CIRCUIT BREAKER

Abstract

A circuit breaker having a mechanical switch which is inserted into a main current path and has a fixed contact and a moving contact which is connected to a contact bridge mounted movably thereto. The circuit breaker has a drive unit which is operatively connected to the contact bridge, and which comprises a first drive unit and a second drive unit. The first drive unit is energized by means of a control circuit, and the second drive unit is inserted into the main current path. Further, the invention relates to a motor vehicle.

Claims

1. A circuit breaker comprising: a mechanical switch that is inserted into a main current path and has a fixed contact and a moving contact, which is connected to a contact bridge movably mounted thereto; a drive that is operatively connected to the contact bridge and that has a first drive unit and a second drive unit, wherein the first drive unit is energized via a control circuit, and wherein the second drive unit is inserted into the main flow path.

2. The circuit breaker according to claim 1, further comprising a control unit powered from the control circuit and via which the first drive unit is energized.

3. The circuit breaker according to claim 2, wherein the control unit is signal-connected to a current sensor of the main current path.

4. The circuit breaker according to claim 1, wherein the control unit has an energy storage device for energizing the drive.

5. The circuit breaker according to claim 1, wherein the drive comprises a moving magnet actuator via which first and second drive units are formed.

6. The circuit breaker according to claim 1, wherein the drive is mechanically coupled to the contact bridge.

7. The circuit breaker according to claim 1, wherein a fuse is connected in parallel to the mechanical switch.

8. The circuit breaker according to claim 1, wherein a semiconductor switch is connected in parallel to the mechanical switch.

9. The circuit breaker according to claim 1, wherein the mechanical switch has a quenching chamber comprising a plurality of flat quenching strips arranged parallel to one another and stacked on top of one another in a stacking direction, the quenching strips being made of a ceramic.

10. A motor vehicle comprising: a high-voltage on-board electrical system; a low-voltage on-board electrical system; and a circuit breaker according to claim 1, wherein the control circuit is electrically connected to the low-voltage on-board electrical system, and wherein the high-voltage on-board electrical system comprises the main current path.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0059] FIG. 1 shows schematically a motor vehicle with a circuit breaker;

[0060] FIG. 2 is a simplified circuit diagram of the circuit breaker, which comprises a “moving magnet actuator” with two drive units; and

[0061] FIG. 3 shows schematically the “moving magnet actuator” in a sectional view;

[0062] FIG. 4 shows an example of the circuit breaker according to FIG. 2; and

[0063] FIG. 5 shows perspectively a quenching chamber of the mechanical switch.

DETAILED DESCRIPTION

[0064] In FIG. 1, a motor vehicle 2 in the form of a truck is shown in a schematically simplified view. Motor vehicle 2 has a plurality of wheels 4 by means of which contact is made with a road surface which is not shown in more detail. At least one of wheels 4 is driven by means of a main drive 6 comprising one or more electric motors. In other words, motor vehicle 2 is designed as either a hybrid motor vehicle or an electric motor vehicle.

[0065] Main drive 6 is connected to a high voltage battery 10 via a high-voltage on-board electrical system 8. High voltage battery 10 is thus used to power the high-voltage on-board electrical system 8 and to operate main drive 6. An electrical DC voltage between 400 V and 800 V is provided by high voltage battery 10, wherein the electric currents flowing between high voltage battery 10 and main drive 6 can amount to several 10 A. Further, the high-voltage on-board electrical system 8 is connected to a charging port (not shown in more detail), so that high voltage battery 10 can be charged via the charging connection and high-voltage on-board electrical system 8.

[0066] A circuit breaker 12 is inserted into high-voltage on-board electrical system 8, by means of which high-voltage on-board electrical system 8 is protected. In this case, it is possible to prevent an electric current flow between high voltage battery 10 and main drive 6 by means of circuit breaker 12. Circuit breaker 12 hereby trips in the event of a fault, so that in the event of a fault, for example, in the event of damage to main drive 6, further damage or uncontrolled behavior of main drive 6 and also a danger to occupants or passers-by are avoided. Further, circuit breaker 12 is signal-connected to an on-board computer (not shown in more detail), by means of which safe functions are carried out with the involvement of circuit breaker 12 or requests to carry out safe functions are transmitted to circuit breaker 12, which are subsequently carried out at least partially by the latter. Consequently, circuit breaker 12 also serves to provide functional safety.

[0067] Circuit breaker 12 is further electrically connected to a low-voltage on-board electrical system 14, which is powered by means of a battery 16. Battery 16 provides a DC voltage of 24 V during operation, and low-voltage on-board electrical system 14 is used to supply power to auxiliary units (not shown in more detail) which are used to operate main drive 6 and/or to provide comfort functions.

[0068] A simplified circuit diagram of circuit breaker 12 is shown in FIG. 2. Circuit breaker 12 has a main current path 18 extending between two terminals 20. The two terminals 20 are screw terminals or plug-in connections here and are placed in a housing of circuit breaker 12, which is not shown in more detail and is made of a plastic. Circuit breaker 12 further has a further main current path 22 extending between two further terminals 24, which are structurally identical to terminals 20. Main current path 18 and further main current path 22 form a part of the high-voltage on-board electrical system 8, which thus has main current path 18. For this purpose, terminals 20 and further terminals 24 are electrically contacted with suitable cables or other lines of high-voltage on-board electrical system 8.

[0069] The further main current path 22 is created simply by means of a bus bar, which is made of a metal, such as copper or brass. The further main current path 22 is connected to ground via further terminals 24, and during normal operation of motor vehicle 2, the electrical DC voltage provided by means of high voltage battery 10 is present between main current path 18 and further main current path 22. In other words, main current path 18 and further main current path 22 are assigned to different poles of high voltage battery 10.

[0070] A mechanical switch 26 is inserted into main current path 18; it thus connects the two terminals 20 and is designed as a double interrupter. For this purpose, mechanical switch 26 has a fixed contact 28 and a further fixed contact 30, each of which is rigidly connected to one of the terminals 20 by means of a rigid bus bar and are spaced apart from one another. The two fixed contacts 28, 30 are made of a material which differs from the material of the associated bus bars and which, in particular, is relatively fire-resistant.

[0071] Mechanical switch 26 further comprises a contact bridge 32 formed by means of a further bus bar which is longitudinally displaceable, therefore, movable, by means of a guide of the housing of circuit breaker 12, said guide not being shown in more detail. A moving contact 34 and a further moving contact 36 are attached, namely welded, to opposite ends of contact bridge 32, wherein the material of moving contacts 34, 36 corresponds to the material of fixed contacts 28, 30.

[0072] By displacing contact bridge 32, it is possible to bring moving contact 34 into direct mechanical contact with fixed contact 28 and further moving contact 36 into direct mechanical contact with further fixed contact 30, so that they are each electrically conductively connected. As a result, there is a low-resistance electrical connection between the two terminals 20, and mechanical switch 26 is electrically conductive. In other words, switch 26 is closed. Further, it is possible to space apart the respective contacts 28, 30, 34, 36 from one another by moving contact bridge 32. In this case, mechanical switch 26 is not electrically conductive and thus open.

[0073] Contact bridge 32 is driven by means of a drive 38, so that when drive 38 is operated, contact bridge 32 is moved and thus mechanical switch 26 is closed or opened. Consequently, drive 38 is operatively connected to contact bridge 32, namely, mechanically coupled thereto. Drive 38 has a first drive unit 39 and a second drive unit 40. Second drive unit 40 is inserted into main current path 18 between one of the terminals 20 and the further fixed contact 30. For this purpose, the bus bar is separated there, or second drive unit 40 is partially formed by means of the bus bar. Thus, when electrical current flows through main current path 18, second drive unit 40 is also always energized.

[0074] First drive unit 39 is energized by a control unit 41, which is connected electrically to drive 38, namely, first drive unit 39, for this purpose. For energizing control unit 41 and consequently first drive unit 39, control unit 41 is electrically contacted with a control circuit 42, by means of which a DC voltage is provided. Control circuit 42 is in direct electrical contact with the low-voltage on-board electrical system 14, so that the DC voltage of 24 V is also conducted by means of control circuit 42. In summary, first drive unit 39 is thus energized by means of control circuit 42.

[0075] Control unit 41 includes an energy storage device 44 in the form of a capacitor, which is charged via control circuit 42, and which is electrically connected in parallel to a microcontroller of control unit 41. Thus, by means of energy storage device 44, fluctuations in the electrical voltage and/or the electric current of the low-voltage on-board electrical system 14 are intercepted, so that damage to the microcontroller is avoided hereby. Also, because of energy storage device 44, it is possible to actuated drive 38 at least once in the event of a failure of the low-voltage on-board electrical system 14 and to open switch 26 in this way.

[0076] In a variant shown in more detail, control unit 41 also has a charge pump by means of which it is possible to increase the electrical voltage applied to capacitor 44 compared to the electrical voltage provided by means of low-voltage on-board electrical system 14, so that the amount of energy stored by means of energy storage device 44 is increased. Thus, a safe operation of drive 38 is always possible, even if there is a complete failure of low-voltage on-board electrical system 14 or if drive 38 is slightly blocked.

[0077] The energizing of first drive unit 39 is set by means of the microcontroller, and it is signal-connected to a current sensor 46 of main current path 18. Current sensor 46 is inserted into main current path 18 and is configured as a shunt that is electrically connected in series to second drive unit 40. Thus, measuring the electric current carried by main current path 18 is enabled by current sensor 46. Further, circuit breaker 12 has a first voltage sensor 48 by means of which the electrical voltage present between one of the terminals 20 and one of the other terminals 24 can be measured. The electrical voltage present between the remaining terminal 20 and the remaining further terminal 24 can be measured by means of a second voltage sensor 50. The electrical voltage dropping across the series connection comprising current sensor 46 and second drive unit 40 is measurable by means of a third voltage sensor 52, and the electrical voltage dropping across the series connection comprising current sensor 46, second drive unit 40, and mechanical switch 26 is measurable by means of a fourth voltage sensor 54. All voltage sensors 48, 50, 52, 54 are signal-connected to control unit 40, namely, the microcontroller.

[0078] During operation, the microcontroller of control unit 41 checks the change over time of the electrical voltages measured by means of voltage sensors 48, 50 52, 54 and the electric current measured by means of current sensor 46. If the change over time of the measured current corresponds to an increase and exceeds a certain limit value, drive 38, namely, first drive unit 39, is activated by means of control unit 41 so that switch 26 is opened. The limit value is selected such that it is only exceeded in the event of a fault, namely, in the case of an electrical short circuit of the electric motor of main drive 6. Due to the actuation of mechanical switch 26, the electric current is interrupted and thus further destruction of the electric motor or further components of main drive 6 is avoided.

[0079] In addition, second drive unit 40 is designed such that no force or only a small force is exerted by means of it in normal operation, therefore, when the electric current conducted by means of main current path 18 corresponds to the target value and/or, in particular, is less than or equal to a nominal value, so that contact bridge 32 is not moved. However, if the electric current carried by means of main current path 18 exceeds a further limit value or the limit value, the force, in particular the sufficiently large force, exerted by means of second drive unit 40 is such that contact bridge 32 is moved and mechanical switch 26 is opened. Consequently, second drive unit 40 acts to assist first drive unit 39 in the event of an excessive increase in the electric current through main current path 18. In addition, this ensures that even if control unit 41 or first drive unit 39 fails, mechanical switch 26 is reliably opened in the event of a fault.

[0080] Similarly, actuation of mechanical switch 26 by means of control unit 41 occurs when the electrical voltage detected by means of voltage sensors 48, 50, 52, 54 is used to conclude that a fault has occurred, such as a malfunction of certain components of motor vehicle 2. This can also be a malfunction of second drive unit 40, so that it is no longer or only partially ready for operation. In this case as well, first drive unit 39 is energized by means of control unit 41 so that switch 26 is opened, therefore, if this is not possible by means of second drive unit 40, or if the fault does not lead to an actuation of second drive unit 40.

[0081] If mechanical switch 26 is opened and the fault exists, a relatively high electrical voltage is present between terminals 20 during the opening of switch 26. As a result, an arc is formed in each case between fixed contacts 28, 30 and the associated moving contact 34, 36, each of which is moving away, and current continues to flow across the arc. However, the electrical voltage dropping across mechanical switch 26 increases. As a result, electric current commutates from electrical switch 26 to a fuse 56 connected in parallel therewith. Thus, the electric current between the two terminals 20 flows through fuse 56, which is why the arcs are quenched.

[0082] Fuse 56 is dimensioned to trip in the event of a fault. The threshold at which fuse 56 is tripped is between the value of the electric current in normal operation and the value of the electric current resulting from a short circuit, wherein the exact value of the threshold in between can be chosen arbitrarily without changing the functioning of circuit breaker 12. Thus, the error tolerances for fuse 56 can be selected to be relatively large, which is why manufacturing costs are reduced. After fuse 56 has been tripped, it can also no longer conduct electric current , and the two terminals 20 are galvanically isolated from one another.

[0083] In FIG. 3, drive 38 is shown schematically in a sectional view along an axis 58. Drive 38 is configured as a “moving magnet actuator” and thus has two disc coil or drum type holders 60, which are concentric with and spaced along axis 58 and which are made from a ferromagnetic material. Positioned between these is an annular short-circuit plate 62 which is concentric with axis 58 and is also made from a ferromagnetic material. By means of holders 60 and short-circuit plate 62, a hollow cylinder is thus formed, within which a further holder 64 made of a plastic is arranged and is mounted so as to be displaceable along axis 58 by means of a guide which is not shown in more detail. Attached to holder 64 is a rod 66 which extends along axis 58 and is attached to contact bridge 32, either directly or via a mechanism not shown in more detail. Embedded in the cylinder-like further holder 64 is a cylinder-shaped permanent magnet 68 having two magnetic poles 70, each of which forms one of the ends of permanent magnet 68 in a direction parallel to axis 58.

[0084] First drive unit 39 of drive 38 comprises two electric coils 74. Each of the electric coils 74, which are structurally identical to one another, is wound on one of the holders 60, and these are electrically connected in parallel to one another. Second drive unit 40 has two further electric coils 78, one of which is wound on one of the electric coils 74 and the other of which is wound on the remaining electric coil 74. The two further electric coils 78 are also connected electrically in parallel to one another. The number of turns of the further electric coils 78 is less than the number of turns of electric coils 74, and each of the further electric coils 78 preferably has at most 10 turns.

[0085] If the two drive units 39, 40 are not energized, the magnetic interaction with short-circuit plate 62 as well as holders 60 pulls permanent magnet 68 into a position substantially within short-circuit plate 62, wherein a force of approximately 30 N acts on the permanent magnet 68 and thus also on further holder 64. Short-circuit bridge 32 is thus also held in the desired position with this force, namely, in the position in which mechanical switch 26 is closed.

[0086] If an electric current flows via main current path 18, second drive unit 40 is energized so that a magnetic field, which interacts with the magnetic field of permanent magnet 68, is created by means of further electric coils 78. However, the interaction is small due to the small number of turns of the further electric coils 78 when the rated current is conducted by means of main current path 18, and the force acting on permanent magnet 68 is less than 30 N, so that the position of permanent magnet 68 is not changed.

[0087] In the event of a fault, first drive unit 39 is energized by means of control unit 41, so that a magnetic field is also created in each case by means of electric coils 74. Also, the strength of the magnetic fields created by means of the further electric coils 78 is increased. As a result, permanent magnet 68 is pushed away from one of the holders 60 along axis 58 and pulled toward the remaining holder 60. In so doing, relatively large forces act on permanent magnet 68 and consequently also on contact bridge 32 via the further holder 64 and rod 66, so that mechanical switch 26 is opened relatively quickly.

[0088] If the fault is not present and, for example, only the energizing of main drive 6 is to be interrupted, for example, for maintenance, only first drive unit 39 is energized by means of control unit 41, wherein switch 26 is opened relatively slowly. As a result, an electrical load and also a mechanical load on circuit breaker 12 are reduced. In this case, because the applied electrical voltage between terminals 20 is limited, fuse 56 does not trip and circuit breaker 12 can be returned to the electrically conductive state, for example, after maintenance has ended. For this purpose, for example, first drive unit 39 is energized in the opposite direction or the energizing is terminated so that permanent magnet 68 is again pulled to short-circuit plate 62.

[0089] In a variant not shown in more detail, second drive unit 40 comprises a plurality of diodes by means of which it is ensured that the current flow direction through the further electric coils 78 is always the same, irrespective of the current flow direction of main current path 18. It is thus possible to operate circuit breaker 12 in a bidirectional manner.

[0090] An alternative embodiment of circuit breaker 12 is shown schematically simplified in FIG. 4, wherein some components, such as main current path 22 and voltage sensors 48, 50, 52, 54, are not shown. However, these are also present but can also be omitted, as is also the case with the previous embodiment. Drive 38 with the two drive units 39, 40 and mechanical switch 26 are not modified.

[0091] However, fuse 56 is replaced by a switch group 80, by means of which mechanical switch 26 is thus bridged. Switch group 80 comprises two semiconductor switches 82 that are anti-serially connected to one another. Consequently, the two semiconductor switches 82 are connected in parallel to mechanical switch 26. The two semiconductor switches 82 are operated by means of a further control unit 84 and are placed by means of the latter into either the electrically conductive or electrically nonconductive state. Energizing of the further control unit 84 occurs by means of a further voltage supply 86, which is powered either by means of an electrical voltage dropping across mechanical switch 26 or by means of control circuit 42.

[0092] A surge protector 88, which in the illustrated variant is a varistor, is connected in parallel to switch group 80. In a variant not shown in more detail, surge protector 88 is realized using Zener diodes, TVS diodes, an RCD circuit, a controllable resistive load, or a combination thereof. By means of surge protector 88, an electrical overvoltage at switch group 80 as well as the further control unit 84 and the further voltage supply 86 is avoided, which could otherwise lead to destruction thereof. Further, another current sensor 90 and another fuse 92 are electrically connected in series between main current path 18 and switch group 80.

[0093] In this embodiment of circuit breaker 12, semiconductor switches 82 are electrically nonconductive as long as mechanical switch 26 is closed. When switch 26 is opened, the electrical voltage across switch assembly 80 increases so that the further voltage supply 86 is operated and therefore the further control unit 84 is energized. Switch group 80, namely, the individual semiconductor switches 82, is activated by means of further control unit 84, so that they become current-carrying. As a result, the electric current commutates and is conducted by means of switch group 80. Therefore, the arcs formed between fixed contacts 28, 30 and the respective moving contacts 34, 36 are quenched. Subsequently, semiconductor switches 82 are electrically controlled in such a way that they electrically block, so that the electric current flow between the two terminals 20 is terminated.

[0094] It is ensured until then by means of surge protector 88 that no overload of semiconductor switches 82 occurs. If it is detected by means of the further current sensor 90, which is signal-connected to the further control unit 84, that a relatively large electric current is carried by switch group 80, which could lead to damage of semiconductor switches 82, semiconductor switches 82 are also opened and thus damage to switch group 80 is avoided. It is thereby ensured by means of the further fuse 92 that even in the event of a malfunction of the further control unit 84 as well as in the event of a relatively high electric current, the current flow across switch group 80 is interrupted.

[0095] A perspective view of a quenching chamber 94 of mechanical switch 26 is shown in FIG. 5. Quenching chamber 94 is used hereby to quench an arc generated during a switching operation of mechanical switch 26, unless the other components present are used for this purpose. Quenching chamber 94 has a plurality of quenching strips 98 stacked on top of another in a stacking direction 96. Quenching strips 98 are made of an aluminum oxide ceramic and are designed flat and arranged perpendicular to stacking direction 96. The thickness of quenching strips 98, therefore, their extent in the stacking direction 96, is between 1 mm and 2 mm. Quenching strips 98 are directly adjacent to one another so that a stack 100 is formed. In this regard, stack 100 has a plurality of layers 102 arranged one on top of another in the stacking direction 96, which are thus arranged perpendicular to the stacking direction 96.

[0096] Two of quenching strips 98 are associated with each of the layers 102. The two quenching strips 98 of each layer 102 are hereby different from one another, and one of quenching strips 98 is formed wedge-shaped and the remaining one is trapezoidal. In other words, quenching strips 98 associated with each of the layers 102 differ, wherein, however, the same quenching strips 98, therefore, of the same type, are associated with each layer 102. In other words, quenching chamber 94 has two different types of quenching strips 98, namely, the wedge-shaped and the trapezoidal ones, and these are evenly distributed among layers 102.

[0097] The two quenching strips 98 of each layer 102 are spaced apart from one another perpendicular to stacking direction 96 so that a slot 104 is formed between them. Four of the layers 102 in each case are combined into a group 106, wherein quenching strips 98 of each group 106 are arranged flush with one another. Quenching strips 98 of the respective adjacent group 106, in contrast, are arranged in a mirror-inverted manner, so that stack 100 has a plurality of chambers 108 which lie one above the other in the stacking direction 96 and are separated from one another and each of which is formed by means of the mutually aligned slots 104. Due to the wedge or trapezoidal shape, a notch 110 is formed in each of the layers 102 and merges into the respective chambers 108. There are four such groups 106 in all.

[0098] Stack 100 is encompassed on both sides by a holder 112 in each case and is thus stabilized. Holders 112 are mirror images of each other and are made of a plastic material, and each has a base 114. The two holders 112 are attached to one another at the respective base 114, so that stack 100 is frictionally held between the two holders 112 both in the stacking direction 96 and perpendicular thereto. On the side opposite stack 100, each of the holders 112 has a rectangular pot- or pan-shaped receptacle 116 within each of which, in the assembled state, a permanent magnet 118 lies, each of which forms a driving element.

[0099] Quenching chamber 94 is oriented with respect to fixed contact 28, 30 as well as to moving contact 34, 36 such that an arc generated when mechanical switch 26 is actuated, therefore, when drive 38 is actuated, strikes stack 100 in the region of notches 110. Due to the interaction between the magnetic field of permanent magnets 118 and the magnetic field created by the arc, the arc is driven further into stack 100, namely, into the individual chambers 108. Thus, subsections of the arc are formed in the respective chambers 108, said subsections being U-shaped. The subsections are connected to one another, wherein the connecting sections encompass stack 100 on the side of notches 110. Consequently, the arc has a relatively long length. Due to notches 110, it is not possible for the arc to bypass quenching chamber 94. Due to the increase in the length of the arc, an electrical voltage required to sustain it increases.

[0100] Further, heat input from the plasma forming the arc into the individual quenching strips 98 occurs, so that the arc is cooled. Due to the ceramic used, the heat is dissipated relatively effectively and the arc is thus cooled. Because of the cooling, the electrical voltage required to maintain the arc also increases. Because the individual quenching strips 98 are separate from one another, no excessive mechanical stress is formed in stack 100 hereby, even if the individual quenching strips 98 are heated unevenly, which could lead to destruction.

[0101] The invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can also be derived herefrom by the skilled artisan, without going beyond the subject of the invention. Particularly, further all individual features described in relation to the individual exemplary embodiments can also be combined with one another in a different manner, without going beyond the subject of the invention.

[0102] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.