Claims:1. A circuit breaker assembly comprising:
a rotor being disposed inbetween at least a duality cover means, said rotor having an aperture to receive an anchor pin;
wherein the said rotor is operatively connected to an actuation mechanism of the circuit breaker;
the rotor further comprising at least one moving contact;
wherein the moving contact is secured by inserting the anchor pin through an aperture provided on the moving contact to rotate about the anchor pin;
at least one fixed contact means electrically connected to a terminal for connection to an electric circuit;
a compression spring;
wherein the compression spring provides contact force to maintain pressure between the moving and the fixed contacts;
a spring holder assembly further comprising at least one compression spring assembled on top of at least one metallic holder for contact pressure;
wherein the metallic holder is an elongated member with a substantially broader top end and a comparatively narrower bottom end;
a stopper pin to operatively engage rear end of the metallic holder to the rotor;
a pivot pin to operatively engage rear end of the moving contact and top end of the metallic holder to the rotor;
wherein the compression spring is operatively compressed inbetween the stopper pin and top end of the metallic holder;
wherein the rear end of the moving contact has two apertures to receive the anchor pin and pivot pin;
wherein the anchor pin and the stopper pin are fixed to the rotor cover means;
wherein the pivot pin is free to move with the moving contact; and
wherein once the moving contact crosses dead center, direction of force of the compression spring is operatively reversed.

2. The assembly as claimed in claim 1, wherein said fixed contact means operatively engages with the moving contact to conduct current from the fixed contact means to the moving contact.

3. The assembly as claimed in claim 1, wherein the moving contact is anchored at center of the rotor.

4. The assembly as claimed in claim 1, wherein the moving contact has a substantially broader contoured rear end and a substantially narrower arm protrude.

5. The assembly as claimed in claim 1, wherein the rotor cover means accommodates the spring holder assembly and the rear end of the moving contact, and wherein the arm of the moving contact protrudes externally from the covering means.

6. The assembly as claimed in claim 1, wherein the anchor pin is substantially cylindrical in shape.

7. The assembly as claimed in claim 1, wherein the spring holder preferably comprises a duality of metallic holders.

8. The assembly as claimed in claim 7, wherein one metallic holder is a mirror image of another metallic holder.

9. The assembly as claimed in claim 8, wherein the two metallic holders are optionally joined by means of riveting or crimping.

10. The assembly as claimed in claim 9, wherein the joined metallic holders are substantially Y shaped.

11. The assembly as claimed in claims 1 or 7, wherein the top end of the metallic holder is substantially L shaped and remaining portion is substantially I shaped.

12. The assembly as claimed in claims 1 or 7, wherein the top end of the metallic holder has an aperture for the pivot pin and the rear end of the metallic holder is forked to accommodate the stopper pin.

13. The assembly as claimed in claim 1, wherein short circuiting of the circuit breaker generates an electromagnetic force.

14. The assembly as claimed in claim 13, wherein the electromagnetic force rotates the moving contact.

15. The assembly as claimed in claim 1, wherein the dead center is a critical rotation angle of the moving contact after which direction of a spring force gets reversed across the anchor pin of the moving contact.

16. The assembly as claimed in claim 1, wherein once the compression spring force is reversed, the moving contact rotates in direction of opening and remains there.

17. The assembly as claimed in claim 16, wherein application of a suitable resetting force returns the moving contact below the dead center.

18. The assembly as claimed in claims 1 or 7, wherein the spring holder prevents buckling of springs or misalignment.

19. The assembly as claimed in claim 1, wherein contact pressure is ensured in normal or abnormal conditions.

20. The assembly as claimed in claim 1, wherein current density on the moving contact is reduced and temperature of the circuit breaker is kept under control.
, Description:FIELD OF THE INVENTION

[001] The subject matter of the present invention, in general, relates to protection of circuit breaker components, and more particularly, pertains to a spring based single-break circuit breaker rotary contact arm arrangement.

BACKGROUND OF INVENTION

[002] During operation of power systems, it is often desirable and necessary to switch on or off the various circuits (e.g., transmission lines, distributors, generating plants etc.) under both normal and abnormal conditions. Switching devices are instruments employed for opening and closing an electric circuit. A switching device comprises at least one pole and a control device adapted to open and close said pole. Examples of switching devices include switches and switch-fuses. With advancement of power systems, the lines and other equipment’s operate at very high voltages and carry large currents. The traditional arrangement of switches with fuses cannot serve the desired function in such high capacity circuits.

[003] A circuit breaker can make or break a circuit either manually or automatically under all conditions viz., no-load, full load and short-circuit conditions. The use of circuit breakers is widespread in modern-day residential, commercial and industrial electric systems, and they constitute an indispensable component of such systems toward providing protection against over-current conditions. Various circuit breaker mechanisms have evolved and have been perfected over time on the basis of application-specific factors such as current capacity, response time, and the type of reset (manual or remote) function desired of the breaker.

[004] Switching devices like, Molded Case Circuit Breakers (MCCBs) operating on the current limiting principle typically have a pair of solid stationary electrical contacts joined by a solid moving electrical contact, which provides a path to carry the electrical current in the network. They are typically installed in a distribution load center with other like breakers. Usually multiple MCCBs have a single load center which consists of a sheet metal enclosure with a hinged door that allows access to the face of the enclosed MCCBs. The circuit breakers are secured within an inner sheet metal panel. Electrical busses and conductor raceways are located beneath this inner panel. The MCCBs generally include a molded case main breaker supplying at least one common bus located within the load center.

[005] It is the rotor construction of the double-break arrangement that helps in the better make and break, under normal and abnormal conditions involving very high over-currents. The switching device needs to interrupt an over current arising due to abnormal conditions in the network, as rapidly as possible to minimize damage caused by thermal and mechanical stresses to the equipment installed downstream. It is necessary that the rotor or shaft of the molded case circuit breaker is robust as high electro dynamic repulsive forces are generated between the stationary and moving contacts in the over current conditions.

[006] It is imperative that the rotor should have provisions for providing contact pressure so as to provide the intended repulsion threshold as well as to keep the temperature rise within allowable limit set by the relevant product standards under normal working condition. The moving contact is rotated by a certain angle or distance which is termed as over-travel for attaining the contact pressure. The springs that provide the contact pressure should not be exposed to the arcing, a phenomenon of electrical breakdown of gases which enables the passage of current during contact separation, to prevent the drop-in spring force and ensure contact pressure. The springs are guided by some plastic component.

[007] During the separation of contacts due to repulsion, very high energy is released due to arcing, which results in the erosion of the buttons on both moving contact as well as fixed contact. The rotor should have the provisions for compensating for the erosion so as to maintain the contact pressure even after the erosion of buttons. Moreover, during short circuit due to high current the temperature of moving contacts and springs attains maximum value because of which the plastic components that guide the springs melts thereby resulting in a loss of contact pressure as well as performance of the rotor. The state of art molded case circuit breakers has a rotor/ drive shaft that rotates and switches the electrical circuit.

[008] Reference is made to US 5310971 A, wherein a molded case circuit breaker with contact bridge slowed down at the end of repulsion travel is disclosed. Figure 1 illustrates the detailed perspective view of the movable contact bridge and operating bar. Here, the contact bridge of a molded case circuit breaker is rotatably mounted in a bar by two springs arranged symmetrically from the rotation axis. Each spring is, on the one hand, anchored to the contact bridge, and, on the other hand, anchored to a rod housed in a notch of the bar. The same springs provide contact pressure and slowing-down of opening of the contact bridge at the end of repulsion travel by electrodynamic effect. The contact bridge bears on its edge cam surfaces which, at the end of opening travel, engage the anchoring rods to move them in the notches in the elongation direction of the tension springs. The energy of the contact bridge is thus taken up and stored in the springs causing slowing-down of the contact bridge. The profile of the cams is chosen to enable reclosing of the contact bridge, this reclosing naturally being delayed by the slowing-down effect at the end of travel and also ensures latching of the contact bridge in the open position.

[009] Reference is also made to US 6870112 B2, wherein a low-voltage circuit breaker is disclosed. Figure 2 illustrates the perspective view of the assembly constituted by the moving contact and the contact supporting shaft, for a circuit breaker with double contacts. The low-voltage circuit breaker, comprising: a rotating contact supporting shaft provided with a seat that accommodates the central body of a moving contact so that the first arm protrudes externally from the seat, at least one first spring and one second spring being furthermore arranged in the contact supporting shaft and being suitable to ensure, when the circuit breaker is closed, an adequate contact pressure between the active surface and the fixed contact; the particularity of the circuit breaker consisting of the fact that a first pivot is fixed to the contact supporting shaft and is coupled to a hole formed in the central body, engagement means and at least one second pivot being furthermore arranged on the shaft on mutually opposite sides with respect to the first pivot, the second pivot being movable with respect to the shaft and to the moving contact, the first and second springs being furthermore anchored to the second pivot and to the engagement means and being arranged along two opposite sides of the arm of the moving contact, the second pivot interacting functionally with the first cam-like surface so as to generate a mechanical moment that matches the direction of rotation of the moving contact during at least one portion of the step for separation of the active surface from the fixed contact in a short-circuit condition.

[0010] Reference is also made to US 6262642 B1, wherein a circuit breaker rotary contact arm arrangement. Figure 3 illustrates the front perspective view of a rotary contact circuit breaker interior employing the rotary contact assembly. The rotary contact arrangement for circuit breakers includes a pair of contact springs arranged on each side of a rotary contact arm, as the contact springs interconnect between the rotors and the contact arm via a pair of U-shaped levers. The provision of the U-shaped levers provides uniform contact pressure between both pairs of fixed and moveable contacts to prevent contact erosion.

[0011] Reference is also made to US 6965292 B2, wherein an isolation cap and bushing for circuit breaker rotor assembly. Figure 4 illustrates the perspective view of the circuit breaker with the rotor assembly. The electrically isolated rotor assembly for a cassette assembly of a circuit breaker includes a rotor having a first side and an opposing second side, a first isolation cap disposed on the first side, a second isolation cap disposed on the second side. Each isolation cap preferably includes a centrally located knob with a bushing surrounding each knob, wherein the bushings are sized for securement within apertures within first and second cassette half pieces.

[0012] Reference is also made to US 2012/0298489 A1, wherein a circuit breaker electrical contact assembly, systems and methods for using the same have been disclosed. The electrical contact assembly includes a crossbar, a pivot pin mounted in the crossbar, a contact arm pivotally mounted on the pivot pin and rotatable about a pivot axis, a moveable electrical contact spaced from the pivot axis in a first arm portion of the contact arm, and a spring assembly coupled between the crossbar and the contact arm, the spring assembly including a clevis pin and a spring received on the clevis pin wherein an end of the clevis pin extends through the spring and is received in a pivot recess in the crossbar. This invention pertains to pivot pin like arrangement instead of double-spring holders owing to which it involves a higher number of components and consequently a longer assembly process time. It requires higher spring force to provide specific contact pressure.

[0013] In all the prior art references indicated hereinabove, during short circuit, the moving contact in the rotor starts rotating due to the repulsion forces produced by electromagnetic interaction during short circuit. Simultaneously, an arc is produced between the fixed and moving contacts. For rotation of moving contact with respect to the rotor, there has to be an opening in the rotor with slot length depending on degree of rotation of moving contact. For erosion compensation, there is a slot on the moving contact aligned with the centre of the rotor thereby allowing the contact arm freedom of rotation to compensate for button erosion. Such designs suffer from the following problems, namely:

a. During arcing hot gases and arc products are produced which can enter inside the rotor damaging the components like springs and pins inside the rotor;
b. An open construction leads to lesser differential pressure on arc, i.e. the pressure difference between the front and rear of arc will be lesser. Increased differential pressure is required for efficient driving of arc into the extinguishing zone;
c. An open rotor construction increases the chance of standing arc because of lesser insulation between the contacts; and
d. Slot on the moving contact causes increase in the current density and leads to unnecessary temperature rise.

[0014] While providing adequate protection to high-level over-current conditions, such circuit breakers are overly complex, and difficult to manufacture and service. With respect to their manufacture, for example, the complexity of the control mechanism for separating each set of contacts adds significantly to the overall component part count for the circuit breaker. Consequently, material and assembly costs for such circuit breakers are relatively high.

[0015] These circuit breakers also have power-related disadvantages that are not found in some of the other types of circuit breakers. They typically develop contact resistances that create higher power losses. The power losses fluctuate from one operation to the next, thereby making the them unreliable and burdensome to maintain.

[0016] Therefore, there arises a need for a simple, efficient, effective and robust rotor that does away with problems and disadvantages faced by such conventional circuit breakers. To overcome the drawbacks in rotor designs available, the present invention discloses a robust rotor construction with metal spring holder that provides single break, ensures contact pressure under normal and abnormal working conditions and enhances current breaking.

SUMMARY OF THE INVENTION

[0017] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0018] An object of the present invention is to provide a simple, efficient, effective and robust rotor design that does away with problems and disadvantages faced by such conventional rotors.

[0019] Another object of the present invention is to provide a single-break circuit breaker rotor with enhance contact pressure.

[0020] Another object of the present invention is to provide a cost-effective arrangement that can be used in switchgears, mainly in molded case circuit breakers.

[0021] Another object of the present invention is to provide a rotor arrangement with high speed contact opening having negligible chances of reclosing, improved reliability and longer operational life.

[0022] Another object of the present invention is to provide a rotor assembly that is a screw less arrangement, not requiring any special tools for assembling.

[0023] Another object of the present invention is to provide a robust rotor construction with metal spring holders that provides single-break, ensures contact pressure under normal and abnormal working conditions and enhances current breaking.

[0024] Another object of the present invention is to provide a rotor construction that employs an open rotor construction or partially closed construction.

[0025] Another object of the present invention is to provide a single rotor construction where the components are secluded from damage and the contact pressure is ensured in normal and abnormal conditions.

[0026] Another object of the present invention is to provide the provision for erosion compensation in the rotor cover to reduce the current density on the moving contact and to keep the temperature rise is kept under control.

[0027] Another object of the present invention is to provide a circuit breaker assembly that can be used in all kinds transmission and distribution switchgears with variety of size, shapes and current carrying capacities.

[0028] Another object of the present invention is to provide a circuit breaker assembly that can be used for switchgears with any number of poles/phases.

[0029] Another object of the present invention is to provide a circuit breaker assembly working with only a single compression based spring.

[0030] Another object of the present invention is to provide a cost-effective design of metal spring holders.

[0031] Another object of the present invention is to provide a circuit breaker assembly with high temperature withstanding capabilities of metallic spring holders during short circuit conditions.

[0032] Briefly, the present invention pertains to a robust rotor construction with metal spring holders that provides single-break, ensures contact pressure under normal and abnormal working conditions and enhance current breaking in circuit breakers. It provides a high-speed contact opening of a circuit breaker with negligible chances of reclosing, having improved reliability and longer operational life.

[0033] A circuit breaker assembly is disclosed. The assembly comprises a rotor being disposed inbetween at least a duality cover means, said rotor having an aperture to receive an anchor pin; wherein the said rotor is operatively connected to an actuation mechanism of the circuit breaker; the rotor further comprising at least one moving contact; wherein the moving contact is secured by inserting the anchor pin through an aperture provided on the moving contact to rotate about the anchor pin; at least one fixed contact means electrically connected to a terminal for connection to an electric circuit; a compression spring; wherein the compression spring provides contact force to maintain pressure between the moving and the fixed contacts; a spring holder assembly further comprising at least one compression spring assembled on top of at least one metallic holder for contact pressure; wherein the metallic holder is an elongated member with a substantially broader top end and a comparatively narrower bottom end; a stopper pin to operatively engage rear end of the metallic holder to the rotor; a pivot pin to operatively engage rear end of the moving contact and top end of the metallic holder to the rotor; wherein the compression spring is operatively compressed inbetween the stopper pin and top end of the metallic holder; wherein the rear end of the moving contact has two apertures to receive the anchor pin and pivot pin; wherein the anchor pin and the stopper pin are fixed to the rotor cover means; wherein the pivot pin is free to move with the moving contact; and wherein once the moving contact crosses dead center, direction of force of the compression spring is operatively reversed.

[0034] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0035] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0036] Figure 1 illustrates the detailed perspective view of the movable contact bridge and operating bar according to one implementation of the prior art.

[0037] Figure 2 illustrates the perspective view of the assembly constituted by the moving contact and the contact supporting shaft, for a circuit breaker with double contacts according to another implementation of the prior art.

[0038] Figure 3 illustrates the front perspective view of a rotary contact circuit breaker interior employing the rotary contact assembly according to another implementation of the prior art.

[0039] Figure 4 illustrates the perspective view of the circuit breaker with the rotor assembly according to another implementation of the prior art.

[0040] Figure 5 illustrates the complete shaft assembly with cassette of switchgear according to one implementation of the present invention.

[0041] Figure 6 illustrates the isometric view of the moving contact assembly used in shaft rotor with metal spring holders according to one implementation of the present invention.

[0042] Figure 7 illustrates the cross-sectional view of the moving contact assembly used in shaft rotor in normal condition according to one implementation of the present invention.

[0043] Figure 8 illustrates the cross-sectional view of the moving contact assembly used in shaft rotor at dead center condition according to one implementation of the present invention.

[0044] Figure 9 illustrates the cross-sectional view of the moving contact assembly used in shaft rotor in flipped condition according to one implementation of the present invention.

[0045] Figure 10 illustrates the spring holders used in shaft assembly according to one implementation of the present invention.

[0046] Figure 11 illustrates the exploded view of rotor with spring holder according to one implementation of the present invention.

[0047] Figure 12 illustrates the alternative concept 1 for the spring assembly with metal holder according to another implementation of the present invention.

[0048] Figure 13 illustrates the alternative concept 2 for the spring assembly with metal holder according to another implementation of the present invention.

[0049] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0050] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0051] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0052] The terms and words used in the following description and claims 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 as defined by the appended claims and their equivalents.

[0053] It is to be understood that the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0054] 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.

[0055] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0056] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or component but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0057] The subject invention lies in providing a spring based single-break circuit breaker rotor with enhance contact pressure.

[0058] The present invention pertains to a robust rotor construction with metallic spring holders that provides single-break, ensures contact pressure under normal and abnormal working conditions and enhance current breaking in circuit breakers. It provides a high-speed contact opening of a circuit breaker with negligible chances of reclosing, having improved reliability and longer operational life. The rotor comprises a moving contact connected to a compression spring that provides the requisite contact pressure to the moving contact in ON condition. The spring is supported by the metal holder, and is compressed between a stopper pin and metal holder.

[0059] In one implementation, a simple, efficient, effective and robust rotor design that does away with problems and disadvantages faced by such conventional rotors is provided for.

[0060] In one implementation, a cost-effective arrangement to be used in switchgears, mainly in molded case circuit breakers is provided for.

[0061] In another implementation, a rotor arrangement with high speed contact opening exhibiting negligible chances of reclosing, improved reliability and longer operational life is provided for.

[0062] In another implementation, the rotor assembly is a screw less arrangement, not requiring any special tools for assembling is provided for.

[0063] In another implementation, a robust rotor construction with metal spring holder providing single-break, ensuring contact pressure under normal and abnormal working conditions and enhancing current breaking is provided for.

[0064] In another implementation, a rotor construction that employs an open rotor construction or partially closed construction is provided for.

[0065] In another implementation, a single rotor construction with metal spring holder wherein the components are secluded from damage and the contact pressure is ensured in normal and abnormal conditions is provided for.

[0066] In another implementation, the provision for erosion compensation in the rotor cover to reduce current density on the moving contact and to keep the temperature rise is kept under control is provided for.

[0067] In another implementation, a circuit breaker assembly that may be used in all kinds transmission and distribution switchgears with variety of size, shapes and current carrying capacities is provided for.

[0068] In another implementation, a circuit breaker assembly that can be used for switchgears with any number of poles/phases is provided for.

[0069] In another implementation, a circuit breaker assembly working with a single compression based spring is provided for.

[0070] In another implementation, a cost-effective design of metal spring holders is provided for.

[0071] In another implementation, a circuit breaker assembly with high temperature withstanding capabilities of metallic spring holders during short circuit condition is provided for.

[0072] In another implementation, the spring holder prevents buckling of springs or misalignment by providing requisite holder during the movement of moving contact is provided for.

[0073] Figures 1 to 4 illustrate some state of art rotor designs wherein during short circuit, the moving contact in the rotor starts rotating due to the repulsion forces produced by electromagnetic interaction during short circuit and simultaneously, an arc is produced between the fixed and moving contacts. For the moving contact to rotate with respect to the rotor, there has to be an opening in the rotor with a slot length depending on degree of rotation of moving contact. Erosion compensation is provided by a slot on the moving contact that is aligned with the centre of the rotor thereby allowing the contact arm a freedom of rotation to compensate for button erosion. In such systems, the arcing hot gases and arc products enters the rotor damaging its components, such as springs and pins. The open construction leads to lesser differential pressure on arc. Increased differential pressure is required for efficient driving of arc into the extinguishing zone. Further, an open rotor construction increases the chance of standing arc because of lesser insulation between the contacts. Also, slot on the moving contact causes increase in the current density and leads to unnecessary temperature rise in the circuit breaker.

[0074] To overcome the said drawbacks, Figure 5 illustrates a single-break rotor construction of a circuit breaker with metal spring holders. A compression spring is arranged between two metal holders to provide the necessary contact force during normal and abnormal working conditions to enhance current breaking.

[0075] In particular, a cost-effective arrangement to be used in switchgears mainly in molded case circuit breakers is disclosed. The arrangement provides a high-speed contact opening with negligible chances of reclosing, having improved reliability and longer operational life.

[0076] Figure 5 illustrates the sectional view of a rotor assembly with a cassette 8 in which a rotor 1 can freely rotate in the cassette 8. The rotor consists of a moving contact 7 that is connected to the shaft spring 5. The shaft spring 5 provides the requisite contact pressure to the moving contact 7 in ON condition. The shaft spring 5 is supported by the metal holders 3 and 3A. The shaft spring 5 is compressed between the stopper pin 13 and the metal holder 3 and 3A itself. The moving contact assembly comprises all current carrying elements, such as, moving contact 7, contact button 9, a flexible conductor like braids 6. Cylindrical pin 2 acts as the hinge for the moving contact 7. The pin 2 with the moving contact assembly engages in the profile provided on the shaft housing.

[0077] Figure 6 illustrates the whole rotating shaft assembly that consists of a rotor housing 1, moving contact 7, a compression spring 5 and two spring holders 3 and 3A. This whole shaft assembly will be assembled in an enclosure called cassettes or housing of the circuit breaker. This rotor assembly 1 is driven by an operating mechanism that rotates the rotor in ON, OFF and TRIP conditions. Spring holder 3 and 3A are assembled with moving contact assembly with the pin 12 and 13. Pins 2 and 13 are fixed with shaft housing 1 while pin 12 is free to move with moving contact 7. All the cylindrical pins and the spring holders are free to rotate on their respective axis. Figure 7 illustrates the cross-sectional view of the moving contact assembly used in the rotor assembly 1 in normal condition.

[0078] Whole assembly is screw less arrangement and doesn’t require any special tool for assembly process. The whole arrangement works on the phenomenon of dead center. Dead center is the critical rotation angle of a moving contact after which direction of a spring force gets reversed across the hinge of a moving contact as illustrated in Figure 8. As the moving contact crosses or moves above the dead center, the direction of the spring force gets reversed. Due to reversal of this direction of force, the moving contact rotates in direction of opening and remains there as illustrated in Figure 9, until a resetting force is applied to bring back it below dead center, then it comes to the position as illustrated in Figure 7.

[0079] Figure 8 illustrates the cross-sectional view of the moving contact assembly used in shaft rotor at dead center condition. In this condition, the cylindrical pin 2, stopper pin 13 and moving contact pivot pin 12 are in the same line. After this the contacts get flipped as illustrated in Figure 9 because, as the moving contact crosses over the dead center, the direction of the spring force gets reversed and the moving contact rotates in direction of the opening and remains there.

[0080] Figure 10 illustrates the two metallic holders 3 and 3A that may be joined by means of riveting or crimping or it can be used directly as well. The purpose of introducing these holders is to withstand a high temperature that is attained during short circuit which cannot be sustained by the conventional plastic holders. Moreover, it will also prevent buckling of the compression spring 5 thereby providing proper contact pressure to the moving contact 7.

[0081] Figure 11 illustrates an exploded view of the assembly pattern or sequence by the metal holders 3 and 3A that are assembled in the rotor 1 with the moving contact 7.

[0082] Figures 12 and 13 illustrate two alternative implementations that may be used for the spring holder for 3 and 3A, wherein in both cases, the metal holder is a single component only.

[0083] Some of the important advantages of the present invention, considered to be noteworthy are indicated hereinbelow:

a) It can be used in all kind transmission and distribution switchgears having various size, shapes and current carrying capacities.
b) It can be used for switchgears having any number of poles/phases.
c) It works with single compression based springs.
d) High speed contact opening is achieved with negligible chances of reclosing.
e) Robust and cost effective design of metal spring holders is achieved.
f) High reliability owing to the use of sheet metal components.
g) High temperature withstanding capabilities of the metal spring holder during short circuit condition.
h) Easy of assembly of the metal spring holders.
i) Ease of manufacturing of the metal spring holders.

[0084] Although a simple, efficient, effective and robust rotor design that provides single break, ensures contact pressure under normal and abnormal working conditions and enhances current breaking has been described in language specific to structural features indicated, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or components or devices described therein. Rather, the specific features are disclosed as examples of implementations of a single-break rotor assembly of a circuit breaker with metal spring holders.