FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - ELECTRICAL OPERATING MECHANISM FOR
MOLDED CASE CIRCUIT BREAKER USING TWO PLUNGERS
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 invention
The present Invention relates to an improved electrical operating mechanism (EOM) for switchgear applications. More particularly, the invention relates to an improved electrical operating mechanism comprising unique plunger assemblies for enhancing the performance of long stroke solenoid by reducing flux leakage to minimum thereby improving the efficiency of the operating mechanism.
Background and the Prior art
A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.
In the present time technologies Motor operator are used for the Remote Operation and merely very few are using Solenoid Operator. The size of the Electrical Operating Mechanism (EOM) is large due to coil accommodations. The Motor operator is preferred in current technologies since the power required to operate the Motor Operator EOM is less compared with Solenoid Operator EOM.
US4620171 discloses a molded case circuit breaker includes a manually resettable under voltage trip mechanism for initiating a trip operation of the circuit breaker upon an under voltage condition. The under voltage trip mechanism includes a solenoid having a fixed electrical coil surrounding a pair of separable movable ferromagnetic plungers. Disposed between and captured by the two plungers is a compression spring for physically separating the two plungers upon the occurrence of an under voltage condition. Upon such an under voltage condition, one of the plungers is positioned to engage and rotate a trip lever for initiating a trip operation of the circuit breaker. The other plunger is secured to an elongated manually depressible reset button that extends through the molded case of the circuit breaker. After a trip

operation, the reset button can be depressed to re-establish physical engagement between the first and second plungers, enabling the circuit breaker to be reset.
US5341191 discloses a molded case circuit breaker having current limiting capabilities optimized for relatively smaller frame sizes. More specifically, one aspect of the invention relates to a two-piece carrier assembly for carrying the main and arcing contact arms which allows the main and arcing contacts to be blown open during short circuit conditions. The two-piece carrier assembly includes an inner carrier and an outer carrier pivotally connected together. The contact arms are carried by the inner carrier. When sufficient magnetic repulsion forces are exerted on the contacts due to a short circuit condition, the inner carrier pivots relative to the outer carrier to allow the contact arms to blow open. In order to control the amount of force required for blow open, a compression spring loaded cam assembly is provided. Another important aspect of the invention relates to a contact spring housing which relocates the contact springs away from the separable contacts to protect the springs from damage, for example, from heat due to contact separation. In order to improve the interruption time of the circuit breaker for relatively large overcurrents, such as a short circuit, a reverse current loop is provided which generates sufficient magnetic repulsion forces to blow open the separable contacts in a relatively short period of time. Within the restraints of the physical dimension of a relatively smaller breaker frame size, additional features have also been incorporated. More specifically, an improved rating plug assembly is provided with a one-piece plunger, relatively easier to manufacture than known designs which utilize two-piece plungers. Another aspect of the invention relates to an auxiliary cam plate for controlling the motion of the crossbar at the remote end in a four pole circuit breaker. The cam plate compensates for bending of the crossbar to improve the contact force in the remote pole. Lastly, a molded interphase barrier forms a gas barrier within the circuit breaker and maintains its position during assembly relatively better than known interphase barriers.
US4097831 teaches an accessory apparatus package for electric circuit breakers includes a pivotal lever for latching a spring powered trip slide in a reset position. Either of two shunt trip solenoids acts on this lever to unlatch the slide, which springs to an actuated position, initiating tripping of the breaker. A UVR solenoid can also act

on this lever to unlatch the slide. A powerful reset spring, controlled by the breaker operating mechanism, discharges as the breaker trips to return the slide to its reset position and, in the process, causes the lever and the solenoid plungers to be reset. All parts are operatively mounted by a common support affixed to the breaker.
The main drawbacks of the current Technology are the high power (VA) consumption, bigger coil size and long stroke. In case it consumes high power then it requires separate source for the operation. For the long stroke operation the leakage flux is higher and hence the operating Nl gets increased which results in the increase of the size of the coil.
In the case of Long Stroke Solenoid leakage flux is higher and hence it requires more amount of power (VA) for the operation. The Present invention relates to reduce leakage flux and improve the performance of solenoid by two Plunger assemblies.
The present inventors have found that an electrical operating mechanism designed with unique plunger assemblies is capable of enhancing performance of long stroke solenoid by reducing flux leakage to minimum which improves the efficiency of the operating mechanism.
Objects of the invention
The main object of the present invention is to overcome the problem of the prior art.
Another object of the present invention is to provide an improved electrical operating mechanism in long stroke operation using two plunger assembly.
Another object of the present invention is to reduce leakage flux to minimum and hence the force produced by solenoid gets improved.
Yet another object of the present invention is to reduce final force of the solenoid which keeps the MCCB mechanism and its operation unaffected.
Another object of the present invention is to reduce coil size of the solenoid as a result of which overall size of EOM get reduced.
Further object of the present invention is to reduce the power requirement of the solenoid.

The other object of the present invention is to reduce the initial force required from solenoid due to stored energy in charged spring.
Summary of the invention
An improved electrical operating mechanism for use in moulded case circuit.breaker for enhancing the performance of long stroke solenoid by reducing flux leakage to minimum thereby improving the efficiency of the operating mechanism, said mechanism comprising :
housing; plural core members in said housing which includes ON core member and OFF core member; plural solenoid core means; movable plunger assembly operatively located between said core members, said plunger assembly comprising center plunger means and main plunger means; wherein said main plunger means and center plunger means being collinearly aligned by means of plural guiding means such that center plunger means reduces air-gap in between center limb of core members and said center plunger; said guiding means being further adapted to move said plunger means; plurality of spring means adapted to store energy and is operatively biased with said main plunger means and said solenoid core means; knob means operatively engaged with said plunger means such that movement of the plunger means correspondingly moves the knob means; wherein said spring means provide energy during initial movement of the plunger thereby reducing the energy from the solenoid and wherein at a substantially middle position of travel of said knob means force produce by said spring means tends to zero and the knob is further moved to its final position by means of force produce by the solenoid means.
Detailed description of the invention
Present invention relates to remote operation (ON, OFF, RESET) of the Molded case circuit breaker (MCCB) by using solenoid operation.
Electrical operating mechanism(EOM) consists of two coils wound on coil formers, two E core structures, two plungers(which are mechanically interlock between them), springs(used to store the energy for initial movement).

Normally in E Core structure width of the side core is half that of centre core (cross section area of the side core is halved that of centre core). In the present invention width of the side core is reduced and height of the side core is increased to maintain the halved the area of the centre core. Since width of the core is reduced the space required for wound the coil gets increased. This gives one of additional factors for invention.
In the present invention energising one coil for ON operation and another coil for OFF and RESET operation and hence for a single operation either one of the coil is energised. The moving plunger consists of centre and main plunger. The knob of the MCCB is connected to the main plunger. The plunger assembly is made in such a way that it is mechanically interlocked. Main plunger can move independently or with the help of centre plunger too. The two plungers (both centre and main plunger) are aligned to move in straight path by means non magnetic guiding rods.
The present invention consists of two sets (2*4) of springs; each set consists of four springs. Springs are placed at the corners of main plunger which in turn housed on guiding rods. In two sets of springs one set placed near ON solenoid (called as ON springs) and other set placed near OFF/RESET solenoid(called OFF spring). ON spring helps during starting of ON-OFF operation and vice versa. The springs are used to store energy during completion of stroke and to provide stored energy during initial movement of stroke. The initial movement of the plunger is occurred due to force which provided by solenoid as well as stored energy in the springs; hence initial force or starting force required from the solenoid is getting automatically reduced. The combination of both forces (springs + plunger) is move the knob of MCCB till it reaches middle position.
At the middle position force produced by springs tends to zero and it is rest on guiding rods, from middle position onwards force produced by solenoid is enough to pull the knob of the MCCB as well as charge one spring set (1*4).
In the present invention moving armature consist of two plungers (Main and centre). While energising a solenoid, centre plunger is tends to attract (since air gap between centre limb of E core and centre plunger is less); hence centre plunger try to reduce air-gap. The model is made such a way that when centre plunger starts move it is

gets interlocked with main plunger. As a result main plunger tends to move with a help of centre plunger.
The efficiency of solenoid is reduced mainly due to leakage flux; leakage flux is higher when air-gap is higher .In the present invention two Plunger Assembly reduce leakage flux to minimum by minimising air-gap and hence efficiency is improved.
In Present invention initial force or starting force from the solenoid is less due to charged springs and hence it reduce coil size of solenoid as a result overall size of the EOM is reduced. Due to provision of the two Plunger the working air-gap is reduced to halved and hence the Amp-Turns required for solenoid is reduced which reduces the EOM overall size and power (VA) requirement.
In the normal Solenoid operation Residual flux is present after de-energising the coil, these plays major role when energising another coil and hence starting force of Plunger gets reduced. In order to avoid the above problem charged springs are used to overcome Residual Magnetism.
In the normal Solenoid operation force produced by the solenoid at the end of stroke is very high but in the present invention due to provision of springs very high final force gets limited, hence the solenoid operation does not affects the' MCCB mechanism and its operation.
In the present invention total stroke is divided into two, first halve by centre plunger and other by main plunger. After completion of first halve of stroke, main plunger starts to move. Main plunger uses parallel path reluctance principle. The above principle reduces magnetic circuit reluctance to halve as a result force gets doubled; hence this force is sufficient to move the MCCB knob as well as charge the springs.
Brief description of the accompanying drawings
Figure 1: Modified E-core structure shows deceased vvidth and increased height of side core
Figure 2: Two plunger assembly
Figure 3: top view of solenoid
Figure 4: OFF-ON operation
Figure 5: complete view of electrical operating mechanism (EOM)

Detailed description of the accompanying drawings
Figure 1 represents modified E-Core Structure which shows the centre limb of E-core (1) and decreased width and increased height of side core (2) which reduce size of the solenoid.
Figure 2 represents two plungers Assembly, main plunger (3) is moving independently as well as with centre plunger (4) too. It also indicates how the EOM is connected with MCCB using MCCB knob connector (5).
Figure 3 represents top view of the solenoid. In fig 3a indicates initial position where 6 is ON solenoid E-Core; 7 denotes ON solenoid coil and 8 denotes ON solenoid coil former, due to centre plunger (4) working air-gap and leakage is reduced to minimum. In fig 3b centre plunger (4) completes its stroke and hence main plunger (3) moves on Parallel path reluctance principle. In fig 3c indicates final position of OFF-ON operation where 9 is the OFF solenoid coil former; 10 is the OFF solenoid coil and 11 denotes OFF solenoid E-core.
Figure 4 represents OFF-ON operation. In fig 4a shows when ON solenoid coil (7) is energized main plunger (3) moves with the help of OFF springs (13), the other components are OFF solenoid E-core (6), EOM enclosure (12); ON spring at free length (14). In fig 4b indicates completion of centre plunger (4) stroke and initiation of main plunger (3) stroke. In fig 4c indicates completion of full stroke and charging of ON springs (18) for reverse operation where 17 is the OFF spring at free length. ON-OFF operation occurs in vice versa.
Figure 5 represents the complete view of EOM and its different components.

We Claim
1. An improved electrical operating mechanism for use in moulded case circuit
breaker for enhancing the performance of long stroke solenoid by reducing
flux leakage to minimum thereby improving the efficiency of the operating
mechanism, said mechanism comprising :
housing;
plural core members in said housing which includes ON core member and OFF core member;
plural solenoid core means;
movable plunger assembly operatively located between said core members, said plunger assembly comprising center plunger means and main plunger means;
wherein said main plunger means and center plunger means being collinearly aligned by means of plural guiding means such that center plunger means reduces air-gap in between center limb of core members and said center plunger; said guiding means being further adapted to move said plunger means;
plurality of spring means adapted to store energy and is operatively biased with said main plunger means and said solenoid core means;
knob means operatively engaged with said plunger means such that movement of the plunger means correspondingly moves the knob means;
wherein said spring means provide energy during initial movement of the plunger thereby reducing the energy from the solenoid and wherein at a substantially middle position of travel of said knob means force produce by said spring means tends to zero and the knob is further moved to its final position by means of force produce by the solenoid means.
2. Electrical operating mechanism (EOM) as claimed in claim 1 wherein said
core member is E-core.

3. Electrical operating mechanism (EOM) as claimed in claim 1 wherein said main plunger and centre plunger are further mechanically interlocked.
4. Electrical operating mechanism (EOM) as claimed in claim 1 wherein said guiding means comprises non-magnetic guiding rods.
5. Electrical operating mechanism (EOM) as claimed in claim 1 wherein plurality of spring means comprises two sets of springs having four springs in each set of spring.
6. Electrical operating mechanism (EOM) as claimed in claim 4 wherein one of the spring set placed near ON solenoid and the other set of spring is placed near OFF/RESET solenoid.
7. Electrical operating mechanism (EOM) as claimed in any preceding claim wherein said main plunger operates under parallel path reluctance principle.
8. Electrical operating mechanism (EOM) as substantially described hereinbefore with reference to accompanying drawings.