Claims:1. An electromagnetic release of a circuit breaker having a fixed contact and a moving contact, wherein said electromagnetic release comprising:
a magnetic frame having a magnetic frame arm;
a coil;
fix core; and
a moving core;
wherein, a first end of said coil, a first end of said magnetic frame, and said fixed contact have common weld joint;
wherein, a second end of said coil, a second end of said magnetic frame and a line terminal have common weld joint;
wherein, said magnetic frame and said coil forms parallel current (I) path.

2. The electromagnetic release as claimed in claim 1, wherein said current (I) flows from said line terminal to load terminal.

3. The electromagnetic release as claimed in claim 2, wherein said current flowing through said coil is I1 and said current flowing through said magnetic frame arm is I2.

4. The electromagnetic release as claimed in claim 3, wherein coil and magnetic frame arm includes at least one resistance, R1 and R2, respectively, to govern said current flowing through said coil and said magnetic frame arm.

5. The electromagnetic release as claimed in claim 1, wherein said magnetic frame is adapted so as to provide increased current path length during short-circuit condition to generate higher voltage drop across electromagnetic release for faster quenching of arc.
, Description:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to a switching devices such as circuit breakers, and particularly, cost effective short-circuit / electromagnetic release of circuit breaker.

BACKGROUND

[002] With the increase of industry size and automation, the requirement of protection devices has also increased. Along with the competitive criterions such as compactness and reliability, cost-effectiveness has also became one of the important criteria. Market has more thrust on compact, reliable and cost effective protection devices.

[003] Generally in thermomagnetic type circuit breakers, apart from contact systems the electromagnetic release has a major cost impact on the total cost of the circuit breaker. An electromagnetic release is consist of magnetic frame, coil, fix core, moving core, plunger and spring. During normal conditions, circuit breaker carries rated current for infinite duration of time. The temperature rise of the circuit breaker line and load terminals should not exceed the limits specified by standards. In order to limit the terminal temperature rise well with in specified limit, the cross section of circuit breaker current path plays crucial role. Apart from contact system, electromagnetic release coil has major impact on the power loss and temperature rise of circuit breaker terminals. Hence, the cross-section of electromagnetic release coil need be optimized in such a way that power loss and temperature rise of circuit breaker should come well within limits specified by the standard. The cost of electromagnetic release has major contribution to the cost of circuit breaker.

[004] The higher cross-section of electromagnetic release coil helps in achieving lesser power loss and temperature rise at circuit breaker terminals. However, higher cross-section increases weight of the coil and subsequently cost of the coil. Hence the requirement of cost effective electromagnetic release and lesser temperature rise at terminal contradicts with each other.

[005] In thermomagnetic circuit breakers, in the event of short-circuit faults electromagnetic releases senses fault current and issues trip command to the operating mechanism.

[006] In prior art circuit breaker described in EP0569652A1 entitled “Magnetic trip mechanism for circuit breaker, equivalent sub-assembly and circuit breakers incorporating them”, wherein Magnetic trip mechanism for circuit breaker is consist of an induction coil which is associated with a moving core with striker and restoring spring inside an insulating sheath and which is mounted longitudinally in a yoke having first and second flanks facing one another. The first flank is fitted with a fixed core within which the striker is guided, the coil being provided with a first end for connecting with the yoke and a second end for connecting with a terminal of the circuit breaker. The trip mechanism furthermore comprises a fixed contact extending into an arc switching electrode. The yoke has a general U shape with a longitudinal arm connecting the two facing flanks and is formed by stamping and bending a metal strip so as to incorporate the fixed contact and the switching electrode. The above magnetic trip mechanism has limitation in generating higher voltage drop during short-circuit fault. Additionally the yoke and fix contact are integrated and are made from same metal strip and hence have limitation in usage for high current rating circuit breakers. As yoke and fix contact are made from ferromagnetic material, they will have higher resistance and are not suitable for high rating circuit breakers.

[007] In prior art circuit breaker described in EP1463082A1, the magnetic tripping device is comprising of a yoke, an induction coil associated with a plunger core with a striker and a return spring. The yoke and circuit breaker terminal are integrated and are made from same ferromagnetic metal strip. The coil is electrically connected to both sides of the yoke. The current flowing from the terminal is thus divided into a first current flowing through the magnetic yoke part stream and a second partial current flowing through the coil. As circuit breaker terminal and yoke are intergraded and forms single component. This helps in reducing number of components and gives advantage of increased mechanical stability in comparison with a structure consisting of several parts and a simplified assembly, particularly in the case of an automated handling assemblies. The above invention has limitation in terms of power loss as the yoke and circuit breaker terminal are made from ferromagnetic material which have relatively higher resistance compared to copper material. Additionally, the construction of magnetic release has limitation in generating higher voltage drop across yoke current carrying stream during short-circuit fault.

[008] In prior art circuit breaker described in FR2629633A1, the magnetic tripping device is comprising of a yoke, an induction coil associated with a plunger core with a striker and a return spring. The yoke and circuit breaker terminal are integrated and are made from same ferromagnetic metal strip. A switching electrode is formed in yoke by providing tongue shaped cut on the yoke base. This switching electrode is used to guide the arc towards arc chute. The object of this invention was to provide compact magnetic release which is constituted by reduced number of parts and to provide preassembled rigid magnetic release whose assembly and installation in circuit breaker housing can be fully automated. The above invention has limitation in terms of power loss as the yoke and circuit breaker terminal are made from ferromagnetic material which have relatively higher resistance compared to copper material.

[009] Thus, in view of the limitations of the existing prior art, there exists a dire need for a cost effective protection release, specifically short-circuit / electromagnetic release. Apart from being cost effective construction, there is also a need for an electromagnetic release which helps in achieving faster short-circuit fault clearing.

SUMMARY OF THE INVENTION

[0010] 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.

[0011] An objective of the present invention is to improve short-circuit performance of the circuit breaker with cost effective design. The performance of the circuit breaker mainly depend upon the performance of the protection release.
[0012] Another objective of the present invention is to provide an method to achieve cost effective electromagnetic release without increasing the power loss and temperature rise of the circuit breaker.

[0013] Yet another objective of the present invention is to use magnetic frame in current carrying path for minimizing the cross-section area of coil.

[0014] Accordingly to one aspect, the present invention provides an electromagnetic release of a circuit breaker having a fixed contact and a moving contact, wherein said electromagnetic release comprising:
a magnetic frame having a magnetic frame arm;
a coil;
fix core; and
a moving core;
wherein, a first end of said coil, a first end of said magnetic frame, and said fixed contact have common weld joint;
wherein, a second end of said coil, a second end of said magnetic frame and a line terminal have common weld joint;
wherein, said magnetic frame and said coil forms parallel current (I) path.

[0015] 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

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:

[0016] Figure 1 illustrates an internal construction of circuit breaker in ON position.

[0017] Figure 2(a) and (b) illustrates an isometric and exploded view of conventional electromagnetic release.

[0018] Figure 3 illustrates an isometric view of conventional electromagnetic release, according to prior art.

[0019] Figure 4 illustrates an isometric view of conventional magnetic frame, according to prior art.

[0020] Figure 5 illustrates an isometric view of electromagnetic release, according to one implementation of the present invention.

[0021] Figure 6 illustrates an isometric view of magnetic frame, according to one implementation of the present invention.

[0022] Figure 7 illustrates a current path through magnetic frame in conventional and improved electromagnetic release during normal operating conditions.

[0023] Figure 8 illustrates a current path through magnetic frame in conventional and improved electromagnetic release during short-circuit condition.

[0024] 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

[0025] 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.

[0026] 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.

[0027] 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.

[0028] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0029] 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.

[0030] 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.

[0031] 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 components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0032] It is also to be understood that the term “module” is used in the specification to indicate an apparatus, unit, component and the like. The term “means” when used in the specification is taken to specify the mode by which desired result is achieved.

[0033] The present invention can be implemented with an electrical switching system that may include but not limited to, circuit breakers or thermo-magnetic breaker, molded case circuit breaker (MCCB) residual circuit breaker (RCB), earth leakage circuit breaker (ELCB), motor protection circuit breaker (MPBC) and the like.

[0034] The circuit breakers consist of a pair of contacts to make and break a circuit. A mechanism is used to make and break the contacts. In healthy circuit condition, contacts can carry a specified current for infinite period of time and can be open or closed by manual means. In abnormal condition such as an overload condition or a relatively high level short circuit condition, a protection release senses abnormality (over current or short circuit fault) and gives the trip command to mechanism in order to separate / open contacts to isolate the faulty circuit from system. Hence, the performance of a circuit breaker in a fault condition depends on the performance of the protection release.

[0035] In the present invention, a cost effective protection release, specifically short-circuit / electromagnetic release is described. Apart from being cost effective construction, this electromagnetic release also helps in achieving faster short-circuit fault clearing.

[0036] The figure 1 illustrates a internal construction of circuit breaker in ON position.

[0037] Figure 2 shows isometric and exploded view of conventional electromagnetic release.

[0038] Figures 3 & 4 illustrates a constructional details of conventional electromagnetic release and magnetic frame, according to prior art. Figures 5 & 6 illustrates an isometric view of electromagnetic release and magnetic frame, according to one implementation of the present invention.

[0039] Figure 7 shows current path in conventional and improved electromagnetic release during normal operating conditions and figure 8 shows current path in conventional and improved electromagnetic release during short-circuit condition.

[0040] List of components as shown in the figures 1-8 are as follows:
1. Moving contact
2. Fixed Contact
3. Knob
4. Line terminal
5. Load Terminal
6. Electromagnetic release
7. Magnetic frame
8. First end of magnetic frame
9. Second end of magnetic frame
10. Parallel path arm of magnetic frame
11. Coil
12. First end of coil
13. Second end of coil
14. Fix core
15. Moving core
16. Plunger
17. Moving core spring
18. Arc
19. Arc root
20. Short-circuit current path through magnetic frame

[0041] In one implementation, as shown in figure 1, in ON condition, the moving contact (1) has made firm contact with fix contact (2) and current flows from Line terminal (4) to load terminal (5).

[0042] In one implementation, as shown in figure-3, first end of coil (12), first end of magnetic frame (8) and fix contact (2) have common weld joint and second end of coil (13) has weld joint with line terminal (4).

[0043] In one implementation, as shown in figure-5, first end of coil (12), first end of magnetic frame (8) and fix contact (2) have common weld joint and second end of coil (13), second end of magnetic frame (9) and line terminal (4) have common weld joint. With this construction, the magnetic frame and coils forms parallel current path.

[0044] In the implementation, as shown in figure-7, the current I, flowing from line terminal will get divided in I1, current flowing through coil, and I2, current flowing through magnetic frame. The coil (11) will have resistance R1 and magnetic frame arm (10) carrying current I2 will have resistance R2. The current distribution through coil and magnetic frame arm (10) will be govern by the values of R1 and R2. The values of R1 and R2 are designed such that the magnetic tripping and temperature rise at terminals of circuit breaker will meet the product standard requirements.

[0045] In the implementation, the reduction in coil current from I to I1 will help in reducing the cross-section area of the coil to the optimum value. Reduction in cross-section area will lead to reduction in weight and cost of the coil. The calibration of electromagnetic release or magnetic tripping threshold of the circuit breaker will be achieved by altering the load values of moving core spring (17).

[0046] In the implementation, the value of equivalent resistance of R1 and R2 will be maintained same as that of conventional electromagnetic release resistance. This will ensure that power loss and temperature rise of circuit breaker remains identical as it was with conventional electromagnetic release. The design of electromagnetic release will help in achieving cost effective circuit breaker which meets the criteria of power loss and temperature rise defined by the standard.

[0047] In the implementation, as shown in figure-8, in the event of short circuit fault, arc roots (19) will be formed on the magnetic frame (7). The voltage drop across magnetic frame will be proportional to length of current path through magnetic frame (20). The improved construction of magnetic frame of improved electromagnetic release gives 2 to 3 times increased current path length as compare to conventional magnetic frame construction. Hence the voltage drop across magnetic frame of present invention will have higher voltage drop which will help in faster built up of arc voltage and superior short-circuit performance.

[0048] Therefore, some of the non-limiting advantages of the present invention, are mentioned below:
• Simplified construction of electromagnetic release suitable for automation
• Use of magnetic frame in current carrying path for minimizing the cross-section area of coil
• In the event of short-circuit fault, electromagnetic release will help for faster arc voltage build up due the construction of magnetic frame which provides increased current path length during short-circuit fault.
• Cost effective design of electromagnetic release. No additional components required for higher arc voltage built up.

[0049] Although a cost effective electromagnetic release of circuit breaker have 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 the cost effective electromagnetic release of circuit breaker.