A) TECHNICAL FIELD
[0001] The present invention generally relates to electrical switching
apparatus and particularly to circuit breakers. The present invention more particularly relates to thermo-magnetic release in moulded case circuit breakers and the auto temperature compensation in thermo-magnetic releases.
B) BACKGROUND OF THE INVENTION
[0002] Electrical switching apparatus, such as circuit breakers, are
employed in diverse capacities in power distribution systems to provide protection for electrical equipment from electrical fault conditions such as current overloads, short circuits, abnormal level voltage conditions etc.
[0003] A number of circuit breakers are known in which a bimetallic
element responds to an overcurrent through the breaker by physical deformation so as to trip the breaker, thereby interrupting the current. The breaker includes a pivoted contact arm carrying one of the contacts of the breaker. A bimetallic strip carries the other contact of the breaker. When an overcurrent passes through the bimetallic strip, it deforms urging the contact arm to move against the bias of an overcenter spring. When the bimetallic element forces the pivoted contact member past the overcenter point, the breaker snaps open, breaking the circuit.
[0004] Conventional circuit breakers employ spring loaded latch trip
mechanisms which are manually operable to selectively open and close the circuit breaker contacts and which are automatically operable in response to overload current conditions to separate the contacts. Automatic operation occurs when a magnetic or thermal responsive sensor operates to unlatch the mechanism in response to overload currents. In the interest of effective space

utilization, the magnetic and the thermal responsive sensors are commonly interrelated.
[0005] Circuit breakers which employ the spring loaded operating
mechanism in conjunction with a releasable latch mechanism for the magnetic trip function are limited in their contact separation speed. The operating mechanism moves sequentially after release of the latch by the magnetic sensor to cause the mechanism to toggle the contacts open. Also, a time lag in the temperature sensor's response will render the static trip unit totally inoperative to initiate tripping of the circuit breaker.
[0006] Hence there is a need to provide a temperature compensation
mechanism for circuit breakers to initiate tripping of the circuit breakers automatically when the ambient temperature exceeds a safe level within the breaker enclosure.
[0007] The above mentioned shortcomings, disadvantages and
problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECT OF THE INVENTION
[0008] The primary object of the present invention is to develop an
improved mechanism for providing an auto temperature compensation for a moulded case circuit breaker.
[0009] Another object of the present invention is to develop an
improved mechanism to actuate the tripping of the thermo-magnetic release in circuit breakers.

[0010] Yet another object of the present invention is to develop an
improved mechanism to increase the range of overload and short-circuits adjustments.
[0011] Yet another object of the present invention is to develop an
improved mechanism having a temperature compensation bimetal which increases the accuracy and throughput of the circuit.
[0012] Yet another object of the present invention is to develop an
improved mechanism to reduce the time required for assembly.
[0013] 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.
D) SUMMARY OF THE INVENTION
[0014] The above mentioned shortcomings, disadvantages and
problems are addressed herein and which will be understood by reading and studying the following specification.
[0015] The various embodiments of the present invention provide an
improved auto temperature compensation for thermo-magnetic release in moulded case circuit breaker. The thermo-magnetic release system of the present invention is equipped with auto temperature compensation mechanism. The auto temperature compensation mechanism for thermo-magnetic release modules of circuit breakers comprising a main bi-metal, a temperature compensation bi-metal and a main shaft. The temperature compensation bi-metal is mounted on the main shaft. A main bimetal is

mounted on the heater The circuit assembly further includes an overload adjustment shaft, a short-circuit adjustment component, an overload adjustment component and a trip latch mechanism. Here, the temperature compensation bi-metal, the short circuit adjustment component and the overload adjustment component are mounted on the main shaft to provide a trip signal for moulded case circuit breaker to achieve temperature compensation in case of a change in ambient temperature.
[0016] According to an embodiment of the present invention, the auto
temperature compensation mechanism uses temperature compensation bimetals in addition to the main bimetal. The temperature compensation bimetals and the bimetals are of same grade or of different grades having different dimensions.
[0017] The temperature compensation bimetals are directly mounted
on the main shaft of the assembly. This in turn increases the accuracy and the throughput of the assembly. The compensation bimetals are arranged such that the overall displacement required for tripping remains same even though there is a change in ambient temperature.
[0018] According to an embodiment of the present invention, the main
bi-metal bends towards the over load adjustment shaft and makes the shaft to rotate towards the temperature compensation bi-metal. When the overload adjustment shaft touches the corresponding temperature compensation bi¬metal and rotates ftirther, the temperature compensation bi-metal which is fixed on the main shaft rotates the main shaft and pushes the latch locker vertically in an upward direction. This upward movement of the latch locker in turn unlocks the trip actuator to provide the trip signal.
[0019] The displacement required for tripping is generally maintained
constant or independent of ambient temperature by dividing the main shaft

into two parts. The temperature compensation bimetals are placed on a first shaft and the over load adjustment is provided by a second shaft. The second shaft is for instance referred as overload shaft. The linear displacement of the first shaft is halted whereas the second shaft has linear motion as well as rotation motion. The linear displacement of the second shaft provides different settings as the more linear displacement renders more number of settings whereas the rotator motion provides for the rotary motion is required for de-latching the main mechanism. The shaft is divided into two parts to achieve more linear displacement. The rotation of the second shaft also depends on the temperature compensation bi-metal. The main bimetal, the second shaft and the temperature compensation bimetal are connected in parallel to each other. The direction of bending of the bimetal and that of the temperature compensation bi-metal are in the same direction. A change in the ambient temperature causes the temperature-compensation bimetal to bend in the same direction of the main bimetal keeping the required displacement constant. The constant factor of the displacement makes the breaker independent of ambient temperature.
[0020] According to an embodiment of the present invention, the
MCCB assembly is designed for 3 pole operation. The MCCB assembly consists of a heater which is the current carrying part, a set of electromagnets and a torsion spring. The heater, the electromagnets and the torsion spring are present in three sets in the assembly. The set of electromagnets includes a fixed core and a moving core electromagnet.
[0021] Further, the assembly includes a pair of adjustment knobs, a
short circuit adjustment shaft and an overload adjustment shaft which along with the main shaft provides the trip signal for the main mechanism.
[0022] The trip de-latch mechanism consists of a trip actuator, a latch
locker, at least one compression spring and a latch spring. The trip force

produced by the thermo-magnetic release depends on the force exerted by the latch spring. The force produced by the electromagnet is used to overcome the torsion spring force and to de-latch the trip actuator. The force produced by bi-metal is used only to de-latch the trip actuator. The electromagnet is in open position and the latch mechanism is in locked position. When the short-circuit fault occurs, the moving core is attracted by the fixed core and this action makes main shaft to rotate. The latch lock which is resting on the main shaft moves vertically up which in turn de-latches the trip actuator thereby preventing any damages in the assembly.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The other objects, features and advantages will occur to those
skilled in the art fi*om the following description of the preferred embodiment and the accompanying drawings in which:
[0024] FIG.l illustrates the top view of the thermo-magnetic release
with bottom casing according to one embodiment of the present invention.
[0025] FIG.2 illustrates the side view of the thermo-magnetic release
according to one embodiment of the present invention.
[0026] FIG.3 illustrates the top view of a trip latch mechanism with
electromagnetic system in open position according to one embodiment of the present invention.
[0027] FIG.4 illustrates the trip latch mechanism with electromagnetic
system in closed position according to one embodiment of the present invention.

[0028] FIG.5 illustrates the side perspective view of a thermo-magnetic
release in a latched position according to one embodiment of the present invention.
[0029] FIG.6 illustrates the perspective view of a thermo-magnetic
release in trip position according to one embodiment of the present invention.
[0030] FIG. 7 illustrates the perspective view of a main shaft along
with the overload adjustment shaft according to one embodiment of the present invention.
[0031] FIG.8 illustrates the sectional view of a thermo-magnetic
release along with main shaft and overload adjustment shaft according to one embodiment of the present invention.
[0032] FIG.9 illustrates the perspective view of a temperature
compensation mechanism for moulded case circuit breaker according to one embodiment of the present invention.
[0033] FIG. 10 illustrates a sectional view showing the bi-metal
adjustment along with the temperature compensation a first bi-metal in deactivation state according to one embodiment of the present invention.
[0034] FIG.U illustrates a sectional view showing the bi-metal
adjustment along with the temperature compensation with a second bi-metal in deactivation state according to one embodiment of the present invention.
[0035] 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
[0036] 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.
[0037] The various embodiments of the present invention provide an
improved auto temperature compensation and trip latch mechanism for thermo-magnetic release in moulded case circuit breaker. FIG.l illustrates the top view of the thermo-magnetic release with bottom casing according to one embodiment of the present invention. The thermo-magnetic release assembly according to the present invention is designed for 3 pole operation. The assembly consists of a heater set of electromagnets and torsion spring all in three sets. The heater is the current carrying part and the electromagnets include a core and a plate.
[0038] The assembly also consists of a pair of adjustment knobs
including a short-circuit adjustment knob 11 and an overload adjustment knob 12, a short circuit adjustment component and an overload adjustment component which along with the main shaft 22 (as shown in FIG. 5) provides the trip signal for the temperature compensation mechanism. The

arrangement of bi-metal 13 on the main shaft 22 is as shown in FIG. 5. In FIG. 1, the bimetals are in normal position i.e. the bimetals are placed at normal ambient temperature and the displacement is independent of temperature. The temperature compensation bimetals 14 are directly mounted on the main shaft 22. All the components are assembled in the outer casing 15 as shown in FIG. 1. The electromagnetic system 16 is also highlighted in FIG. 1.
[0039] FIG.2 illustrates the side view of the thermo-magnetic release
module according to one embodiment of the present invention. The side view shows the overload adjustment shaft 12 mounted on the main trip shaft 22, the fixed core 26, the terminal 24, the moving core 25 connected to the short-circuit adjustment spring 23 and the short-circuit adjustment spring 23 coupled to the short-circuit adjustment shaft 21.
[0040] FIG.3 illustrates a trip latch mechanism with an outer cover and
the electromagnetic system in open position according to one embodiment of the present invention. The trip latch mechanism 31 consists of a trip actuator 32, a latch locker 37, a latch spring and one compression spring 36. The latch mechanism 31 is enlarged as shown in FIG. 3 and it consists of a compression spring 32 and a latch locker 37. The trip force produced by the thermo-magnetic release depends on the force of the compression spring 36. The moving core 33 and the fixed core 34 are connected as shown in FIG. 3. A push to trip 38 is provided to manually trip the thermo-magnetic release to trip the circuit breaker. An accessory trip 35 is also provided in the as shown in FIG. 3. The electromagnetic system shown in this FIG. 3 is in closed position.
[0041] FIG.4 illustrates the trip latch mechanism with outer cover and
electromagnetic system in closed position according to one embodiment of the present invention. The trip latch mechanism 31 consists of a trip actuator

32, a latch locker 37, a de-latch spring 41 and one compression spring 36. The latch mechanism 31 is enlarged as shown in FIG. 4 and the latch mechanism 31 consists of a compression spring 32 and a latch locker 37. The moving core 33 is coupled to the main spring 39 and the moving core 33 is in contact with fixed core 34 as shown in FIG. 4. Here the electromagnetic system is in closed position. The force produced by the electromagnet as well as bi-metals is used to de-latch the trip actuator 32 with the help of de-latching spring 41.
[0042] FIG. 5 illustrates the front side view of the thermo-magnetic
release in the latched position in accordance with one embodiment of the present invention. FIG. 6 illustrates the front side view of the thermo-magnetic release in the trip position in accordance with one embodiment of the present invention. With respect to FIG. 5 and FIG. 6, the perspective view of the thermo-magnetic release includes a latch mechanism 31 and a trip actuator 32. Further a latch locker 37 is used for locking the trip actuator 32 and the latch mechanism 31. A latch locker 37 compression spring is connected to the latch locker 37. Further an electromagnet is coimected to main shaft 22 and the springs. The electromagnet is in the open condition.
[0043] FIG. 7 illustrates a top side perspective view of the main shaft
along with the overload adjustment shaft 12 according to one embodiment of the present invention. FIG.8 illustrates a top side perspective view of the thermo magnetic release with the main shaft and the overload adjustment shaft 12 according to another embodiment of the present invention. With respect to FIG. 7 and FIG. 8 the perspective view of the thermo-magnetic release includes a main bimetal 13 and a temperature compensation bimetal 14. The main bimetal 13 and the temperature compensation bimetal 14 are interconnected through the main shaft 22. Further a constant displacement is maintained between the main bimetal 13 and the temperature compensation

bimetal 14. The constant displacement maintained between the main bimetal
13 and the temperature compensation bimetal 14 in turn bends the
temperature compensation bimetal 14.
[0044] The main shaft 22 interconnecting the main bimetal 13 and the
temperature compensation bimetal 14 also rotates in the anticlockwise direction as illustrated in shown in FIG. 8.
[0045] FIG.9 illustrates the temperature compensation mechanism for moulded case circuit breakers according to one embodiment of the present invention. To achieve auto temperature compensation, the temperature compensation bimetals 14 are used. The temperature compensation bimetals
14 and main bimetal 13 are generally of same grade but with different
dimensions. The compensation bimetals are arranged such that the overall
displacement required for tripping remains same during a a change in the
ambient temperature. The main bi-metal 13 bends towards the over load
adjustment shaft 12 and makes the shaft to rotate towards the temperature
compensation bi-metal 14. When the overload adjustment shaft 12 touches
the corresponding temperature compensation bi-metal 14 and rotates further,
the temperature compensation bi-metal 14 which is fixed on the main shaft
22 or the first shaft, rotates the main shaft 22 and pushes the latch locker 32
vertically in an upward position. The vertical movement of the latch locker
32 turn unlocks the trip actuator 37 which provides the final trip signal.
[0046] At ambient temperature both the temperature compensation
bimetal 14 and the main bi-metal 13 are in straight position. In case of an overload fault, the main bi-metal 13 bends and pushes the overload adjustment shaft 12. The main shaft in turn rotates and pushes the temperature compensation bimetal 14. The temperature compensation bimetal 14 which is firmly fixed on the main shaft 22 rotates the main shaft

22. The rotation of the main shaft 22 moves the latch locker 32, thereby releasing the latch plate.
[0047] FIG. 10 and FIG. 11 illustrates the sectional view showing the
bi-metal adjustment along the temperature compensation bimetal according to an embodiment of the present invention. The arrangement of bimetals 132, the overload adjustment shaft 12 and the temperature compensation bimetal 142 with bi-metal 1 in deactivation state is as shown in FIG. 10. An active distance adjustment slope 1001 is provided on the overload adjustment shaft 12. The main bi-metal 131 and 132 bends towards the over load adjustment shaft 12 and makes the shaft to rotate towards the temperature compensation bi-metal 141 and 142 respectively, FIG. 11 illustrates the sectional view showing the bi-metal adjustment along the temperature compensation bimetal with bi-metal 2 in deactivation state. When the overload adjustment shaft 12 touches the corresponding temperature compensation bi-metal 141 and 142 and rotates ftirther, the temperature compensation bi-metal 141 and 142 which is fixed on the main shaft 22 rotates the main shaft 22 and pushes the latch locker 32 vertically up which in turn unlocks the trip actuator 37 providing the final trip signal. The overload adjustment shaft 12 is fi-ee to rotate and fi*ee to move in an axial direction with respect to the axis of the shaft,
[0048] When there is a change in the ambient temperature, both the
temperature compensation bimetal 14 and the main bimetal 13 gets bend for a change in the ambient temperature. The bending in both the main bimetal and the compensation bimetal are equal so that the displacement between the aforementioned bimetals remains constant i.e. the rotation required for overload shaft 12 remains constant. The change in ambient temperature causes the temperature compensation bimetal to bent which in turn makes the angle of rotation required by the overload shaft to remain constant. In this case, also the overload shaft 12 pushes the temperature compensation

bimetal 14. The temperature compensation bimetal rotates the main shaft 22. The rotation of the main shaft pushes the latch locker 32 which intum releases the latch plate. This provides for ambient temperature compensation in the circuit breakers in case of higher temperature.
G) ADVANTAGES OF THE INVENTION
[0049] The auto temperature compensation bimetal of the present
invention is mounted directly on the main shaft which increases the overall throughput.
[0050] The direction of bending of the ambient compensation bimetal
and the main bimetal of the present invention is in same direction which provides the displacement to be constant. This in turn accounts for positive temperature compensation.
[0051] The Trip shaft of the present invention is divided into two parts
in axial direction which improves the overall linear displacement range. This intum increases the overload ftmctionality range of the thermo-magnetic release.
[0052] The trip latch mechanism for thermo-magnetic release of the
present invention is a standalone latch mechanism.
[0053] The number of temperature compensation bimetals used in the
present invention is equal to number of main bi-metals used per pole, for instance minimum 1 bi-metal per pole.
[0054] The trip latch mechanism of the present invention provides the
amplified tripping projections.

[0055] 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.
[0056] 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. An auto temperature compensation mechanism for thermo-magnetic
release modules of circuit breakers, the mechanism comprising;
a main bi-metal;
a temperature compensation bi-metal;
a main shaft mounted with the temperature compensation bi-metal;
an overload adjustment shaft;
a short-circuit adjustment component;
an overload adjustment component; and
a trip latch mechanism;
Wherein temperature compensation bi-metal, the short circuit adjustment
component and the overload adjustment component mounted on the main
shaft provide a trip signal for moulded case circuit breaker to achieve
temperature compensation in case of a change in ambient temperature.
2. The auto temperature compensation mechanism according to claim 1,
wherein the temperature compensation bimetals and the main bimetals are of same grade with different dimensions.
3. The auto temperature compensation mechanism according to claim 1,
wherein the temperature compensation bimetals and the main bimetals are of different grades with varying dimensions.
4. The auto temperature compensation mechanism according to claim 1,
wherein the main shaft is divided into at least two sections to mount the temperature compensation bimetals and the main bimetals so as to maintain a constant displacement required for tripping.
5. The auto temperature compensation mechanism according to claim 1,
wherein the temperature compensation bimetals and the main bimetals are arranged on either sides of the shaft such that a change in ambient temperature does not change a displacement required for tripping the circuit breaker.
6. The auto temperature compensation mechanism according to claim 1,
wherein an ambient temperature initiates the main bi-metal to bend towards the over load adjustment shaft, thereby rotating the over load adjustment shaft towards the temperature compensation bi-metal.
7. The auto temperature compensation mechanism according to claim 1,
wherein the direction of bending of the bimetal and the temperature compensation bi-metal is same.
8. The auto temperature compensation mechanism according to claim 1,
wherein the bending of temperature-compensation bimetal in the same direction of the main bimetal maintains a constant displacement thereby making the breaker independent of the ambient temperature.
9. The auto temperature compensation mechanism according to claim 1,
wherein the trip latch mechanism comprising: A trip actuator; A latch locker; and A latch spring.
10. The auto temperature compensation mechanism according to claim 12,
wherein the temperature compensation bi-metal which is fixed on the main shaft rotates the main shaft to unlock the trip actuator to provide a final trip signal.
11. The auto temperature compensation mechanism according to claim 12, wherein a rotation of the temperature compensation bimetal rotates the main shaft which pushes the latch locker which in turn releases the latch plate to provide ambient temperature compensation.