Title of Invention

A DEVICE FOR PREVENTING DOWNRATING OF A CIRCUIT BREAKER FOLLOWING OF AN ADD ON AUXILIARY

Abstract

The present invention relates to a device for preventing downrsting of a circuit breaker following fitting of an add-on auxiliary such as in particular a differentiat protection device, said device comprising the circuit breaker and the auxiliary, said circuit breaker being provided with at least one adjusting screw arranged to perform an initial setting of a thermal trip device corresponding to the rating of the circuit breaker, wherein it comprises means for a new automatic setting of the thermal trip device when the add¬on auxiliary is fitted, said means comprising at least one actuator securedly united to the auxiliary for performing said new setting of the thermal trip device by acting on a receiver part securedly united to the circuit breaker. PRICE: THIRTY RUPEES

Full Text

The present invention relates to a device for anti-downrating of a circuit breaker following fitting of an auxiliary unit such as notably a differential protection device, this circuit breaker being provided with at least one adjustment screw arranged to perform an initial adjustment of a thermal trip device and to define the thermal protection of the circuit breaker corresponding to its rating. In a circuit breaker, the thermal protection against overloads is set in the factory taking account of the heat rises of the cables and of the heat dissipation of the equipment itself. This heat dissipation by Joule effect is due to the internal resistances and is removed by the external faces in contact with the ambient air as well as by the power supply cables. When an auxiliary unit is fitted, such as a differential protection device for example, the balance of the circuit breaker heat exchanges is modified notably due to the reduction of the heat exchange surfaces with the ambient air, to the local modification on output and through the auxiliary unit of the cross-sections of the conductors, to the heat dissipation proper to the auxiliary unit and to the limitation of the heat removal by the power supply cables. On account of these modifications to the thermal balance, the circuit breaker trips earlier on overload and normally has to be downrated to continue providing the scheduled protection. Various solutions enable this phenomenon to be attenuated, for example increasing the cross-sections of the auxiliary unit conductors, providing ventilation apertures, or fitting thermal shields. These solutions are not however completely satisfactory, notably on high-rating equipment. The present invention proposes to solve this problem in a simple and efficient manner, either automatically or manually. For this purpose, the anti-downrating device according to the invention is characterized in that it comprises means arranged to perform a new adjustment of the thermal trip device setting when the auxiliary unit is fitted. According to a first embodiment, said means arranged to perform the new setting adjusting of the thermal trip device are manual. In this case, they preferably comprise a thermal setting knob fitted on each pole of the circuit breaker. According to a second embodiment, said means arranged to perform the new setting adjustment of the thermal trip device are automatic. In this case, they preferably comprise at least one actuator securedly united to the auxiliary unit and arranged to act on an adjustment bar of the thermal trip device of the circuit breaker. Accordingly the present invention provides a device for preventing dovvnrating of a circuit breaker following fitting of an add-on auxiliary such as in particular a differential protection device, said device comprising the circuit breaker and the auxiliary, said circuit breaker being provided with at least one adjusting screw arranged to perform an initial setting of a thermal trio device corresflomdins to the ratina of the circuit breaker, wherein it comprises means for a new automatic setting of the thermal trip device when the add-on auxiliary is fitted, said means comprising at least one actuator securedly united to the auxiliary for performing said new setting of the thermal trip device by acting on a receiver part securedly united to the circuit breaker. The present invention and its main advantages will become more clearly apparent with reference to the description of a preferred embodiment and to the accompanying drawings given as non-restrictive examples only in which; Figure 1 is a schematic view illustrating the side faces of a circuit breaker and of an auxiliary equipped with the device according to the invention, Figure 2 represents a schematic view of a first embodiment of the device according to the invention. Figure 3 represents a schematic view of a second embodiment of the device according to the invention, Figure 4 represents a detailed view illustrating a first embodiment of the device of the invention. Figure 5 represents a detailed view illustrating a second embodiment of the device of the invention, Figure 6 is a schematic view illustrating a circuit breaker associated to two auxiliary units. Figures 7A and 7B represent a conventional circuit breaker equipped with adjustment screws of the thermal trip device, Figures 8A and 8B illustrate the foregoing circuit breaker equipped with thermal setting knobs and the knobs which constitute the device according to the invention in a first position prior to fitting of the auxiliary unit, and Figures 9A and 9B illustrate the foregoing circuit breaker equipped with thermal setting knobs and the knobs which constitute the device according to the invention in a second position subsequent to fitting of the auxiliary unit. With reference to figure 1, an auxiliary unit 10 such as for example a differential protection device, seen from the side, is designed to be fitted to a circuit breaker 11 also represented seen from the side. The auxiliary unit is equipped with an actuator 12 arranged to act automatically on a receiver part 13, this receiver part being designed to automatically perform a new setting of the thermal trip device on each of the poles of the circuit breaker, when the auxiliary unit is fitted to the circuit breaker. The actuator 12 is formed by a protuberance apparent on one side face of the auxiliary unit and the receiver part 13 is formed by a thermal device adjustment bar, the end of this bar being located facing a window 14 arranged in a side face of the circuit breaker, in correspondence with said protuberance constituting the actuator 12. Figure 2 illustrates, in sectional view, a multipole circuit breaker 11 designed to receive an auxiliary unit 10 equipped with an actuator 12. The electrical coupling is performed by-means of conductors 15 which extend laterally at the base of the auxiliary unit and which present branches with elbow bends enabling connection to the circuit breaker poles. The thermal trip device 16 comprises bimetal strips 16a, 16b, 16c and 16d respectively associated to each of the circuit breaker poles. The receiver part 13 is formed by an adjustment bar 17 with two levels defined by the presence of bosses 17a, 17b, 17c and 17d having a cam function to act on the position of the bimetal strips 16a, 16b, 16c and 16d. In the initial state corresponding to use of the circuit breaker without an auxiliary unit, the bimetal strips occupy a first position, called the low position. In the final state, corresponding to use of the circuit breaker after fitting of an auxiliary unit, the bimetal strips occupy a second position, called the high position, defined by the bosses 17a, 17b, 17c and 17d. This second position takes account of the new distribution of the heat exchanges due to the addition of the auxiliary unit. It is obtained by movement of the adjustment bar 17 in the direction of the arrow A, brought about by the thrust exerted by the actuator 12 which engages in a window 14 identical to the one defined with reference to figure 1 and bears on the end of this bar. This bar moreover comprises a bearing stop 18 of a return spring 19. When movement of the adjustment bar from the first to the second position takes place, the spring is coitpressed. If the auxiliary unit is removed, the adjustment bar can revert to its initial position due to the action of the return spring 19. In this case, the bimetal strips return to their position called the low position. In this embodiment, all the bosses 17a, 17b, 17c and 17d have the same dimensions and notably the same height. The new adjustment of the bimetal strips when an auxiliary unit is added is therefore the same for all the poles of the circuit breaker. It is admitted in this case that the incidence of adding an auxiliary unit is the same for all the poles. In practice, the balance of the heat exchanges due to the addition of an auxiliary unit is different from one pole to the other. In fact, if the auxiliary unit is fitted on one side of the differential, the closest pole is the most disturbed. The disturbance is attenuated the further the poles are situated from the wall of the circuit breaker adjoined to the auxiliary unit. A previous alternative embodiment, illustrated by figure 3, takes this fact into account. The adjustment bar 27 comprises in this case bosses 27a, 27b, 27c and 27d which have an increasing height from left to right in the figure. In this way, the new adjustment of the bimetal strips 16a, 16b, 16c and 16d is performed according to the distance at which they are located from the face of the circuit breaker 11 adjacent to the auxiliary unit 10. As previously, the auxiliary unit is provided with an actuator 12 which engages in a window 14 arranged in the side panel of the circuit breaker, facing the end of the adjustment bar 27. By this embodiment, a progressive staging of the new adjustment of the bimetal strips is achieved." The action of the adjustment bar on the bimetal strips can be performed in different manners. Figure 4 illustrates an embodiment according to which it acts on the base or foot of the bimetal strips. A bimetal strip 30 is mounted on a base 31 which comprises a U-shaped element 32 one of whose branches 32a bears an adjustment screw 33 and whose other branch 32b is linked to the straight active blade 34 of the bimetal strip. The central part of the U-shaped element 32 is mounted on a support 35 pivoting on a fixed spindle 3 6 securedly united to the circuit breaker. A branch 37, securedly united to this support, is on the one hand pressing on the adjustment bar 38 and on the other hand pushed against this bar by a spiral spring 39. The initial adjustment of the setting of the bimetal strip is performed by means of the adjustment screw 33 which is engaged in two nuts 40 and 41 located on each side of the branch 32a of the U-shaped element 32. The end of this screw bears against the other branch 32b of this element. Setting consists in moving the two branches apart in a suitable manner. It enables the distance x between the end of the active blade 34 and a trip rod 42 in case of overheating to be adjusted. The action of the adjustment bar 38 consists in acting on the initial separation distance x by making the base of the bimetal strip pivot on the spindle 36. Figure 5 illustrates another operating mode according to which the bar acts directly on a trip rod 50 in case of overheating and no longer on the bimetal strip. In this construction, the active blade 51 of the bimetal strip is securedly united to a bent base 52. An adjustment screw 53 enables the initial distance x2 separating the end of the active blade from the rod 50 to be adjusted, by modifying the angle of the elbow bend formed by the bent base 52 one of whose branches is securedly united to the circuit breaker case and whose other branch is free. The adjustment bar 54 acts on the position of the rod 50. If no auxiliary unit is fitted, this rod occupies a position represented in unbroken lines, and the distance separating the active blade from the rod is x2. When an auxiliary unit is fitted, the adjustment bar is pushed and a boss 55, identical to those described with reference to figures 2 and 3, has the effect of moving the rod 50 to a position represented in broken lines. In this position, the distance separating this rod from the active blade is modified and has the value xl. Figure 6 illustrates an embodiment wherein the circuit breaker 11 can be associated to two auxiliary units 10a and 10b which both comprise an actuator, respectively 12a and 12b. In such a construction, the circuit breaker must comprise two adjustment bars whose effects are combined to perform a new setting of the bimetal strips taking account of the new thermal dissipation balance conditions due to the addition of the auxiliary units. All these embodiments correspond to a new setting of the bimetal strips which is performed automatically at the time when an operator associates to the circuit breaker one or two auxiliary units fitted onto the side faces of this circuit breaker. This automatic adjustment is due to the interaction of the trip device or devices on the adjustment bar or bars. Other embodiments enable the same effect to be obtained manually. Different embodiments are provided for this purpose. As is shown by figures 7A and 7B, a two-pole circuit breaker 60 is equipped, in a manner known as such, with adjustment screws 61. Setting can be performed in the factory or at the end of production, or at the grouping and delivery centre, or at the official distributor's according to the rules which are known and supplied by the manufacturer. The action of the screw is exerted mainly, but not only, on the base or foot of the bimetal strip. The adjustment screw is of the sunken head type and comprises a cavity 62 arranged to receive a manual thermal calibration knob 63 represented by figures 8A and 8B. The knob 63 is provided with a protuberance 64 having a grooved surface which corresponds in size and in shape to the cavity 62 of the adjustment screw 61, in such a way that this knob can be fitted onto this adjustment screw. The front part 65 of the knob comprises an indicator mark, for example an arrow 66 (see figure 8A), which occupies an initial position, such as for example represented by figure 8A if no auxiliary unit is fitted and a final position obtained for example by rotation of the knob a quarter of a turn, as shown in figure 9A, when an auxiliary unit 67 has been fitted to the circuit breaker 60. For the purposes of making the assembly tamperproof, a card 68, represented in broken lines, can be fitted over the thermal setting knob to mask it completely and prevent unauthorised use of this knob. This cache is fitted at the end of the cavity arranged in each pole of the circuit breaker and which enables access to the adjustment screw 61 and to the thermal setting knob 63. It is obvious that this thermal setting knob could be dissociated from the adjustment screw. In this case, it acts on the bimetal strip in a zone different from the deformation zone on which the adjustment screw acts. For example, if the adjustment screw acts on the foot of the bimetal strip, the setting knob can act either on its straight active branch or on a trip rod such as described with reference to figure 5, whose position is modified by means of said knob. WE CLAIM: 1. A device for preventing downrating of a circuit breaker following j5tting of an add-on auxiliary such as in particular a differential protection device, said device comprising the circuit breaker and the auxiliary, said circuit breaker being provided with at least one adjusting screw arranged to perform an initial setting of a thermal trip device corresponding to the rating of the circuit breaker, wherein it comprises means for a new automatic setting of the thermal trip device when the add-on auxiliary (10,67) is fitted, said means comprising at least one actuator (12, 12a, 12b) securedly united to the auxiliary for performing said new setting of the thermal trip device by acting on a receiver part (13) securedly united to the circuit breaker. 2. The device according to claim 1, wherein said actuator is arranged to act on a bimetal strip for each pole-unit of the circuit breaker (60). 3. The device according to claim 1, wherein said actuator arranged to act on a rod of a trip mechanism associated to a bimetal strip for each pole-unit of the circuit breaker (60). 4. The device according to claim 1, wherein said actuator (12,12a, 12b) is formed by a protuberance apparent on a side wall of the auxiliary. 5. The device according to claim 1, wherein said receiver part (13) is formed by an adjusting bar (17) of the thermal trip device, one end of which is located facing a window (14) arranged in a side panel of the circuit breaker in correspondence with said actuator. 6. The device according to claim 5, wherein said adjusting bar (17) comprises bosses (17a, 17b, 17c, 17d; 27a, 27b, 27c, 27d) co-operating in the manner of cams on the position of a component of the thermal trip device corresponding to each pole-unit of the circuit breaker. 7. The device according to claim 6, wherein the bosses (17a, 17b, 17c, 17d; 27a, 27b, 27c, 27d) of the adjusting bar (17) are arranged to act respectively on bimetal strips (16a, 16b, 16c, 16d) of the thermal trip device of each pole-unit of the circuit breaker. 8. The device according to claim 6, wherein the bosses (17a, 17b, 17c, 17d; 27a, 27b, 27c, 27d) of the adjusting bar (17) arranged to act respectively on a rod (42, 50) of a tripping mechanism associated to a bimetal strip for each pole-unit of the circuit breaker. 9. The device according to claim 6, wherein said bosses (17a, 17b, 17c, 17d) are of equal height. 10. The device according to claim 6, wherein said (27a, 27b, 27c, 27d) are of different height. 11. A device for preventing downrating of a circuit breaker substantially as herein above described with reference to the accompanying drawings.

Documents:

1492-mas-1995 abstract.jpg

1492-mas-1995 abstract.pdf

1492-mas-1995 claims.pdf

1492-mas-1995 correspondence others.pdf

1492-mas-1995 correspondence po.pdf

1492-mas-1995 description (complete).pdf

1492-mas-1995 drawings.pdf

1492-mas-1995 form-1.pdf

1492-mas-1995 form-26.pdf

1492-mas-1995 form-4.pdf

1492-mas-1995 form-9.pdf

1492-mas-1995 petition.pdf