DESC:TECHNICAL FIELD

The present invention relates generally to a moulded case circuit breaker (MCCB) and, particularly, to an improved structure that provides the modularity in components and connections of the MCCB.

BACKGROUND

A circuit breaker is a mechanical device capable of making, breaking and carrying normal currents and making and breaking currents under specified abnormal circuit conditions such as that of a short circuit or overload.

Circuit breakers are employed in the electrical system or network for switching and protection of electrical equipments. During adverse conditions like short circuit, the current shoots up to an alarmingly high value; this can pose grave threat to the electrical system, as it can cause damage to the equipments and loads installed downstream in the system. The circuit breaker clears the fault rapidly so as to minimize the damage caused by thermal and mechanical stresses to downstream equipments.

A moulded case circuit breaker is a circuit breaker, wherein the arc quenching and fault clearing process takes place inside housing. Broadly, it consists of contacts system, mechanism, currents sensing unit.

The contact system of the circuit breaker consists of fixed contacts and moving contact. During ON condition, a set of springs provide the contact force to maintain the moving contact in ON condition.Thecurrent conducts from the first fixed contact onto the moving contact and then onto the second fixed contact. The fixed contacts are designed in such a way that the during short circuit conditions, an electromagnetic force develops between the moving contact and fixed contacts. The force results in a clockwise torque on the moving contact. Meanwhile there is an anti clockwise torque provided by the springs acting on the contact. The electromagnetic torque acts against the spring torque and enables moving contact to open up and thus clear the fault.

The moving contact with the spring arrangement is neatly assembled inside a rotating chamber called shaft.Different arrangements of springs and shaft configurations are currently employed for maintaining contact pressure.

Arc chute assemblies, made up of deion plates neatly stacked up together are used for pulling, lengthening and quenching of electric arc during fault interruption. A perforated metal sheet or mesh is used sometimes, so as to de-ionize and cool the hot ionized gases. In some breakers, perforated plastic sheet is used as an alternative.Operating mechanism of the circuit breaker enables manually independent opening and closing of the contact system and does four operations: ON, OFF, Trip and Reset.

The trip unit senses the current flowing through the system, and under pre-specified abnormal conditions gives the command signal for the operating mechanism of the breaker to trip i.e., break the circuit. The trip unit used are generally either thermo-magnetic or electronic (microprocessor based) trip unit. The various termination units/modules cater to the various types of termination like direct link, box clamp, rear, tunnel as per the customer requirements at the end point use.

The prior-art document US 7116194 discloses an electric pole for a low-voltage power circuit breaker. However the cited prior-art has certain limitations as mentioned below:
a) In this prior art, the coupling through the three/ four /multiple poles is done by a separate plastic component called coupler, which have protrusions and depressions like structures on either sides to engage with the shaft assemblies. The couplers, as they are made up of plastic, can get deformed easily when exposed to hot gases molten byproducts in the event of short circuit. So, proper coupling cannot be ensured just by means of plastic couplers.
b) Further, there is no vent like structures. So, there can be hazards of hot ionized gases and particles blown out during short circuit fault clearing process. It can pose threat to service and maintenance personnel in the vicinity.
c) Furthermore, the inter pole packing rivets which pass through the multiple poles are not only in close vicinity of hot ionized gases, but alsoaccessible to the outside environment, in certain regions wherever there is no housing/ cover outside the cassettes.

The prior-art document US 5298874 discloses a modular low voltage multi-pole circuit breaker. However the cited prior-art has certain limitations as mentioned below:
a) In this prior art, the three/ four/ multiple poles are coupled only by means of through pins, which run through all the poles. Also, the through pins are exposed to the hot gases and molten byproducts in the event of short circuit. No plastic couplers are provided. So, there is possibility of arcing hazard through the pins.
b) There is no labyrinth provided anywhere in the cassettes. There is risk of arc hazard between poles.
c) Also, the de-ion plate assembly stack is held by means of only arc chute lining, which can burn in the event of short circuit, thus leading to its collapse.

The prior-art document US 6933814 discloses a molded case, cassette type circuit breaker for a multi-pole electrical distribution circuit includes a number of cassettes equal to the number of poles in the multi-pole electrical distribution circuit and a pin disposed through each cassette.However the cited prior-art has certain limitations as mentioned below:
a) In this prior art, the three/ four/ multiple poles are coupled only by means of through pins, which run through all the poles. Also, the through pins are exposed to the hot gases and molten byproducts in the event of short circuit. No plastic couplers are provided. So, there is possibility of arcing hazard through the pins.
b) The construction is such that the interchangeability of trip unit is difficult and time consuming process.

In the view of above mentioned limitations and drawbacks in the existing circuit breakers, there exists a need for an improved double break low voltage moulded case circuit breaker.

SUMMARY

This summary is provided to an improved double break low voltage moulded case circuit breaker. This summary is not intended to identify essential features of the subject matter nor is it intended for use in determining or limiting the scope of the subject matter.

In one implementation, an over-travel indication, a unique feature of the present invention is disclosed. The over travel arrow marking on the shaft assembly quantifies the over travel given by mechanism module to the contacts in degrees as per marking scheme given on cassettes. This ensures the required contact pressure. Also, the exact over travel loss of shaft through the mechanism, if any, is clearly detected.

In one implementation, a modular pole construction is disclosed.

In one implementation, the circuit breaker as disclosed in the present invention comprises of both the through pins as well as plastic couplers so as to ensure sufficient coupling between the poles.

In one implementation, the circuit breaker as disclosed in the present invention the couplers have labyrinth provided so as to prevent possibility of arc hazard between the poles through the through pins.

In one implementation, the circuit breaker as disclosed in the present invention the construction or the architecture is such that interchangeability between trip units is easy and faster as compared to the other existing circuit breakers.

In one implementation, the modular pole construction disclosed in current invention allows assembling one or multiple poles together to form a single or multi-pole breaker. This standardization simplifies assembly line/process and reduces the assembly cost and time. The pole modules (1) together with other modules, broadly mechanism module (27), chassis module (37), housing (38) forms the basic breaker (57). Now, depending upon whether Thermo-magnetic/electronic release breaker, the release unit/module (39) together with the basic breaker (57) to form full breaker (58).

Accordingly in one implementation, a circuit breaker (57, 58) either single pole or multi-pole comprises of a pole module (1), at least two cassettes (2, 3), arc chute assemblies (4), shaft assembly (9), a mechanism module (27), a chassis module (37), a housing (38), a shaft assembly (9), a release module (39), and various joining means comprises of at least one mechanical spacer (32, 33) is disclosed. The circuit breaker (57, 58) is characterized in that, the mechanical spacer (32, 33) includes a fin-like extension on to one side to prevent at least one inter pole joining screws (55) getting live. A cassette coupler (34) is provided in the breaker on two sides of the pole module (1) used for inter-pole mechanical connection. The chassis module (37) having a rib like features on its vertical walls on a line side, which restricts the translational movement of the mechanism module (27) is provided in the breaker. Housing spacers (35) on either side of the pole module (1) are provided in the breakers.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.

Figure 1 illustratesthe exploded view showing various modules of the breaker are shown, in accordance with an embodiment of the present subject matter.

Figure 2 illustrates the exploded view of a pole moduleis shown, in accordance with an embodiment of the present subject matter.

Figure 3 illustrates the cross sectional view of a pole moduleis shown, in accordance with an embodiment of the present subject matter.

Figure 4 illustrates the arc-chute assembly of the breaker is shown, in accordance with an embodiment of the present subject matter.

Figure 5 illustrates the exploded view of shaft assembly with arrangement of spring pins and springis shown, in accordance with an embodiment of the present subject matter.

Figure 6 illustrates the exploded view of moving contact assemblyis shown, in accordance with an embodiment of the present subject matter.

Figure 7 illustrates the exploded view of shaft end caps with energy divertersis shown, in accordance with an embodiment of the present subject matter.

Figure 8 illustrates the overtravel indication on pole module is shown, in accordance with an embodiment of the present subject matter.

Figure 9 illustrates the mechanism module mounted on a pole module is shown, in accordance with an embodiment of the present subject matter.

Figure 10 illustrates the arrangement of joining means of various modules is shown, in accordance with an embodiment of the present subject matter.

Figure 11 illustrates the exploded view of a mech-contact system is shown, in accordance with an embodiment of the present subject matter.

Figure 12 illustrates the assembly of UV /shunt release, auxiliary contacts and trip alarm circuit in the chassis is shown, in accordance with an embodiment of the present subject matter.

Figure 13 illustrates the exploded view of a basic breaker is shown, in accordance with an embodiment of the present subject matter.

Figure 14 illustrates the exploded view of a micro processor release module is shown, in accordance with an embodiment of the present subject matter.

Figure 15 illustrates an exploded view of assembly of release module to basic breaker is shown, in accordance with an embodiment of the present subject matter.

Figure 16 illustrates an exploded view of a breaker is shown, in accordance with an embodiment of the present subject matter.

Figure 17 illustrates the breaker with direct termination is shown, in accordance with an embodiment of the present subject matter.

Figure 18 illustrates the breaker with box clamp terminationis shown, in accordance with an embodiment of the present subject matter.

Figure 19 illustrates the breaker with rear termination is shown, in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Preferred embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.

The terms and words used in the following description are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

In one implementation, the present invention is related to an improved double break low voltage moulded case circuit breaker.

Depending upon the type of electrical installation, circuit breakers used are either single pole or multi-pole. The modular pole construction in current invention allows assembling one or multiple poles together to form a single or multi-pole breaker. This standardization simplifies assembly line/process and reduces the assembly cost and time.

In one implementation, a circuit breaker (57, 58) either single pole or multi-pole comprises of a pole module (1), at least two cassettes (2, 3), arc chute assemblies (4), shaft assembly (9), a mechanism module (27), a chassis module (37), a housing (38), a shaft assembly (9), a release module (39), and various joining means comprises of at least one mechanical spacer (32, 33) is disclosed. The circuit breaker (57, 58) is characterized in that, the mechanical spacer (32, 33) includes a fin-like extension on to one side to prevent at least one inter pole joining screws (55) getting live. A cassette coupler (34) is provided in the breaker on two sides of the pole module (1) used for inter-pole mechanical connection. The chassis module (37) having a rib like features on its vertical walls on a line side, which restricts the translational movement of the mechanism module (27) is provided in the breaker.Housing spacers (35) on either side of the pole module (1) are provided in the breakers.

In one implementation, the circuit breaker (57, 58) comprises of a fixed contact assemblies (21, 22), a moving contact assemblies (11), at least one spring pin (14); andat least one spring (16, 17).

In one implementation, the pole module (1) comprises of a cassette right (2) and a cassette left (3) for housing contact assemblies (21, 22), wherein said at least two cassettes are made up of thermo-set material.

In one implementation, the rib like features holds mechanism module (27) in place and prevents the mechanism module (27) exerting any kind of pressure on the at least one cassettes (2, 3).

In one implementation, the housing spacer (35) is used to secure housing to a mech-contact system (36) and also to insulate an inter pole packing screw (55) from hot ionized gases escaping out from clearance between shaft assembly (9) and the at least one cassettes (2, 3).

In one implementation, the at least two cassettes (2, 3) have cavities that hold the contacts and the arc chute assemblies (4) in place, wherein the shaft assembly (9) rotates inside the cavity of the cassette (2, 3).

In one implementation, the arc chute assembly (4) comprises of multiple one de-ion plate (5), and at least one plastic component (7, 8), whereinthe de-ion plates (5) are arranged and supported by means of an insulating material, arc-chute lining (6) on either sides, and said at least one plastic component (7, 8) called arc guard right (7) and arc guard left (8) is fixed onto the arc chute assembly (4) by means of snap-fit provided in said at least one plastic component (7, 8).

In one implementation, the mechanism module (27) drives the shaft assembly (9) by means of a drive shaft pins (28, 31) which are inserted on either sides of shaft assembly (9), and a lower links (29) of mechanism module (27), wherein the pins (31) passes through the shaft assemblies (9) of the pole module (1) and serve as a coupling between the mechanism module (27).

In one implementation, the at least one mechanical spacer (32, 33) comprises of a mechanical spacer- right (32) and a mechanical spacer-left (33) assembled on sides of a shaft assembly (9).

In one implementation, the mechanical spacer (32, 33) provides an insulation around drive shaft pins (31), in the space between the pole modules (1), wherein the drive shaft pins (31) come in close proximity with a hot ionized gases escaping through a clearance given between the at least two cassettes (2, 3) and the shaft assembly (9).

In one implementation, the cassette coupler (34) is used to provide mechanical connection between the mech-contact system (36), the chassis module (37), the release module (39) and the housing (38).

In one implementation, the chassis module (37) has integral venting channel that helps in diverting and channelizing the hot ionized gases in right direction and preventing the possibility of a flash over.

In one implementation, the chassis module (37) has finger proofing given for release electrical joining screws (60) for the safety of the operator.

In one implementation, an aux actuator (42) is provided indicating the status of the breaker by actuating auxiliary contacts (65) and assembled to the mech-contact system (36).

In one implementation, an EOM indicator (68) assembled onto a side of the circuit breaker (57, 58) which gives the indication of the breaker status for external accessories. The Aux actuator (42) and EOM indicator (68) are prevented from falling out by the housing (38).

Referring now to figure1 shows the exploded view of the breaker. A pole modules (1) together with other modules, broadly a mechanism module (27), a chassis module (37), a housing (38) forms the basic breaker (57). Now, depending upon whether thermo-magnetic/electronic release breaker, a release unit/module (39) together with a basic breaker (57) forms a full breaker (58).

Referring now to figure 2, shows the exploded view of the pole module (1). The pole module(1) consists of two cassettes; cassette right (2) and cassette left (3), made up of thermo-set material and houses mainly the contacts and arc chute assemblies (4).

Referring now to figure 3 shows the cross sectional view of a pole module. There are cavities in both the cassettes (2) and (3) which hold the contacts and arc chute assemblies (4) in place.

Referring now to figure 4, shows the arc chute assembly. The arc chute assembly (4) consists of two de-ion plates (5) stacked up together. The de-ion plates (5) are arranged and supported by means of an insulating material called an arc-chute lining (6) on either sides. A plastic component called arc deflector or arc guard, namely arc guard right (7) and arc guard left (8) is fixed onto the arc chute assembly (4) by means of snap-fit provided In arc deflectors (7) and (8). The design of arc deflectors (7) and (8) is as shown in figure4. The arc deflectors (7) and (8) have ear-like projections as shown in figure 3 which rests on the grooves provided in the cassettes (2) and (3) as shown in figure 3. The arc deflectors (7) and (8) serve the following advantages as mentioned below:
i. Sophisticated structure of arc deflectors (7) and (8) gives rigidness to the arc-chute assembly (4). It ensures that the de-ion plates(5) are intact in their places, even if arc chute lining (6) burns out due to heavy thermal and mechanical stress associated with short circuits.
ii. The plastic material used for arc deflectors (7) and (8) is also a good ablative. The design of arc deflectors (7) and (8) is in such a way that the ablative material is very much in the zone of arcing. As such, due to ablative action, a low value of let-through energy is ensured.

The arc chute assemblies (4) along with the corresponding arc deflectors (7) and (8) are arranged in the grooves given in the cassette (2) as shown in figure3.

The fixed contact assemblies (21) and (22) are then inserted in the cavity in the cassette right (2) as shown in figure.2.

Referring now to figure 5 shows the semi exploded view of the shaft assembly (9).The shaft configuration carrying the moving contact and spring arrangement in the present invention is a unique compression spring flip-locking based double break contact system.The shaft (10) has two cavities on either side which houses the spring holders (15) and springs (16) and (17).

Referring now to figure 6 shows the moving contact (12) which is enclosed within two similar components called moving contact sheath (13). The moving contact sheath (13) prevents possibility of arc root traversing through the shaft (10).

As shown in figure 5, there are four spring pins (14), two of which are fixed on the shaft (10) and other two which are assembled on moving contact assembly (11), moves as the moving contact (12) rotates. The spring pins (14) support the spring holders (15).There are four sets of concentric compression springs (16) and (17) acting on moving contact (12) as shown in figure 5. Each set consist of two concentric compression springs. The outer spring (17) may be wound left hander, and the inner spring (16) may be wounded right handed, this arrangement eliminates the possibility of entangling during the motion of springs.

The springs (16) and (17) are guided by means of spring holders (15), which freely rotate around the spring pins (14).This kind of arrangement enables easy rotation of spring holders (15) and hence proper channelizing of spring force on contact (12). The moving contact (12) is supported only by holder arrangement.

When short circuit occurs, the clockwise electromagnetic torque developed between moving contact (12) and fixed contacts (21) and (22) rotates the moving contact (12), as it counteracts the anticlockwise spring torque. As the moving contact (12) crosses the spring dead centre, it flip-locks onto repel position by virtue of free length restoring.

In ON-condition, the torque due to springs is transferred to contact pressure. Whenever contacts wear out, the force of the springs (16) and (17) reduce. In order to maintain constant spring torque, the centre pin (18) which is assembled in moving contact (9) slides freely in the slot in the shaft caps (19and (20). This ensures that the contact pressure does not decrease with erosion. At the same time, the rate of increment in spring torque with length must be more than rate of decrement of spring force. This is achieved by keeping spring rate to lowest possible value. This arrangement provides certain advantages to the structure, few of the advantages are mentioned below:

i. Improved thermal performance due to increase in contact pressure.
ii. Higher electrical life due to ability to perform after erosion.
iii. Option to use less thickness button for material saving.

The shaft end caps (19) and (20) are ultrasonic weld to the shaft (10). So, the shaft (10) has closed protective structure, protecting the components inside during arcing. The shaft end caps (19) and (20) of the shaft assembly (9) have different diameters for circular protrusions given for the purpose of shaft centering, which rotate in the shaft centering holes, of the respective corresponding cassettes (2) and (3) . The shaft centering holes also have different diameters. This assembly poka-yoke is done to prevent assembly of shaft assembly(9) in wrong manner.

The shaft assembly (9) rotates inside the cavity of the cassette (2) and (3). The shaft end caps (19) and (20) have circular protrusion on the outer side as shown in figure below. Assembly poka-yoke is given on the circular protrusion of the shaft caps (19) and (20) and the cassettes (2) and (3), so as to eliminate the possibility of improper insertion of the shaft assembly (9).

A perforated metal sheet,either made of stainless steel or brass called metallic vent, containing uniformly spaced holes of uniform diameter covering half of the total vent area, (23) is inserted in slots given in cassette (2) and (3) as shown in figure.2. These are used in order to de-ionize and thus cool the hot, ionized gases and by-products of arcing.

At one release nut plate (24) is placed in the slot given in the cassettes (2) and (3) beneath the second fixed contact assembly (22) as shown in figure.2. This nut plate (24) secures the second fixed contact assembly (22) onto the outgoing terminal called a CT-link (40) and ensures proper electrical connection between the two. The slot is provided in such a way that the load is transferred from nut plate (24) onto the conductors (22) and (40) and not the plastic cassette material when the nut plate (24) moves up towards the conductor on tightening the electrical joint.

The standard hardware nut (59) trapped inside nut pocket formed by the two cassettes (2) and (3) in the pole module (1)is used for securing mechanical connection between the mech-contact system (36)andthe chassis module (37) as shown in figure 2.The nut pocket is made with sufficient clearance for the nut in such a way that the nut does not rotate too much, but translates up and down.

The two cassettes (2) and (3) are packed together by means of intra-pole steel rivets (26).A high property class standard Allen head bolt (60) is used to secure the electrical connection between the second fixed contact (22)and outgoing terminal (40).

Referring now to figure 8 shows the over-travel indication on cassettes (2) and (3) and the shaft assembly (9). The shaft assembly (9) has Over-travel arrow marking which quantifies the over-travel in degrees given by the mechanism module to the contacts in the pole module (1) as per the marking scheme scale given on the cassettes (2) and (3).This helps in ensuring the required contact pressure. Also, it helps in detection of the exact travel loss of the shaft through mechanism module (27).

Referring now to figure 9 shows the mechanism module (27) as an independent module, mounted on a single pole module (1).The mechanism module (27) drives the shaft assembly by means of drive shaft pins (28) which are inserted on either sides of shaft assembly (9) and lower links (29) of mechanism module (27).Through pins (31) , which will also pass through the shaft assemblies (9) of the other two or three pole modules (1) serve as the coupling between the shaft assemblies (27).

In one implementation, the figure 10 shows the various joining means.These include the mechanical spacer- right (32) and mechanical spacer-left (33) assembled on either sides of shaft assembly which also act as coupling between the shaft assemblies (9) to some extent.

However the main purpose of the mechanical spacer (32) and (33) is to provide proper insulation around the through pins (31), in the space between the pole modules (1), where the through pins (31) come in close proximity with the hot ionized gases escaping through the clearance given between the cassettes (2) and (3) and shaft assembly (9).Also, the mechanical spacer (32) and (33) has kind of fin-like extension on to one side to prevent the possibility of inter pole joining screws (55) getting live. The profile of the mechanical spacer (32) and (33) is designed in such a way so as to interact with mechanical inter lock.

Referring now to figure 10 also shows a cassette coupler (34) used on both the sides of the pole module (1) used for inter-pole mechanical connection, i.e. mechanical connection of three or four pole modules (1) together as illustrated in figure..

The cassette coupler (34) also maintains proper spacing between pole modules (1) on the release side, even if the inter-pole screws (55) are over tightened. Also, the cassette coupler (34) is used to provide mechanical connection between mech-contact system (36), chassis module (37), release module (39) and housing (38) as illustrated in figure.Poka-yoke feature has been provided in the cassette coupler (34) so as to ensure its assembly in right direction.

Referring now to figure10 also shows housing spacers (35) on either side of the pole module(1). The housing spacer (35) is made in such a way that it is used to secure housing to mech-contact system (36) and also to insulate inter pole packing screw (55) from hot ionized gases escaping out from clearance between shaft assembly (9) and cassettes (2) and(3).

Referring now to figure 11, shows a mech-contact system (36). The modular nature of poles allow assembling of two more pole modules (1) along with the pole module (1) with mechanism module (27) mounted on it, to make a mech-contact system (36) for a three pole breaker. Similarly for a four pole breaker, three more pole modules (1) are assembled along with the pole module (1) with mechanism module (27) as shown in figure. Inter-pole stacking screws (55) are used to join three /four poles together.

Referring now to figure 12 shows the assembly of the accessories- UV or shunt release (67) along with the actuator (63), two auxiliary contacts (65) and trip alarm (64), FSD (66) and EOM indicator (68) in the chassis module (37).

The chassis module (37) has rib like features on its vertical walls on its line side, which restricts the translational movement of the mechanism module (27) in horizontal direction. It holds mechanism module (27) in place and thus prevents mechanism module exerting any kind of pressure on the cassettes (2) and (3). The chassis module (37) has integral venting channel which helps in diverting and channelizing the hot ionized gases in right direction and preventing the possibility of a flash over.It also eliminates use of an additional component and ensures ease of assembly.

The chassis module (37) has finger proofing given for release electrical joining screws (60) for the safety of the operator.Aux actuator (42) indicates the status of the breaker by actuating auxiliary contacts (65) and assembled to the mech-contact system (36).

EOM indicator (68) is assembled onto the other side of the breaker which gives the indication of the breaker status for external accessories. The Aux actuator (42) and EOM indicator (68) are prevented from falling out by the housing (38).

Referring now to figure13 shows the exploded view of a basic breaker (57). Standard hardware nuts (59) are inserted in nut pockets provided in the housing (38).The nut pockets are provided with rib like projections on both sides so as to tight fit the nut (59) during transit phase from this assembly point to the final stage. Then the mech-contact system (36) is assembled onto the housing (38).

Self tapping screws (61) are used to secure housing to mech-contact system (36) by means of housing spacer (35) on the incoming side as discussed before. Both the cassettes (2) and (3) have cuts provided on outer surfaces, which guides the ribs given on the side walls of housing (38) on both sides. The housing (38) is thus secured to mech-contact system (36).

The mechanism module (27) may be brought to trip position. The chassis module (37) is secured to the mech-contact system (36) and housing (38) configuration by means of the standard screws (62) andnuts (59) enclosed in nut pockets of pole module (1).

The linear knob (43) is now inserted on top of the fork assembly (30) and held firmly in position by means of snap fit.
Referring now to figure14, shows the exploded view of a micro processor release module (74). The release cover (70) encloses the sensor assembly (71) with the CT links (40) onto the release box (69)and secured to the release box by means of screws (73). The CT links (40) are secured to the release box (69) by means of counter sunk screws (72).The sensor assembly (71) is supported by the release box (70) and freely placed around the CT link(40).

The modular construction of the release module (39) enables connection of a modular thermo magnetic release module (75) to the basic breaker (57) in a similar fashion to form a thermo-magnetic release breaker.

Referring now to figure 15, shows exploded view of full breaker (58). The basic breaker (57) along with the release module (39), either thermo-magnetic or electronic (micro-processor based) make up the full breaker (58).Release mechanical joining screws (56) in the basic breaker (57) are used to secure mechanical connection between the release module (39) and the basic breaker (57), more specifically the mech-contact system (36), chassis module (37), cassette coupler (34) and housing (38). This reduces the number of components involved and gives more rigidity to the entire breaker structure because of the use of a single component for securing means.

If the release unit is electronic release unit, then FSD actuator (44) is mounted in the chassis assembly which interacts with the trip plate of the mechanism module (27).

Referring now to figure 16, shows exploded view of the breaker, wherein the Ingress-protection cover (48), front cover module (47)extended knob(49) and skin (50) is shown. This knob (49) provides a locking for the front cover (47) which ensures its removal only if the circuit breaker mechanism indicates TRIP position.

Referring now to figure17,shows the direct termination nut retainers (51) used for direct or front link or cable lug termination or termination with spreaders.Standard hardware nuts (63) are placed in pockets of termination nut retainers (51).The termination nut retainer assemblies have snap fit which on insertion, goes and locks into cassettes (2) and (3) on incoming side and release module (39) on the outgoing side.

Referring now to figure18, shows the breaker (58) with box clamp nut retainers (53) used for box clamp (52) termination of bare prepared cables.

Referring now to figure19, shows the breaker (58) withtermination of rear terminal short (76) and rear terminal long (77) using rear termination nut retainers (54).

Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features:

One feature of the invention is that, the closed and robust shaft construction provided in the proposed mechanism protects the components within from hot ionized by-products of arcing. An improved thermal and electrical performance due to the contact erosion compensation is provided due to the proposed mechanism. This also gives an option to use button of less thickness for material and cost saving.

Another feature of the invention is that, over-travel indication, a unique feature is provided in the invention. The over travel arrow marking on the shaft assembly quantifies the over travel given by mechanism module to the contacts in degrees as per marking scheme given on cassettes. This ensures the required contact pressure. Also, the exact over travel loss of shaft through the mechanism, if any, is clearly detected.

Another feature of the invention is that, a perforated metallic vents either made of brass or stainless steel, containinguniformly spaced holes of uniform diameter covering half of the total vent area is used in the pole module. These are used so as to de ionize and thus cool the hot ionized gases, particles and other by-products of arcing.

Another feature of the invention is that, rigid plastic structures called as arc deflectors or arc guards, give firm support to the arc-chute assembly. These have ear-like projections which rest on the grooves provided in the cassettes, ensuring that the de-ion plates are intact in their places, even if arc chute lining burns out due to heavy thermal and mechanical stress associated with short circuits, by virtue of its sophisticated structure. The plastic material used for arc deflector is ablative in nature; the design of arc deflectors is in such a way that the ablative material is very much in the zone of arcing. As such, due to ablative action, a low value of let-through energy is ensured.

Another feature of the invention is that, the present invention uses standard nut entrapped in the nut pocket formed by the two cassettes in the pole module for securing mechanical connection between the chassis module and the mech-contact system. The nut pocket is made with sufficient clearance for the nut in such a way that the nut does not rotate too much, but translates up and down.

Another feature of the invention is that, both the shaft end caps of the shaft assembly have different diameters for shaft centering protrusions which rotate in the shaft centering holes, which also have different diameters in the corresponding cassettes. This assembly poka-yoke is done to prevent assembly of shaft assembly in wrong manner.

Another feature of the invention is that, the shaft assemblies are driven by the mechanism module by means of two drive shaft pins which are placed between the adjacent shaft assemblies.

Another feature of the invention is that, the mechanical spacers act as coupling between the shaft assemblies to a fair extent. It provides proper insulation around the through pins in the space between the pole modules, where the through pins come in close proximity with the hot ionized gases escaping through the clearance given between the cassettes and shaft assembly. It also has kind of fin-like extension on to one side to prevent the possibility of inter pole joining getting live.The profile of the mechanical spacer is designed in such a way so as to interact with mechanical inter lock.

Another feature of the invention is that, the cassette couplers are used for inter-pole mechanical connection, i.e. mechanical connection of three or four pole modules together. The cassette coupler also maintains proper spacing between pole modules on the release side, even if the inter-pole screws are over tightened. Also, the cassette coupler is used to providemechanical connection between mech-contact system, chassis module, release module and housing.Poka-yoke feature has been provided in the cassette coupler so as to ensure its assembly in right direction.

Another feature of the invention is that, the housing prevents hot ionized gases from escaping to the bottom and sides and also ensures sufficient clearance andcreep age with the mounting structure and neighboring installations. It also ensures that the aux actuator and EOM indicator in place and not fall out.

Another feature of the invention is that, the housing spacers used on either side of the pole module is made in such a way that it is used to secure housing to mech-contact system and also to insulate inter pole packing screw from hot ionized gases escaping out from clearance between shaft assembly and cassettes.

Another feature of the invention is that, the chassis module has rib like features on the vertical walls on the line side, which restricts the translational movement of the mechanism module in horizontal direction. It holds mechanism module in place and thus prevents mechanism module exerting any kind of pressure on the cassettes.

Another feature of the invention is that, the chassis module has integral venting channel, which helps in diverting and channelizing the hot ionized gases in right direction and preventing the possibility of a flash over. It alsoeliminates use of an additional component and ensures ease of assembly.

Another feature of the invention is that, the chassis module has finger proofing given for release electrical joining screws for the safety of the operator.

Another feature of the invention is that, the knob is secured to the fork assembly by means of a snap fit on the knob which is inserted into the slot given in the fork.

Another feature of the invention is that, the extended Knob provides front cover locking by preventing the removal of front cover when the circuit breaker is in ON position.

Another feature of the invention is that, the release mechanical joining screws in the basic breaker are used to secure mechanical connection between the release module and the basic breaker, more specifically the mech-contact system, chassis module, cassette coupler and housing. This reduces the number of components involved and gives more rigidity to the entire breaker structure because of the use of a single component for securing means.

Although an improved double break low voltage moulded case circuit breaker has been described in language specific to structural features and/or methods, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or methods or devices described. Rather, the specific features are disclosed as examples of implementations of an improved double break low voltage moulded case circuit breaker. Further, it is also understood that the known components and there working is not disclosed in the greater detail in this specification to avoid the complexity of the invention. A person having ordinary skill in the art will be able to understand the working of the know features.
,CLAIMS:1. A circuit breaker (57, 58) either single pole or multi-pole comprises of a pole module (1), at least two cassettes (2, 3), arc chute assemblies (4), shaft assembly (9), a mechanism module (27), a chassis module (37), a housing (38), a shaft assembly (9), a release module (39), and various joining meanscomprises of at least one mechanical spacer (32, 33), characterized in that,
the mechanical spacer (32, 33) includes a fin-like extension on to one side to prevent at least one inter pole joining screws (55) getting live;
a cassette coupler (34) on two sides of the pole module (1) used for inter-pole mechanical connection;
the chassis module (37) havinga rib like features on its vertical walls on a line side, which restricts the translational movement of the mechanism module (27); and
housing spacers (35) on either side of the pole module (1).

2. The circuit breaker (57, 58) as claimed in claim 1, comprises:
a fixed contact assemblies (21, 22);
amoving contact assemblies (11);
at least one spring pin (14); and
at least one spring (16, 17).

3. The circuit breaker (57, 58) as claimed in claim 1 and 2, wherein the pole module (1) comprises of a cassette right (2) and a cassette left (3) for housing contact assemblies (21, 22), wherein said at least two cassettes are made up of thermo-set material.

4. The circuit breaker (57, 58) as claimed in claim 1 to 3, whereinthe rib like features holds mechanism module (27) in place and prevents the mechanism module (27) exerting any kind of pressure on the at least one cassettes (2, 3).

5. The circuit breaker (57, 58) as claimed in claim 1 to 4, wherein the housing spacer (35) is used to secure housing to a mech-contact system (36) and also to insulate an inter pole packing screw (55) from hot ionized gases escaping out from clearance between shaft assembly (9) and the at least one cassettes (2, 3).

6. The circuit breaker (57, 58) as claimed in claim 1 to 5, wherein theat least two cassettes (2, 3) have cavities that hold the contacts and the arc chute assemblies (4) in place, wherein the shaft assembly (9) rotates inside the cavity of the cassette (2, 3).

7. The circuit breaker (57, 58) as claimed in claim 1 to 6, wherein the arc chute assembly (4) comprises of multiple one de-ion plate (5), and at least one plastic component (7, 8), wherein
the de-ion plates (5) are arranged and supported by means of an insulating material, arc-chute lining (6) on either sides, and
said at least one plastic component (7, 8) called arc guard right (7) and arc guard left (8) is fixed onto the arc chute assembly (4) by means of snap-fit provided in said at least one plastic component (7, 8).

8. The circuit breaker (57, 58) as claimed in claim 1 to 7, wherein the mechanism module (27) drives the shaft assembly (9) by means of
a drive shaft pins (28, 31) which are inserted on either sides of shaft assembly (9), and
a lower links (29) of mechanism module (27), wherein the pins (31) passes through the shaft assemblies (9) of the pole module (1) and serve as a coupling between the mechanism module (27).

9. The circuit breaker (57, 58) as claimed in claim 1 to 8, wherein the at least one mechanical spacer (32, 33)comprises of a mechanical spacer- right (32) and a mechanical spacer-left (33) assembled on sides of a shaft assembly (9).

10. The circuit breaker (57, 58) as claimed in claim 1 to 9, whereinthe mechanical spacer (32, 33) provides an insulation around drive shaft pins (31), in the space between the pole modules (1), wherein the drive shaft pins (31) come in close proximity with a hot ionized gases escaping through a clearance given between the at least two cassettes (2, 3) and the shaft assembly (9).

11. The circuit breaker (57, 58) as claimed in claim 1 to 10, wherein the cassette coupler (34) is used to provide mechanical connection between the mech-contact system (36), the chassis module (37), the release module (39) and the housing (38).

12. The circuit breaker (57, 58) as claimed in claim 1 to 11, wherein the chassis module (37) has integral venting channel that helps in diverting and channelizing the hot ionized gases in right direction and preventing the possibility of a flash over.

13. The circuit breaker (57, 58) as claimed in claim 1 to 12, wherein the chassis module (37) has finger proofing given for release electrical joining screws (60) for the safety of the operator.

14. The circuit breaker (57, 58) as claimed in claim 1 to 13 comprises an aux actuator (42) indicating the status of the breaker by actuating auxiliary contacts (65) and assembled to the mech-contact system (36).

15. The circuit breaker (57, 58) as claimed in claim 1 to 14 comprises an EOM indicator (68) assembled onto a side of the circuit breaker (57, 58) which gives the indication of the breaker status for external accessories. The Aux actuator (42) and EOM indicator (68) are prevented from falling out by the housing (38).