further effectively separated by use of glass filled unsaturated polyester material in the form of thin walls (9). The current transformer (10) in such an arrangement as also shown is selectively provided in two halves. The current are added and fed to the protection device.
It is thus possible by way of the above invention to provide for simple and cost-effective multiphase circuit breakers adapted to reduce value of ac resistance of the main current carrying parts of the circuit breaker due to nullification/reduction in skin effect and proximity effect and higher effective resistance between current carrying part of respective phases. Such an arrangement would enable providing circuit breaker, which can run without much heating and become capable of higher continuous current. The system also results into reduced electro dynamic forces between phases and consequently make the circuit breaker suitable for higher short circuit current. Importantly, the system of the invention in particular the interleaved current carrying link arrangement can be provided in switch boards with advantageous reduced ac resistance R ac for long linked lengths.

claim
1. A multi-phase circuit breaker for avoiding the problems of over heating and frequent breakdown caused by different current flowing effects in the conducting paths of the poles of different phases, said circuit breaker comprising;
a housing,
a plurality of current carrying path for each phase (R,Y,B,N)
accommodated in said housing;
a plurality of parallel conducting paths split out from the current
carrying path of each phase for carrying fractions of the current
flowing through the conducting paths of the current carrying
path;
a plurality of neutral parallel conducting paths split out of the
neutral (N) phase and placed alternatively between the parallel
conducting paths of the said current carrying path of each of the
phases;
polyesters partitions between the said split parallel conducting
paths of the current carrying poles;
switching means in electrical connection with the said current
carrying poles of each of the phases.
A multi-phase circuit breaker as claimed in claims 1 (tolpwherein the partitioning arrangement comprises of glass filled unsaturated polyester material in the form of thin walls adapted for effective strong partitioning between the split poles of each of the phases.
3. A multi-phase circuit breaker as claimed in claims 1 to 3 wherein the current carrying poles are split into two parts to define two parallel conducting paths of jhe poles for each phases.
\. A multi-phase circuit breaker as claimed in claims 1 and 4 wherein the plurality of split-parallel conducting paths of the poles for each phase are

adapted for reducing the effective resistance of the parallel poles of each phase by increasing distances between the poles of the phases.
A multi-phase circuit breaker as claimed in claim 1 to 4 comprising three phases having three corresponding poles (R, Y and B), each said pole (R/Y/B) split into two parts (R1-R2/Y1-Y2/B1-B2) and wherein the poles are disposed split poles are of different phases (R1-Y1-B1-R2-Y2-B2).
A multi-phase circuit breaker as claimed in claims 1 to 5 wherein the neutral pole comprises of a plurality of spit parallel conducting paths adapted for an arrangement such that the split parallel paths of other phases are maintained at particular distances from one another by an intermediate split paths selected from the split paths of the other phases.
A multi-phase circuit breaker as claimed in claims 1 to 7 wherein the arrangement comprises the corresponding poles (N, R, Y and B), each said pole (N/R/Y/B) split into two parts (N1-N2/R1-R2/Y1-Y2/B1-B2) and the poles are disposed interleaved such that the adjacent disposed split poles are of different phases (N1-R1-Y1-B1-N2-R2-Y2-B2).
A multi-phase circuit breaker as claimed in claims 1 to 7 comprising of an interleaving split pole sequencing adapted to avoid the problems of skin effect and proximity effect reducing the chance of over heating of the conductors increasing the capacity of the circuit breaker.
A multi-phase circuit breaker as claimed in claims 1 to 8 wherein the said housing arrangement comprises of two part housings adapted to accommodate separately atleast one of the current carrying split poles of respective phases such that the split parallel conducting paths of the same phases are kept at uniform pitch distances from one another.

. A multi-phase circuit breaker as claimed in claim 10 wherein the two-part housing has provision for the split-poles such that the distance between two adjacent poles is maintained in the range of 30 to 40 mm.
A multi-phase circuit breaker as claimed in claim 1 wherein the switching means comprises of interleaved current carrying link connection adapted for even distribution of AC current and for reducing the complexities of the parallel conducting path joints and the length of the current carrying paths thereby decreasing the value of ac resistance controlling the temperature of the system at a low value.
. A multi-phase circuit breaker as claimed in claim 1 to 12 wherein the switching means comprises of multi-phase AC current carrying conductor arrangement/sequencing adapted to bring the ratio Rac/Rdc closer to unity.
. A multi-phase circuit breaker comprising parallel current transformers for each phase such that both primary part of current transnrner placed at split paths of respective current carrying poles. Thereby supplying total secondary current for each phase to protection device.

Dated this 29thday of June, 2002


Deepak Mehra Agent for Applicant