A) TECHNICAL FIELD

[0001] The present invention generally relates to circuit breakers and particularly to current limiting circuit breakers and miniature circuit breakers (MCB). The present invention more particularly relates to a mechanism for determining contact wear in a circuit breaker where the contacts are not readily visible.

B) BACKGROUND OF THE INVENTION

[0002] Circuit interrupters are widely used in domestic, commercial and light industrial installations. Circuit breakers provide protection for electrical systems from electrical fault conditions such as current overloads, short circuits, and low level vohage conditions. Typically, circuit breakers include a spring-powered operating mechanism which opens electrical contacts to interrupt the current through the conductors in an electrical system in response to abnormal conditions. The circuit breaker typically includes a pair of contacts which allows the circuit current to pass from one contact member to another contact member. When the contacts open, the circuit current is prevented from flowing from one contact member to the other and therefore, circuit current is prevented from flowing to a load which is connected to the breaker.

[0003] Circuit breaker contact wear, is a frequently occurring yet difficult to measure problem because it is affected by a variety of factors. The contact wear is affected by the cumulative energy dissipated through arcing as breakers are opened. However, a single severe over-current fault can destroy contacts more quickly than several smaller faults, even though the smaller faults may add up to the same total energy dissipated. For example, some types of faults have more severe effects on contact wear than others, ground faults will destroy contacts more quickly than manual openings. Contacts are not generally easily inspected without costly disassembly and power down. However, if not detected contact wear may result in loss of power.

[0004] In currently existing MCCB provision for contact wear indication is not inbuilt in the circuit breaker. In one of a scheme electronic sensing units to sense the contact wear are externally fitted to the circuit breaker. However, the externally fitted electronic sensing units cannot be used for all poles existing in the circuit breaker as a common unit.

[0005] In switchgear products the contacts wear during normal ON-OFF operation and the life of the contact reduces as the number of operations increases. As the contacts of the circuit are in a closed chamber and the contact wear cannot be viewed by the user. In existing systems the wear of the contact buttons cannot be known unless an electronic unit is provided as add on unit to check the status of the contacts. Thus the customer does not know the status of the circuit breaker since the true picture of contact life cannot be viewed from outside.

[0006] Hence, there exists a need to provide an efficient mechanism for contact wear indication in the circuit breaker to indicate the true status of the contacts when the circuit breaker is in ON condition. Also there exists a need to provide a mechanism to help a user to know the true status of the contacts in each pole of the circuit breaker. Further, there exists a need to provide a mechanism which is reliable and inbuilt in the circuit breaker to determine the contact status in the circuit breaker.

[0007] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and sstudying the following specification.

C) OBJECT OF THE INVENTION

[0008] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0009] The primary object of the present invention is to provide a mechanism for contact wear indication in the circuit breaker to indicate the true status of the contacts when the circuit breaker is in ON condition.

[0010] Another object of the present invention is to provide a mechanism to help a user to know the true status of the contacts in each pole of the circuit breaker.

[0011] Another object of the present invention is to provide a mechanism which is reliable and inbuilt in the circuit breaker to determine the contact status in the circuit breaker.

[0012] Yet another object of the present invention is to provide a mechanism for contact wear indication in a circuit breaker to save critical time lost during replacement of the circuit breaker when the circuit breaker fails to connect to load.

[0013] Yet another object of the present invention is to provide a mechanism for preventive maintenance activity which is carried out by changing either the contacts or the whole circuit breaker when the breaker fails suddenly due to the wear of the contacts.

[0014] Yet another object of the present invention is to provide a mechanism for contact wear indication in a circuit breaker which is less expensive and in turn adding more value to the product arc quenching devices for circuit breakers.

D) SUMMARY OF THE INVENTION

[0015] The various embodiments of the present invention provide a mechanism for contact wear indication in the circuit breaker to indicate the true status of the contacts when the circuit breaker is in ON condition. When the contact button deteriorates due to the impact between the contact buttons or wear out due to the contacts will be indicated thorough the mechanism described herein. Examples of the circuit breaker include but are not limited to a Moulded Case Circuit Breaker (MCCB), a Current limiting circuit breaker and a Miniature circuit breaker.

[0016] In one embodiment of the present invention the MCCB includes an upper casing, a lower casing covering and a knob to turn the MCCB ON and OFF. The MCCB includes at least three contact wear indicators been projected from the upper casing. The three contact wear indicators indicate the contact wear status for three poles of the MCCB. The three poles of the MCCB include three terminals for connecting conductors to the MCCB through a terminal block assembly. Each of the contact wear indicator is provided with a cam at lower end and colour band indications on top of the contact wear indicator. The top portion of the contact wear indicator which is projected from the upper casing of the MCCB has the colour band indication to indicate the user true status of the contacts within the MCCB.

[0017] Each pole of the MCCB includes a cassette coupled to the contact wear indicator. The lower end of the cassette is provided with a retaining spring above which each of the contact wear indicator rests. The retaining spring bring the contact wear indicator to normal position when the MCCB is switched OFF. When the MCCB is switched ON the cam provided in the contact wear indicator comes in contact with the moving contact of each of the pole of the MCCB.

Further, the moving contact is pulled down to an extent until the moving contact rests on the fixed contact in the MCCB.

[0018] The movement of the moving contact is restricted to the thickness of the contact buttons provided on both the moving contact and the fixed contact. During contact wear in any of the contact buttons the moving contact is pushed further down thereby pulling down the contact wear indicator further down due to the spring action. Thus reading on top of the contact wear indicator is changed as indicated by the colour bands during contact wear in the MCCB.

[0019] The mechanism provided in the MCCB circuit breaker is inbuilt in nature to indicate true status of the contacts to a user in each pole of the circuit breaker. The user is updated with the true status of the contacts every time the user switches ON the circuit breaker. Using the mechanism a preventive maintenance activity is carried out by changing either the contacts or the whole circuit breaker with a surprise when the breaker fails suddenly due to the wear of the contacts. The mechanism is simple in arrangement and requires no change in the present assembly of the moulded case circuit breaker. The mechanism is less expensive which in turn adds more value to the product arc quenching devices for circuit breakers. The mechanism saves critical time lost during replacement of the circuit breaker when the circuit breaker fails to connect to load.

E) BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

[0021] FIG. 1 illustrates a side perspective view of a MCCB according to one embodiment of the present invention.

[0022] FIG. 2 illustrates a side perspective view of a contact wear indicator in a cassette according to one embodiment of the present invention.

[0023] FIG. 3 illustrates side perspective view of contact wear indicator for a MCCB according to one embodiment of the present invention.

[0024] FIG. 4 illustrates side perspective view of breaking assembly along with contact wear indicator in an MCCB according to one embodiment of the present invention.

[0025] FIG. 5 illustrates side perspective view of breaking assembly along with contact wear indicator in an MCCB according to one embodiment of the present invention.

[0026] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

F) DETAILED DESCRIPTION OF THE INVENTION

[0027] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.

[0028] The various embodiments of the present invention provide a mechanism for contact wear indication in the circuit breaker to indicate the true status of the contacts when the circuit breaker is in ON condition. When the contact button deteriorates due to the impact between the contact buttons or wear out due to the contacts will be indicated thorough the mechanism described herein. Examples of the circuit breaker include but are not limited to a Moulded Case Circuit Breaker (MCCB), a Current limiting circuit breaker and a Miniature circuit breaker.

[0029] In one embodiment of the present invention the MCCB includes an upper casing, a lower casing covering and a knob to turn the MCCB ON and OFF. The MCCB includes at least three contact wear indicators been projected from the upper casing. The three contact wear indicators indicate the contact wear status for three poles of the MCCB. The three poles of the MCCB include three terminals for connecting conductors to the MCCB through a terminal block assembly. Each of the contact wear indicator is provided with a cam at lower end and colour band indications on top of the contact wear indicator. The top portion of the contact wear indicator which is projected from the upper casing of the MCCB has the colour band indication to indicate the user true status of the contacts within the MCCB.

[0030] Each pole of the MCCB includes a cassette coupled to the contact wear indicator. The lower end of the cassette is provided with a retaining spring above which each of the contact wear indicator rests. The retaining spring brings the contact wear indicator to normal position when the MCCB is switched OFF. When the MCCB is switched ON the cam provided in the contact wear indicator comes in contact with the moving contact of each of the pole of the MCCB. Further, the moving contact is pulled down to an extent until the moving contact rests on the fixed contact in the MCCB.

[0031] The movement of the moving contact is restricted to the thickness of the contact buttons provided on both the moving contact and the fixed contact.

During contact wear in any of the contact buttons the moving contact is pushed further down thereby pulling down the contact wear indicator further down due to spring action. Thus reading on top of the contact wear indicator is changed as indicated by the colour bands during contact wear in the MCCB.

[0032] FIG. 1 illustrates a side perspective view of a MCCB according to one embodiment of the present invention. With respect to FIG. 1 the MCCB 100 includes an upper casing 101, a lower casing 102 and a knob 103 to turn the MCCB ON and OFF. The MCCB includes at least three contact wear indicators 104 been projected from the upper casing. The three contact wear indicators indicate the contact wear status for three poles of the MCCB. The three poles of the MCCB include three terminals 105 for connecting conductors to the MCCB through a terminal block assembly.

[0033] FIG. 2 illustrates a side perspective view of a contact wear indicator in a cassette according to one embodiment of the present invention. With respect to FIG. 2, each pole of the MCCB includes a cassette 201 coupled to the contact wear indicator 104. The lower end of the cassette is provided with a retaining spring above which each of the contact wear indicator rests. The retaining spring 202 bring the contact wear indicator to normal position when the MCCB is switched OFF.

[0034] FIG. 3 illustrates side perspective view of contact wear indicator for a MCCB according to one embodiment of the present invention. With respect to FIG. 3, the contact wear indicator 104 is provided with a cam 301 at lower end and colour band indications 302 on top of the contact wear indicator 104. The top portion of the contact wear indicator which is projected from the upper casing of the MCCB has the colour band indication 302 to indicate the user true status of the contacts within the MCCB. When the MCCB is switched ON the cam provided in the contact wear indicator 104 comes in contact with the moving contact of each of the pole of the MCCB. Further, the moving contact is pulled down to an extent until the moving contact rests on the fixed contact in the MCCB.

[0035] The movement of the moving contact is restricted to the thickness of the contact buttons provided on both the moving contact and the fixed contact. During contact wear in any of the contact buttons the moving contact is pushed further down thereby pulling down the contact wear indicator 104 further down due to spring action. Thus reading on top of the contact wear indicator is changed as indicated by the colour bands 302 during contact wear in the MCCB.

[0036] FIG. 4 illustrates side perspective view of breaking assembly along with contact wear indicator in an MCCB according to one embodiment of the present invention. With respect to FIG. 4 the contact wear indicator 104 is provided with a cam at lower end and colour band indications on top of the contact wear indicator. The top portion of the contact wear indicator which is projected from the upper casing of the MCCB (as shown in FIG. 1) has the colour band indication (as shown in FIG. 3) to indicate the user true status of the contacts within the MCCB. The retaining spring (as shown in FIG. 2) brings the contact wear indicator to normal position when the MCCB is switched OFF. When the MCCB is switched ON the cam 301 provided in the contact wear indicator comes in contact with the moving contact 401 of each of the pole of the MCCB, Further, the moving contact is pulled down to an extent until the moving contact 401 rests on the fixed contact 402 in the MCCB.

[0037] The movement of the moving contact is restricted to the thickness of the contact buttons provided on both the moving contact 401 and the fixed contact 402. During contact wear in any of the contact buttons the moving contact 401 is pushed further down thereby pulling down the contact wear indicator 104 further down due to spring action. Thus reading on top of the contact wear indicator is changed as indicated by the colour bands during contact wear in the MCCB.

[0038] FIG. 5 illustrates side perspective view of breaking assembly along with contact wear indicator in an MCCB according to one embodiment of the present invention. With respect to FIG. 5 the contact wear indicator is provided with a cam at lower end and colour band indications on top of the contact wear indicator. The top portion of the contact wear indicator which is projected from the upper casing of the MCCB (as shown in FIG. 1) has the colour band indication (as shown in FIG. 3) to indicate the user true status of the contacts within the MCCB. The retaining spring (as shown in FIG. 2) brings the contact wear indicator to normal position when the MCCB is switched OFF. When the MCCB is switched ON the cam 301 provided in the contact wear indicator comes in contact with the moving contact of each of the pole of the MCCB. Further, the moving contact is pulled down to an extent until the moving contact rests on the fixed contact in the MCCB.

[0039] The movement of the moving contact is restricted to the thickness of the contact buttons provided on both the moving contact and the fixed contact. During contact wear in any of the contact buttons 501 the moving contact is pushed further down thereby pulling down the contact wear indicator further down due to spring action. Thus reading on top of the contact wear indicator is changed as indicated by the colour bands during contact wear in the MCCB.

G) ADVANTAGES OF THE INVENTION

[0040] The various embodiments of the invention provide a mechanism for contact wear indication in a circuit breaker. The circuit breaker is provided with a mechanism which is inbuilt in nature to indicate true status of the contacts to a user in each pole of the circuit breaker. The user is updated with the true status of the contacts every time the user switches ON the circuit breaker. Using the mechanism a preventive maintenance activity is carried out by changing either the contacts or the whole circuit breaker with a surprise when the breaker fails suddenly due to the wear of the contacts. The mechanism is simple in arrangement and requires no change in the present assembly of the moulded case circuit breaker. The mechanism is less expensive which in turn adds more value to the product arc quenching devices for circuit breakers. The mechanism saves critical time lost during replacement of the circuit breaker when the circuit breaker fails to connect to load.

[0041] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.

[0042] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

CLAIMS

What is claimed is:

1. A contact wear indication mechanism for circuit breakers, the mechanism comprising of: an upper casing, one or more contact wear indicators arranged on the upper casing; a cassette coupled to the one or more contact wear indicators; a lower casing;
a knob to turn the circuit breaker ON and OFF;
Wherein at least one end of the contact wear indicator projecting out from the upper casing include color indications to sense contact wear at ON position thereby indicating the status of the contact in the circuit breaker.

2. The mechanism according to claim 1, further comprising a retaining spring to bring contact wear indicator to a normal position when the circuit breaker is OFF.

3. The mechanism according to claim 1, wherein the one or more contact wear indicators indicate the contact wear status for a plurality of poles of the circuit breaker.

4. The mechanism according to claim 1, wherein the plurality of poles of the circuit breaker include at least one terminal for connecting conductors through a terminal block assembly.

5. The mechanism according to claim 1, wherein each of the contact wear indicator is provided with a cam at a lower end.

6. The mechanism according to claim 1, wherein each of the contact wear indicator
includes colour band indications on top of the contact wear indicator.

7. The mechanism according to claim 1, wherein the lower end of the cassette is provided with a retaining spring above which each of the contact wear indicator rests.

8. The mechanism according to claim 5, wherein the cam provided in the contact
wear indicator comes in contact with a moving contact of each of the pole when
the circuit breaker is ON.

9. The mechanism according to claim 8, wherein the moving contact is pulled
down to an extent until the moving contact rests on the fixed contact in the circuit
breaker.

10. The mechanism according to claim 8, wherein a movement of the moving
contact is restricted to the thickness of the contact buttons provided on both the
moving contact and the fixed contact.

11. The mechanism according to claim 1, wherein the reading on top of the contact wear indicator is changed as indicated by the colour bands during contact wear in the circuit breaker.