Claims:1. A circuit breaker assembly comprising:
a rotor being disposed inbetween at least two cover means, said rotor having an aperture so as to receive a central anchor pin;
wherein the said rotor is operatively connected to an actuation mechanism of the circuit breaker;
the rotor further comprising one or more moving contact;
wherein the moving contact is secured by inserting the central anchor pin through an aperture provided on the moving contact to rotate about the central anchor pin;
one or more fixed contact means electrically connected to a terminal for connection to an electric circuit;
wherein said fixed contact means operatively engages with the moving contact so as to conduct current from the fixed contact means to the moving contact;
a compression spring;
wherein the compression spring provides contact force to maintain pressure between the moving and the fixed contacts;
a moving contact cover insulating the moving contact;
a spring holder assembly further comprising at least one compression spring assembled between a duality of pins for contact pressure;
a duality of spring holders providing guide during rotation of the moving contact;
wherein a spring is assembled between the duality of spring holders;
wherein limb of one spring holder fits into limb of the other spring holder to ensure alignment of the duality of spring holders
a duality of rotor covers;
wherein the rotor cover isolates the rotor assembly; and
wherein the rotor cover and the moving cover isolates spring chamber from arcing.

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

3. The assembly as claimed in claim 2, wherein the moving contact has a contoured central body of which a pair of substantially symmetrical arms protrudes.

4. The assembly as claimed in claim 1, wherein the rotor is provided with a seat that accommodates the central body of the moving contact so that the arms of the moving contact protrudes externally from the seat.

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

6. The assembly as claimed in claim 1, wherein the electromagnetic force rotates the moving contact to repelled position.

7. The assembly as claimed in claim 4, wherein at repelled position an arc is generated.

8. The assembly as claimed in claim 1, wherein the duality of spring holders prevents buckling of springs or misalignment of spring holders.

9. The assembly as claimed in claim 1, wherein rotor assembly is secluded from damage.

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

11. The assembly as claimed in claim 1, wherein the rotor cover provides erosion compensation.

12. The assembly as claimed in claim 1, wherein current density on the moving contact is reduced and the temperature 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 rotor spring holder for double-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] Another type of circuit breaker, referred to as a "double-break" circuit breaker, includes two sets of current-breaking contacts to accommodate a higher level of over-current conditions. The double-break circuit breaker implements its two sets of contacts using the respective ends of an elongated rotatable blade as movable contacts which meet non-movable contacts disposed adjacent the non-movable contacts. The non-movable contacts are located on the ends of respective U-shaped stationary terminals, so that an electro-magnetic blow-off force ensues when the current, exceeding the threshold level, passes through the U-shaped terminals. Thus, when this high-level over-current condition is present, the blow-off force causes the elongated rotatable blade to rotate and the two sets of contacts to separate simultaneously.

[006] 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.

[007] 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.

[008] 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. Currently, all molded case circuit breaker have a rotor/drive shaft that rotates and switches the electrical circuit.

[009] 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.

[0010] 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.

[0011] 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.

[0012] Reference is further 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.

[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 double-break 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 the first-described (single-break) circuit breaker. These double-break circuit breakers typically develop contact resistances which create higher power losses. The power losses fluctuate from one operation to the next, thereby making the double-break circuit breaker 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 that provides double 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 double-break circuit breaker rotor spring holder with enhance contact pressure.

[0020] Another object of the present invention is to provide a robust rotor construction that provides double break, ensures contact pressure under normal and abnormal working conditions and enhances current breaking.

[0021] Another object of the present invention is to provide a rotor construction that employs an open rotor construction or partially closed construction.

[0022] 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.

[0023] 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.

[0024] Briefly, the present invention pertains to a robust rotor construction that provides double break, ensures contact pressure under normal and abnormal working conditions and enhance current breaking in circuit breakers. A moving contact cover provides insulation to the moving contact from the arc and its products. A rotor cover isolates the spring chamber from the arcing zone and the moving contact cover that provides insulation to the moving contact also aids the rotor cover in isolating the spring chamber. This closed single rotor construction secludes the components from damage while ensuring that contact pressure is provided for both normal and abnormal conditions.

[0025] A circuit breaker assembly is disclosed. The assembly comprises a rotor being disposed inbetween at least two cover means, said rotor having an aperture so as to receive a central anchor pin; wherein the said rotor is operatively connected to an actuation mechanism of the circuit breaker; the rotor further comprising one or more moving contact; wherein the moving contact is secured by inserting the central anchor pin through an aperture provided on the moving contact to rotate about the central anchor pin; one or more fixed contact means electrically connected to a terminal for connection to an electric circuit; wherein said fixed contact means operatively engages with the moving contact so as to conduct current from the fixed contact means to the moving contact; a compression spring; wherein the compression spring provides contact force to maintain pressure between the moving and the fixed contacts; a moving contact cover insulating the moving contact; a spring holder assembly further comprising at least one compression spring assembled between a duality of pins for contact pressure; a duality of spring holders providing guide during rotation of the moving contact; wherein a spring is assembled between the duality of spring holders; wherein limb of one spring holder fits into limb of the other spring holder to ensure alignment of the duality of spring holders a duality of rotor covers; wherein the rotor cover isolates the rotor assembly; and wherein the rotor cover and the moving cover isolates spring chamber from arcing.

[0026] 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

[0027] 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:

[0028] Figure 1 illustrates the detailed perspective view of the movable contact bridge and operating bar according to one implementation of the prior art.

[0029] 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.

[0030] 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.

[0031] Figure 4 illustrates the perspective view of the circuit breaker with the rotor assembly according to another implementation of the prior art.

[0032] Figure 5 illustrates the MCCB contact system in ON condition according to one implementation of the present invention.

[0033] Figure 6 illustrates the moving contact in repelled position according to one implementation of the present invention.

[0034] Figure 7 illustrates the description and arrangement of the shaft component according to one implementation of the present invention.

[0035] Figure 8 illustrates the how spring holder assembly arranged in the shaft to get desire contact pressure according to one implementation of the present invention.

[0036] Figure 9 illustrates the arrangement of spring holders to prevent spring buckling and alignment of spring holder to achieve higher and balanced contact pressure according to one implementation of the present invention.

[0037] 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

[0038] 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.

[0039] 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.

[0040] 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.

[0041] It is to be understood that the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] The subject invention lies in providing a double-break circuit breaker rotor spring holder with enhance contact pressure.

[0046] The present invention pertains to a robust rotor construction that provides double break, ensures contact pressure under normal and abnormal working conditions and enhance current breaking in circuit breakers. A moving contact cover provides insulation to the moving contact from the arc and its products. A rotor cover isolates the spring chamber from the arcing zone and the moving contact cover that provides insulation to the moving contact also aids the rotor cover in isolating the spring chamber. This closed single rotor construction secludes the components from damage while ensuring that contact pressure is provided for both normal and abnormal conditions.

[0047] 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.

[0048] In another implementation, a robust rotor construction providing double break, ensuring contact pressure under normal and abnormal working conditions and enhancing current breaking is provided for.

[0049] In another implementation, a rotor construction that employs an open rotor construction or partially closed construction is provided for.

[0050] In another implementation, a single rotor construction wherein the components are secluded from damage and the contact pressure is ensured in normal and abnormal conditions is provided for.

[0051] 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.

[0052] In another implementation, current conduction in the circuit breaker happens from the first fixed contact to the moving contact and finally to second fixed contact is provided for.

[0053] In another implementation, compression spring arranged between holders, provides the contact force required to maintain the pressure between moving and fixed contacts at desired levels.

[0054] In one implementation, a moving contact cover insulating the moving contact from arc and its products is provided for.

[0055] In another implementation, a rotor cover isolating the spring chamber from arcing zone and the moving contact cover isolating the spring chamber is provided for.

[0056] In another implementation, the rotor or shaft that carries a minimum of one contact arm, alternately called a moving member or moving contact, is provided for.

[0057] In another implementation, rotor covers covering the rotor in a closed assembly is provided for.

[0058] In another implementation, assembling of the springs for contact pressure in the spring holders is provided for.

[0059] In another implementation, anchoring of the moving contact at center of the rotor is provided for.

[0060] In another implementation, securing the location of the contact arm through insertion of a central anchor pin through a hole on the moving contact aligned with the center of the rotor to allow the contact arm freedom of rotation within a predetermined locus about the said central anchor pin is provided for.

[0061] In another implementation, a spring holder assembly carrying at least one compression spring assembled between a pair of pins to achieve the desired contact pressure is provided for.

[0062] In another implementation, the spring holders preventing buckling of springs or misalignment of spring holders by providing requisite guide during the movement of moving contact is provided for.

[0063] 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.

[0064] To overcome the said drawbacks, Figure 5 illustrates the double-break circuit breaker of the present invention with contact system in ON condition. The current conduction happens through the fixed contact onto the moving contact and again to the second fixed contact. A compression spring is arranged between the holders to provide the contact force required to maintain the pressure between moving and fixed contacts at desired levels.

[0065] The contacts are designed (as in most of present MCCBs) in a manner that during short circuit conditions, an electromagnetic force acts between the moving contact and the fixed contacts. This force rotates the moving contact and brings it to the repelled position as illustrated in Figure 6. While the moving contact moves to the repelled position, arcing happens as a result, arc products and hot gases are produced. The moving contact cover provides insulation for moving contact from the arc and its products. The rotor cover isolates the spring chamber from the arcing zone and the moving contact cover is designed to aid it in the isolation of the spring chamber.

[0066] Referring to Figure 7, wherein a rotor or shaft 1 that carries a minimum of one contact arm 2, alternately called a moving member or moving contact, is illustrated that it forms the rotary actuating structure. The rotor is functionally connected to an actuation mechanism of the circuit breaker and is provided with a seat that accommodates the central body of the moving contact 2 in a manner that the two symmetrical arms of the moving contact 2 protrude externally from the rotor seat 1. The moving contact 2 is anchored at center of the rotor. The rotor covers 3a, 3b gives the rotor a closed assembly. The springs that provide the contact pressure are assembled in the spring holders 7a, 7b.

[0067] The moving contact 2 is anchored at center of the rotor. The location of the contact arm 2 is secured through insertion of the central anchor pin 7 through a hole 6 on the moving contact 2 aligned with the center of the rotor thereby allowing the contact arm 2 freedom of rotation within a predetermined locus about the said central anchor pin 5.

[0068] Referring to Figure 8, the spring holder assembly 8 that carries minimum one compression spring 4, is assembled between the set of two pins 9 to achieve the desired contact pressure. Buckling of springs or misalignment of spring holders causes loss in contact pressure. Telescopic construction of spring holders is illustrated in Figure 5. The spring holders 7a, 7b prevents buckling of springs or misalignment of spring holders by providing the requisite guide during the movement of moving contact.

[0069] Referring to Figure 9, spring 4 is assembled between spring holder 7a, 7b. Limb “b” as illustrated in Figure 9 or of any shape in spring holder 7b goes inside the limb “a” as illustrated in Figure 5 or of any shape in spring holder 7a which makes it a telescopic construction that ensures alignment of spring holders throughout the motion and also prevent the buckling of springs.

[0070] Significantly, in the enclosed single rotor construction of the present invention, the components are secluded from damage and the contact pressure is ensured in both normal and abnormal conditions. Further, by providing a provision for erosion compensation in the rotor cover, current density on the moving contact is reduced and the temperature rise is in the circuit breaker is kept under control.

[0071] Some of the important advantages of the present invention, considered to be noteworthy are indicated hereinbelow:

a) The double-break circuit breaker rotor spring holder has a robust design;
b) The double-break circuit breaker rotor spring holder insulates the spring;
c) The double-break circuit breaker rotor spring holder prevents buckling of springs; and
d) The double-break circuit breaker rotor spring holder ensure desired contact pressure in the circuit breaker.

[0072] Although a simple, efficient, effective and robust rotor design that provides double 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 double-break circuit breaker rotor spring holder.