Claims:WE CLAIM:

1. A variable thermal release module in a protection device, wherein said module comprising:
at least a bimetal having a fixed and non-bending end, wherein said bimetal is shifted to adjust a relative gap between a trip-plate and said bimetal, to enable tripping of said protection device during an overload fault condition.

2. The module as claimed in claim 1, wherein said bimetal is made of two or more metal stacked together having high and low thermal co-efficient.

3. The module as claimed in claim 1, wherein during said overload fault, said bimetal gets heated and excess heat generated enable said bimetal to deflect and extra deflection is utilized for tripping said protection device.

4. The module as claimed in claim 3, wherein at higher thermal setting, said gap between said trip-plate and said bimetal is more as deflection in said bimetal is more.

5. The module as claimed in claim 4, wherein at low thermal setting, said gap between trip-plate and bimetal is less as deflection is produced by the bimetal is less.

Dated this 30th day of March 2019

Abhishek Sen
Of S. Majumdar & Co.
(Applicant’s Agent)
Registration No. 980
, Description:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to protection devices such as circuit breakers and the like. More particularly, the invention relates to circuit breakers involving a variable thermal setting for overload protection.

BACKGROUND

[002] Switching devices like, circuit breaker provides protection against overload current and also against very high current produced during short circuit. Two types of protection is provided in circuit breaker one is tripping through bimetal based thermal module and other is instantaneous tripping due to magnetic field generation is case of short circuit current.

[003] Circuit breaker typically have at least one solid stationary electrical contact coupled/uncoupled to a solid moving electrical contact, which provides a path to carry or interrupt the electrical current in the network.

[004] Shaft enables holding of electrical moving contact in single/ double break arrangement that helps in make and break of Electrical contacts (Stationary and Fixed) under normal and abnormal conditions (Overload & High current). The shaft of the circuit breaker has to be rotated by operating mechanism for switching molded case circuit breaker (MCCB) ON/OFF. Abnormal condition in the system to be detected by thermal magnetic release, which gives signal to the mechanism for tripping by rotating the Trip-plate, on which the operating mechanism latches.

[005] Thus, it is required that the Switching device should interrupt the high 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.

[006] Reference is made to a prior art US8274355B2, which discloses about the arrangement of components in trip device with direct and indirect heating of the bimetal. Arrangement talks about the bimetal surface connected to different surfaces i.e. line and load surfaces leading to bending of bimetal which is used to give tripping signal to breaker during overload condition.

[007] Reference is further made to US10014142B2, which discloses about the arrangement of components in trip device which can change the relative gap of cross bar and bimetal. Slope provided on cross-bar is used for changing the gap by moving it laterally i.e. left to right, with bimetal in fixed position. Same can be used for providing overload protection at different setting.

[008] Thus, the drawbacks of the existing devices are as follows:
• Lateral shifting of trip-plate for adjusting the air gap between trip-plate and bimetal is limited by Frame-width,
• Location of braid joining, magnetic triggering and thermal triggering in same lateral line leads to insufficient space for providing slope on trip-plate used for adjusting air-gap.
• Shift in lateral position of trip-plate or bimetal due to manufacturing variation can lead to variation in thermal performance of MCCB.

[009] Therefore, there exists a dire need for an a robust variable thermal tripping module in a circuit breaker or MCCB that overcomes the drawbacks as mentioned herein above. Same breaker can be used for different operating load but still can get the desired overload protection. Thermal tripping module senses overload current flowing in the system and actuates accordingly to give signal to the operating mechanism through the trip-plate for opening of MCCB.

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 provide a variable thermal tripping release module in a circuit breaker or MCCB, for overload protection with a provision to sense overload current flowing in the system and actuates accordingly to give signal to the operating mechanism through the trip-plate for opening of the MCCB.

[0012] Another objective of the present invention is to provide a variable thermal tripping release module in a circuit breaker with a provision for holding and moving bimetal correspondingly to adjust the gap between bimetal and trip-plate for achieving adjustable thermal release.

[0013] Accordingly, in one aspect, in one implementation, the present invention provides a variable thermal release module in a protection device. The module comprising: at least a bimetal having a fixed and non-bending end. The bimetal is shifted to adjust a relative gap between a trip-plate and said bimetal, to enable tripping of said protection device during an overload fault condition.

[0014] 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:

[0015] Figure 1 illustrates a side view of thermal release module in maximum setting, according to one implementation of the present invention.

[0016] Figure 2 shows a side view of thermal release module in minimum setting, according to one implementation of the present invention.

[0017] Figure 3 illustrates an exploded view of the thermal system, according to one implementation of the present invention.

[0018] Figure 4 illustrates a top view of the thermal system, according to one implementation of the present invention.

[0019] 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

[0020] 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.

[0021] 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.

[0022] 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.

[0023] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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) and the like.

[0029] In one implementation, the present invention discloses a thermally operated tripping module which is a release with variable thermal setting. At rated current, MCCB is used as the switching device for suppling and isolating the load from supply system. But during the overload fault, the same system of release assembly in breaker, will sense the fault and provide the triggering signal to mechanism to trip the breaker and time required for tripping will be inversely proportional to the overload current.

[0030] In the implementation, during the overload fault, bimetal gets heated and the excess heat generated in the bimetal will deflect it and the extra deflection will be utilized for tripping the mechanism and thus the breaker thereby clearing the fault.

[0031] In the implementation, the breaker has variable thermal setting, which changes the relative gap between the Trip-plate and bimetal. Corresponding gap is to ensure the rotation of trip-plate in overload fault at all the settings of the thermal release. At higher thermal setting, gap between trip-plate and bimetal is more as deflection in the bimetal is more whereas for low thermal setting, gap is less between trip-plate and bimetal as less deflection is produced by the bimetal.

[0032] In the implementation, Bimetal is made of two or more metal stacked together having different thermal co-efficient of each strip i.e. high and low thermal coefficient. Bimetal bend towards the low thermal coefficient on gaining thermal energy after current is passed through it.

[0033] In the implementation, reference is made to figure 1, which shows the side view of thermal release module in maximum setting. The current is being carried through the rear terminal (1) then to bimetal (6) through braid (2). One end of bimetals (6) is fixed in a holder (4). The holder is mounted on a housing through Guiding slot (5). Calibration knob (3) is positioned on closing cover and its limb is trapped in holder slot. The Variable setting is marked on closing cover. Based on the requirement of current, accordingly knob can be aligned to required setting. Stopper for knob rotation is provided on closing cover to avoid over rotation of the knob. Knob limb (9) is attached to holder (4) through cam profile. Rotation of knob (3) will accordingly move the holder in direction which changes the gap (A1 & A2) between trip-plate (8) and thermal screw (7).

[0034] In the implementation, the trip plate (8) of tripping mechanism has fixed rotational requirement to delattch the mechanism. Surface of trip-plate which is being pushed by thermal screw (7) during the overload condition, has slope on its surface, angle of slope is aligned towards the perpendicular to the axis of trip-plate rotation. During overload condition bimetal bends towards the Trip-plate and pushes the triplate, after deflection is more than A1 or A2 based on the thermal setting of the breaker. When overcurrent flows through cantilever bimetal strip, it will get heated and depending on the bimetal temperature-deflection properties it will have temperature rise at which it will bend. Bimetal (6) has threaded hole. Thermal calibration screw (7) is inserted in this hole. When bimetal (6) will produce deflection at overcurrent, thermal screw (7) will move linearly. Linear movement of thermal screw will cause rotational movement of the trip plate (8) and it will delatch the mechanism causing electrical contacts to open and will cut off the current.

[0035] In the implementation, similarly when knob (8) is bought to minimum setting, holder (4) will move upward along with bimetals (6). Trip plate has higher slope in upward direction. Horizontal gap between thermal screw and trip plate will be A2, so less deflection in bimetal at minimum setting is compensated with reduced gap (A2). However, the deflection is sufficient to rotate the Trip plate, required for detaching of mechanism, it operates the contact system by separating the moving contact from the fixed contact and thus clearing of overload fault.

[0036] Some of the novel features of the present invention, are mentioned below:
1) Provision for holding and moving bimetal correspondingly to adjust the gap between bimetal and trip-plate for achieving adjustable thermal release.
2) Engagement of knob with holder, provide linear displacement to bimetal through holder, Holder displacement can be parallel, along the heater (2) or in an angle to the heater surface.
3) Air gap between bimetal and trip-plate, due to slope on trip-plate, is unaffected by the lateral shift (shift along the axial direction of trip-plate) in position of trip-plate or bimetal assembly.

[0037] Although a variable thermal release module in a protection device 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 variable thermal release module in a protection device.