F0RM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - AN IMPROVED MODULAR SINGLE POLE
THERMAL MAGNETIC RELEASE UNIT FOR MOULDED CASE CIRCUIT BREAKER
2. Applicant(s)
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company.
(c)ADDRESS: L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE NVENTION
The present invention relates to an improved modular single pole thermal magnetic release unit for moulded case circuit breaker. More particularly, the invention is concerned about a thermal and magnetic actuation unit for a moulded case circuit breaker whereby the said unit can be easily attached and detached from the housing of the circuit breaker. The invention is concerned about improvement in life of MCCB contact buttons and hence MCCB life by provision of separate verification/calibration of the modular unit during MCCB manufacturing. The invention is also concerned about improvement in performance of thermal actuation system by provision of enclosed geometry of the module and improvement in efficiency of magnetic actuation system by having non magnetic parts for the assembly of the same.
BACKGROUND OF THE INVENTION
US 5,381,120 document discloses a molded case circuit breaker thermal-magnetic trip unit is adapted to respond to a mechanical rating plug that sets the travel distance between the operating mechanism trip initiating bar and the bimetal associated with the thermal-magnetic trip unit.
US 4,080,582 document discloses a single-pole circuit breaker or a plural-pole circuit breaker of the type having a common trip bar extending between poles whereby any pole tripping acts there through to trip the other pole or poles. The breaker is provided with an improved trip mechanism comprising a subassembly for each pole wherein all of the thermal and magnetic trip elements are mounted on a breaker terminal plate that acts as a base therefore and which is secured to the breaker housing. One of the objects of this document is to provide a circuit breaker with an improved thermal and magnetic trip subassembly.
KR 20040003596 document discloses a trip part structure of a molded case circuit breaker is provided to prevent a damage of load elements due to the rush current by shorting a tripping time according to a bending operation of a bimetal. The trip part structure of a molded case circuit breaker includes a bimetal and a trip bar. The bimetal is bent to one direction when the thermal deformation is generated by the rush current. The trip bar is used for opening a line

path when the bimetal is bent to one direction. The trip part structure of a molded case circuit breaker further includes a magnetic body. The magnetic body is installed to the bent direction of the bimetal. A fixed end of the bimetal and one end of the magnetic body are formed with one body,
US 6,087,914 document discloses a trip mechanism, including two trip actuators, namely a bi-metal trip actuator and a magnetic trip actuator, that act on a plunger. A plunger-guide guides motion of the plunger along a straight line path of travel. Each trip actuator is capable of moving the plunger independently of the other trip actuator to cause the circuit breaker to trip in response to detection of either a thermal fault or a magnetic fault.
The problem in the prior art is during manufacturing of the MCCB, verification and testing of the thermal-magnetic release with MCCB damages the contact buttons of the MCCB which decreases the electrical life of the MCCB,
Thus, there is a need to provide an improvement over the existing single pole modular thermal magnetic type trip units used with MCCB. The present invention doesn't involve any part of the MCCB's mechanism. This invention overcomes the problem as this damage is avoided by verifying the performance of the thermal-magnetic release module by pre-testing the same on a separate test setup before assembly with the MCCB thus improving the life of the MCCB
OBJECTS OF THE INVENTION
An object of the present invention is to overcome the problems/disadvantages of the prior art.
Another object of the present invention is to provide an improved modular single pole thermal magnetic release unit for moulded case circuit breaker,
Yet, another object of the present invention is to provide an attached/detached modular single pole thermal magnetic release unit for moulded case circuit breaker.

Yet another object of the present invention is to have provision of separate verification/calibration of the modular unit during MCCB manufacturing.
Yet another object of the present invention is to have improvement in thermal actuation system by having enclosed geometry of the module.
Yet another object of the present invention is to improve efficiency of the magnetic actuation system by using non magnetic parts for the assembly of the same.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an improved modular
single pole thermal magnetic actuation unit for tripping a moulded case circuit breaker, said
unit being replaceably mounted on a moulded case circuit breaker, said unit comprising:
a housing;
plurality of means located in said housing for sensing abnormal condition, said means
comprising thermal actuation system and/or magnetic actuation system;
means for attaching/detaching said unit to/from the moulded case circuit breaker
wherein said means for attaching and/or detaching the said unit to/from with said moulded
case circuit breaker comprises plurality of rib means adapted to get operatively
engaged/disengaged with/from cavity means provided in the said moulded case circuit
breaker and a bottom protrusion means adapted to get operatively engaged/disengaged
with/from hole means provided in the said moulded case circuit breaker
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 illustrates Single pole modular thermal magnetic release unit of the present invention.
Fig 2 illustrates Cut view of single pole modular thermal magnetic release
Fig 3 illustrates Cut view of MCCB showing the region where the module is placed
Fig 4 illustrates Enlarged view of MCCB showing the region where the module is placed
Fig 5 illustrates Cut view of single pole modular thermal magnetic release showing different
parts

Fig 6 illustrates Exploded view of the single pole modular thermal magnetic release
Figures 7and 8 illustrate Single pole modular thermal magnetic release unit of the present invention incorporated in the housing of a moulded case circuit breaker.
Fig 9 illustrates Single pole modular thermal magnetic release unit of the present invention detached from the housing of a moulded case circuit breaker.
Fig 10 illustrates a graph representing MCCB's electrical life v/s verification or calibration shots
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
According to the invention there is provided a single pole modular thermal magnetic release, as shown in figures 1 and 2, used for tripping a MCCB during abnormal electrical conditions. It involves a thermal & magnetic type actuation system which senses any abnormal electrical conditions such as overload & short circuit and is assembled as a module for each pole with the help of housing (10). The module gets assembled to current carrying path of each pole of the MCCB as shown in figures 3 and 4. The tripping operation of the MCCB is by rotating a trip bar in the MCCB's mechanism by this module's actuation system which disengages the latching components & trips the breaker's mechanism.
Figure 5 illustrates the cut view of single pole modular thermal magnetic release having different parts. The thermal actuation is through a bimetal means (4) and screw means (5) arrangement attached to a current carrying conductor means (1) through rivets means which bends during overload condition due to heat produced by the current carrying conductor (1) and pushes the trip bar in the MCCB's mechanism tripping the MCCB.
The enclosed chamber of the module improves the heat absorption capability of the thermal actuation system by reducing the heat losses occurring due to natural heat convection through air. Due to the enclosed geometry of the module the resulting heat flow through the module is such that the heat absorption by the bimetal (4) is improved which increases the consistency of the thermal actuation system substantially.
Fig 6 illustrates the exploded view of the single pole modular thermal magnetic release assembly. The magnetic actuation system consists of fixed magnet means (12) attached to the

same current carrying conductor (1) through rivets (11) and a moving magnet means (9) arrangement which gets attracted towards the fixed magnet (12) whenever any short circuit condition occurs. The fixed magnet (12) comprises a substantially U-shaped profile which attracts the moving magnet (9) during an abnormal condition. The moving magnet arrangement consists of a moving magnet (9) attached to a non magnetic bracket means (6) through rivets (8). The attraction force on the moving magnet arrangement is produced by electromagnetic effect due to current flowing in the current carrying conductor (1). The exact current threshold is set by the opposing force of two tension springs means (3) attached to the moving magnet arrangement and a pin means (2) assembled in the module. The movement of the moving magnet (9) pushes the trip bar in the MCCB's mechanism thereby tripping the MCCB.
Presence of any magnetic part in the vicinity of the magnetic actuation system will leak some flux out of the magnetic path. Higher the leakage flux, lesser will be the efficiency of the magnetic actuation system. In the present invention the magnetic actuation system has less leakage flux due to absence of any magnetic part in the vicinity of fixed & moving magnet. The parts used for assembling and supporting fixed and moving magnet assembly are made of non-magnetic material. Due to this, the flux leakage outside the magnetic path is reduced and flux linkages are increased. Due to less leakage and increased flux linkages the efficiency of the magnetic actuation system is improved in the present invention.
According to an embodiment of the invention, the unit comprises ribs means (13) and bottom protrusion means (14) provided in the housing of the module which fits in the cavity and hole provided in the MCCB housing. The ribs and protrusions are designed to fit with the ergonomics of the cavity and the hole provided in the circuit breaker housing. Figures 7 and 8 illustrate single pole modular thermal magnetic release unit of the present invention incorporated in the housing of a moulded case circuit breaker. After fitting this modular release in the MCCB housing using the ribs and protrusion, the breaker's current path is closed by attaching current carrying conductor in the module with that of the MCCB using screws as shown in figures 3 and 4. Figure 9 illustrates single pole modular thermal magnetic release unit of the present invention detached from the housing of a moulded case circuit breaker. To detach this module from the MCCB, the procedure described above is followed in the reverse way i.e. the current path is first opened by unscrewing, followed by simply

pushing the module's bottom protrusion and then pulling the module up from the MCCB housing.
The total assembly of the thermal and magnetic actuation system is assembled as a separate single pole module with the help of housing. This can be assembled isolately from rest of MCCB components including MCCB mechanism which present designs lack. The modules can be separately tested on a dummy MCCB before assembly with the MCCB if desired. This will reduce the testing time & damage to MCCB contacts caused during the tests & also reduces assembly time of MCCB.
For example, consider two thermal magnetic releases; one is an integrated part of the MCCB and other with modular type of construction as in this invention which can be separately tested without being assembled with MCCB. Calibration/verification shots on MCCB to check performance of thermal magnetic release erodes the contact buttons of the MCCB which decreases the life of the MCCB. Higher the no of shots, higher will be contact erosion and hence higher will be the reduction in MCCB electrical life. As against this, in this invention, the thermal magnetic release which is assembled as a single pole module can be separately tested on a separate test setup which doesn't include the MCCB in which it will be assembled. After calibration/verification of the performance of the release, It is assembled with the MCCB thus avoiding any erosion of MCCB's contact buttons and hence any reduction in MCCB electrical life. This is presented in the form of graph in figure 10.
ADVANTAGES OF THE INVENTION
The advantages of the present invention are as follows:
a. Can be separately assembled without MCCB
b. Assembles with MCCB as a module
c. Saves assembly time of MCCB
d. Doesn't involve any of the MCCB's mechanism parts.
e. Can be separately tested before assembly with MCCB
f. Can be replaced with another module easily
g. Simple arrangement of parts.
h. Less no. of parts
i. Heat losses in thermal actuation system are reduced

j. Better consistency due to increased efficiency of actuation systems
The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. The conductor, pin, spring, bimetal, magnet, screw and rivet as stated do not limit the scope of the present invention. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.

We Claim
1. An improved modular single pole thermal magnetic actuation unit for tripping a moulded case circuit breaker, said unit being replaceably mounted on a moulded case circuit breaker, said unit comprising: a housing;
plurality of means located in said housing for sensing abnormal condition, said means comprising thermal actuation system and/or magnetic actuation system; means for attaching/detaching said unit to/from the moulded case circuit breaker; wherein said means for attaching and/or detaching the said unit to/from with said moulded case circuit breaker comprises plurality of rib means adapted to get operatively engaged/disengaged with/from cavity means provided in the said moulded case circuit breaker and
a bottom protrusion means adapted to get operatively engaged/disengaged with/from hole means provided in the said moulded case circuit breaker.
2. The unit as claimed in claim 1, wherein said housing is made of non conducting and non magnetic material means.
3. The unit as claimed in claims 1 and 2 further comprising other non magnetic parts adapted to reduce magnetic flux leakage.
4. The unit as claimed in claim 1, wherein said thermal actuation system comprising: bimetal means;
conductor means;
fastener means;
wherein said bimetal means being adapted to attached to said conductor means
through said fastener means; said bimetal means being bent during abnormal
condition and pushing said trip bar means.
5. The unit as claimed in claim 1 , wherein said magnetic actuation system comprising:
fixed magnet means;
moving magnet arrangement;

non magnetic bracket means;
wherein said fixed magnet means being attached to said conductor means through said
fastener means;
wherein said moving magnet arrangement comprising: moving magnet means being
attached to said non magnetic bracket means through said fastener means; said
moving magnet means being attached to plurality of spring means for setting
threshold current value and a pin means adapted to said unit; and
wherein said fixed magnet means having a substantially U-shaped profile such that it
attracts said moving magnet means thereby providing resting surface for said moving
magnet means over the said U-shaped profile during abnormal condition..
6. The unit as claimed in any of the preceding claims adapted for verification or calibration of performance of thermal magnetic release so as to improve life of moulded case circuit breaker.
7. The unit as claimed in any of the preceding claims having enclosed chamber geometry adapted for improved heat absorption.
8. An improved modular single pole thermal magnetic actuation unit for tripping a moulded case circuit breaker as herein substantially described and illustrated with the accompanying drawings.