GB2593932A

GB2593932A - Commutating electric circuit breaker with reliable actuating mechanism and operation method thereto

Info

Publication number: GB2593932A
Application number: GB2005348.4A
Authority: GB
Inventors: Kopejtko Petr
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2020-04-10
Filing date: 2020-04-10
Publication date: 2021-10-13
Also published as: WO2021204992A1; GB202005348D0

Abstract

A circuit breaker 1a comprises a frame 2 to which is fixed two fixed main contacts 3a,b and at least three fixed arcing contacts 4a,b,c. A first electrical terminal 5a is electrically connected to one of the fixed main contacts and a first of the fixed arcing contacts. A second electrical terminal 5b is electrically connected to the other fixed main contact and a second of the fixed arcing contacts. A movable contact piece 8a carries a movable main contact 9 and movable arcing contacts 10a,b, wherein the number of movable arcing contacts equals the number of fixed arcing contacts minus one. An actuator 13a moves the contact piece from an ON-position P1 (in which the movable main contact is in contact with the fixed main contact) via a COMMUTATING-position P3 (in which the movable main contact is separated from the fixed main contacts and each movable arcing contact is in contact with a different pair of the fixed arcing contacts) to an OFF-position P7 (in which the movable main contact is separated from the fixed main contacts and all movable arcing contacts are separated from the fixed arcing contacts). All movable arcing contacts may be separated from the fixed arcing contacts in the ON-position.

Description

Commutating electric circuit breaker with reliable actuating mechanism and operation method thereto

TECHNICAL FIELD

The invention relates to an electric circuit breaker, which comprises a frame, two static main contacts fixedly arranged in or on the frame and a movable main contact, by which the electric circuit breaker can be switched ON and OFF. Moreover, the electric circuit breaker comprises static and movable arcing contacts, to which a current commutates from the main contacts during switch off. Furthermore, the invention relates to an operation method for such an electric circuit breaker.

BACKGROUND ART

An electric circuit breaker and an operating method thereto generally is known in prior art. For example, EP 3 410 454 Al and WO 2015/091844 Al disclose circuit breakers with a current commutation function.

A drawback of the known circuit breakers is that a control mechanism to control the contacts is technically complicated and thus vulnerable to failure.

DISCLOSURE OF INVENTION

Accordingly, an object of the invention is the provision of an improved electric circuit breaker and an improved operating method thereto. In particular, the actuating mechanism for controlling the contacts shall be less technically complicated and thus less vulnerable to failure.

The object of the invention is solved by an electric circuit breaker, which comprises a frame, two static main contacts fixedly arranged in or on the frame, at least three static arcing contacts fixedly arranged in or on the frame at a distance from the static main contacts, a first electrical terminal arranged in or on the frame, which is electrically connected to a first of the static main contacts and a first of said at least three static arcing contacts, a second electrical terminal arranged in or on the frame, which is electrically -2 -connected to a second of the static main contacts and a second of said at least three static arcing contacts, wherein the first and the second electrical terminal are provided for switching the electric circuit breaker in a current path of an electric circuit, a contact piece which is movably supported in the frame in relation to the static main contacts and the static arcing contacts, a movable main contact fixedly arranged on the movable contact piece, movable arcing contacts fixedly arranged on the movable contact piece at a distance from the movable main contact and electrically insulated thereof, wherein the count of the movable arcing contacts equals the count of the static arcing contacts minus one and an actuator, which is designed to move the contact piece from an ON-position to an OFF-position via a COMMUTATING-position, wherein the movable main contact is in contact with the two static main contacts in the ON-position, wherein the movable main contact is displaced from the two static main contacts in the COMMUTATING-position and wherein each movable arcing contact of the at least two movable arcing contacts is in contact with a different pair of the at least three static arcing contacts in the COMMUTATING-position and wherein the movable main contact is displaced from the two static main contacts in the OFF-position and wherein all movable arcing contacts are displaced from the at least three static arcing contacts in the OFF-position, too.

The object of the invention furthermore is solved by a method of switching OFF an electric circuit breaker of the above kind, wherein the movable main contact is in contact with the two static main contacts in the ON-position, wherein each movable arcing contact of the at least two movable arcing contacts gets in contact with a different pair of the at least three static arcing contacts before the movable main contact gets displaced from the two static main contacts between the ON-position and the COMMUTATING-position, wherein the movable main contact is displaced from the two static main contacts in the COMMUTATING-position and wherein each movable arcing contact of the at least two movable arcing contacts is in contact with a different pair of the at -3 -least three static arcing contacts in the COMMUTATING-position and wherein all movable arcing contacts get displaced from the at least three static arcing contacts between the COMMUTATING-position and the OFF-position and wherein the movable main contact is displaced from the two static main contacts in the OFF-position and wherein all movable arcing contacts are displaced from the at least three static arcing contacts in the OFF-position, too.

Advantageously, the number of arcs or air gaps is increased with the number of movable arcing contacts and static arcing contacts in relation to a single main switching contact. In turn, the voltage of each switching arc is reduced what helps in quickly cutting off a current drawn by the electric circuit breaker. In detail, the number of arcs or air gaps equals twice the number movable arcing contacts. Any desired number of movable arcing contacts and static arcing contacts may be chosen in accordance with the voltage, which is to be switched off, and in accordance with the travel distance of the movable contact piece from an ARCING-position, where arcing starts, to the position where the arcs are actually quenched.

A further advantage of the proposed solution is that the movable main contact and the two static main contacts are not deteriorated much by arcing so that a low contact resistance can be guaranteed over a long period of time.

The proposed electric circuit breaker is particularly usable in DC applications, but it may also used in AC applications or mixed DC/AC applications.

It should be noted that "fixedly arranged" does not necessarily mean "non-removable". Instead "fixedly arranged" in the given context mainly is related to static contacts and mainly meant as an opposite to movable contacts.

It should also be noted that the frame can be arranged within a housing of the electric circuit breaker, can be an integral part of a housing of the electric circuit breaker or can form a housing of the electric circuit breaker as such.

The ON-position is the position of the contact piece, in which the movable main contact is aligned with the static main contacts. In this position, the ohmic resistance in the main branch, in which the movable main contact and the static main contacts are located then, reaches its minimum. In particular, the ON-position is the position, -4 -where a movement of the contact piece finally stops, when the electric circuit breaker is switched ON.

The COMMUTATING-position is the position of the contact piece, in which the movable arcing contacts are aligned with the static arcing contacts. In this position, the ohmic resistance in the arcing branch, in which the movable arcing contacts and the static arcing contacts are located then, reaches its minimum. In addition, the movable main contact is displaced from the static main contacts in this position so that no current can flow through the main branch. In this position, any arcs between the movable main contact and the static main contacts are considered to be quenched.

The ARCING-position is the position of the contact piece, in which the movable arcing contacts are displaced from the static arcing contacts, but in which the distance is not large enough to quench arcs burning between the movable arcing contacts and the static arcing contacts.

The OFF-position is the position of the contact piece, in which the movable main contact is displaced from the static main contacts and the movable arcing contacts are displaced from the static arcing contacts. No current can flow through the main branch, and no current can flow through the arcing branch. In this position, any arcs between the movable main contact and the static main contacts and between the movable arcing contact and the static arcing contacts are considered to be quenched. In particular, the OFF-position is the position, where a movement of the contact piece finally stops, when the electric circuit breaker is switched OFF.

Further advantageous embodiments are disclosed in the claims and in the description as well as in the figures.

Beneficially, all movable arcing contacts are displaced from the at least three static arcing contacts in the ON-position of the movable contact piece. Hence, a current has to flow over the main contacts in the ON-state of the electric circuit breaker. Nevertheless, it is also possible that the movable arcing contacts may be in contact with the static arcing contacts in the ON-position of the movable contact piece in an alternative embodiment. In this case, the movable arcing contacts are in contact with -5 -the static arcing contacts, and the movable main contact is in contact with the two static main contacts in the ON-state of the electric circuit breaker, too.

Advantageously, the electric circuit breaker comprises at least one static main insulator, which is fixedly arranged adjacent to the two static main contacts, wherein the movable main contact is in contact with the at least one static main insulator at least in a partial range between the ON-position and the COMMUTATING-position.

In the above context, it is also of advantage if an air-filled first arc space or a closed air-filled first arc chamber is formed between the contact piece and the at least one static main insulator at least in a position between the ON-position and the COMMUTATING-position, wherein a diameter of the largest virtual circle, which can be inscribed into the first arc space or into the first arc chamber and which has an rotational axis parallel to a movement direction of the contact piece, is smaller than 0.5 mm and in particular is between 0.1 mm and 0.5 mm.

In yet another advantageous embodiment, the electric circuit breaker comprises at least one static arcing insulator, which is fixedly arranged adjacent to the at least three static arcing contacts, wherein each movable arcing contact of the at least two movable arcing contacts is in contact with the at least one static arcing insulator at least in a partial range between the COMMUTATING-position and the OFF-position and in particular in the ARCING-position.

In the above context it is also of advantage, if an air-filled second arc space or a closed air-filled second arc chamber is formed between the contact piece and the at least one static arcing insulator at least in a position or at least in a partial range between the COMMUTATING-position and the OFF-position (in particular in the ARCING-position), wherein a diameter of the largest virtual circle, which can be inscribed into the second arc space or into the second arc chamber and which has an rotational axis parallel to a movement direction of the contact piece, is smaller than 0.5 mm and in particular is between 0.1 mm and 0.5 mm.

The first arc space or the first arc chamber is the air filled space, in which an arc burning between a static main contact and the movable main contact is held. The second arc space or the second arc chamber is the air filled space, in which an arc burning between a static arcing contact and the movable arcing contact is held. -6 -

The first arc space / the first arc chamber and the second arc space / the second arc chamber are general cylinders with cylinder axes parallel to the movement direction of the contact piece. These general cylinders may be hollow as the case may be. The walls of the general cylinder associated with the first arc space or the first arc chamber are formed by the static main insulator at least partly, and the walls of the general cylinder associated with the second arc space or the first arc chamber are formed by the static arcing insulator at least partly.

Because the air gap for the arc is very small in the above spaces or chambers (smaller than 0.5 mm), the arc voltage is comparably high and may rise up to around 100 V/mm. In comparison, the arc voltage in free space is in the region of about 10 V/mm and hence considerably smaller. So, the design of the electric circuit breaker takes advantage of the phenomenon of this arc voltage increase in small air gaps to reduce the distance, which the contact piece has to travel before the arc is quenched. If a particular velocity of the contact piece is given, this also means that the arc is quenched very fast. Viewed from another perspective, this means also that comparably high voltages can be cut off in short time.

Because the arcs burn just for a short time in the above embodiments, parts of the electric circuit breaker (in particular the contact piece as well as the static main insulator and/or the static arcing insulator) are exposed to the arcs for a very short period of time (in particular some milliseconds). Hence, erosion of said parts can be kept low what leads to a long life time of the electric circuit breaker. Beneficially, the at least one static main insulator and/or the at least one static arcing insulator are made from polytetrafluoroethylene (also known as PTFE or Teflon) or a similar material. In this way, the at least one static main insulator and/or the at least one static arcing insulator can withstand the arcs of a lot of switching actions.

It should be noted that beneficially the voltage, which is to be cut off, the velocity of the contact piece and the arc voltage shall have a relation, which leads to short cut off times. In a simplified way, the cut off time teutoff in s can be calculated as follows: tcuto f I -Vcp VUIC VcuL off -7 -wherein Voutoff is the voltage in V, which is to be switched off, vep is the velocity of the contact piece in m/s and V. is the arc voltage in V/m.

Generally, a small but open main arc space can be used to take advantage of the above phenomenon, but it is particularly advantageous if a closed first or second arc chamber is used, in which the arc is held. To allow reduction of the air pressure within the first or second arc chamber and to keep the mechanical load on the structure of the electric circuit breaker in case of an arc low, small relief bores may lead out of the first or second arc chamber.

To form arc chambers, preferably the width or height of the air gap adjacent to the arc chambers is smaller than the width or height of the arc chambers. The air gap between the contact piece and the insulators adjacent to the arc chambers for example can be smaller than 0.1 mm, and in particular can be in a range from 0.02 mm to 0.1 mm.

It should be noted that arcing is not limited to the static arcing contacts and the movable arcing contacts, but arcing can also take place between static main contacts and the movable main contact, however, to a less extent. The reason for arcing between the static main contacts and the movable main contact is that the arcing branch or arcing path over the static arcing contacts and the movable arcing contacts has a considerably higher ohmic resistance than the main branch or main path over the static main contacts and the movable main contact because of the higher number of contact transitions in the arcing branch. Also different contact materials may be a reason for that. So, the current has a tendency to stay in the main branch because of the lower ohmic resistance. Accordingly, the main share of the current flows over the main branch, even if both the arcing branch and the main branch are closed and are conductive in principle. Hence, when the main path is opened, there is still a considerable share of the total current to cut off. The total arc voltage in the main path equals the total ohmic voltage drop in the arcing path. That is why the arcs in the main path are quenched very fast and are less destructive than the arcs in the arcing path, where the total arc voltage equals the voltage of a voltage source connected to the electric circuit breaker which is much higher than the total ohmic voltage drop in the arcing path. -8 -

In particular, the movable main contact gets in contact with the at least one main insulator between the ON-position and the COMMUTATING-position, and then the movable main contact gets displaced from the static main contacts upon further movement of the contact piece towards the COMMUTATING-position. In a first embodiment, the movable main contact is in contact with the at least one static main insulator in the COMMUTATING-position. In a second embodiment, the main contact gets displaced from the at least one static main insulator when the contact piece moves towards the COMMUTATING-position, and the movable main contact is displaced from the static main insulators in the COMMUTATING-position. That means that the movable main contact is moved beyond the at least one static main insulator when the electric circuit breaker commutates. This is particularly useful because then the first arc chamber can easily be opened after arcing and an overpressure in there can be released.

It should be noted that although the use of at least one static main insulator is beneficial, the electric circuit breaker can also be built without a static main insulator. In this case, the movable main contact is surrounded by air after it loses contact to the static main contacts. Such an electric circuit breaker has particularly few parts to mount. It should also be noted that there could also be a single static main insulator with a hole, but it is also possible that the electric circuit breaker comprises a number of static main insulators, wherein in particular each static main insulator is fixedly arranged adjacent to a different one of the two static main contacts. In such a case, the movable main contact gets in contact with a different pair of the static main insulators between the ON-position and the COMMUTATING-position, and then the movable main contact gets displaced from the two static main contacts upon further movement of the contact piece towards the COMMUTATING-position.

In particular, each movable arcing contact of the at least two movable arcing contacts gets in contact with the at least one static arcing insulator at least in a partial range between the COMMUTATING-position and the OFF-position (in particular in the ARCING-position), and then all movable arcing contacts get displaced from the at least three static arcing contacts upon further movement of the contact piece towards the OFF-position. In a first embodiment, each movable arcing contact of the at least two movable arcing contacts is in contact with the at least one static arcing insulator in the OFF-position. In a second embodiment, all movable arcing contacts get -9 -displaced from the static arcing insulators when the contact piece moves towards the OFF-position, and all movable arcing contacts are displaced from the static arcing insulators in the OFF-position. That means that the movable arcing contacts are moved beyond the static arcing insulators when the electric circuit breaker is turned off. This is particularly useful because then the second arc chamber can easily be opened after arcing and an overpressure in there can be released.

It should be noted that although the use of at least one static arcing insulator is beneficial, the electric circuit breaker can also be built without a static arcing insulator. In this case, the movable arcing contacts are surrounded by air after they lose contact to the static arcing contacts. Such an electric circuit breaker has particularly few parts to mount. It should also be noted that there could also be a single static arcing insulator with at least two holes or at least two arcing insulators each with a hole instead. It is also possible that the electric circuit breaker comprises a number of static arcing insulators, wherein each static arcing insulator is fixedly arranged adjacent to a different one of the at least three static arcing contacts. In such a case, each movable arcing contact of the at least two movable arcing contacts gets in contact with a different pair of the static arcing insulators between the COMMUTATING-position and the OFF-position, and then all movable arcing contacts get displaced from the at least three static arcing contacts upon further movement of the contact piece towards the OFF-position.

Generally, the contact piece can be supported in the frame in a linearly movable way or rotatably movable way in relation to the static main contacts and the static arcing contacts. In this way, a linear movement of the contact piece or a rotation of the contact piece is used to change the switching state of the electric circuit breaker. Accordingly, the electric circuit breaker can be adapted to demands with regards to its shape and/or actuator.

Generally, the actuator is an electromagnetic motor, a pneumatic motor, a hydraulic motor or a preloaded spring. In this way, the electric circuit breaker can be adapted to demands with regards to a power source for the actuator.

Advantageously, the two static main contacts, the at least three static arcing contacts, the movable main contact and the at least two movable arcing contacts are -10 -surrounded by air (during operation of the electric circuit breaker). That means no insulating gas like SF6 (sulfur hexafluoride) is needed in this case, and the design of the electric circuit breaker is less technically complicated.

Beneficially, the material used for the two static main contacts and the movable main contact is different from the material used for the at least three static arcing contacts and the movable arcing contacts. In this way, the material chosen for the two static main contacts and the movable main contact can be chosen in view of good conductivity and contact resistance, whereas the material chosen for the at least three static arcing contacts and the movable arcing contacts can be chosen in view of good erosion resistance In yet another beneficial embodiment of the electric circuit breaker, a closed air-filled first arc chamber is formed between the contact piece and at least one static main insulator at least in a position between the ON-position and the COMMUTATING-position, wherein an arc burns between the at least two static main contacts and the movable main contact in a region between the ON-position and the COMMUTATING-position, and an air path within the first arc chamber between the at least two static main contacts and the movable main contact is closed or cut off after the arc is quenched caused by a distance between the at least two static main contacts and the movable main contact. In other words that means that beneficially the arc is quenched before the main contact leaves the first arc chamber space. Afterwards, any current between the two static main contacts and the movable main contact has to flow via the static main insulators. Although this embodiment is advantageous, the arc can also be quenched by closing the first arc chamber. In other words that means that the arc still burns when the main contact leaves the first arc chamber and it is quenched because the current between the two static main contacts and the movable main contact has to flow via the static main insulators then.

Finally, it is advantageous, if a closed air-filled second arc chamber is formed between the contact piece and the static arcing insulators at least in a position or at least in a partial range between the COMMUTATING-position and the OFF-position On particular in the ARCING-position), wherein arcs burn between the at least three static arcing contacts and the movable arcing contacts in a region between the COMMUTATING-position and the OFF-position, and an air path within the second arc chamber between the at least three static arcing contacts and the movable arcing contacts is closed or cut off after the arc is quenched caused by a distance between the at least three static arcing contacts and the movable arcing contacts. In other words that means that beneficially the arc is quenched before the movable arcing contacts leave the second arc chamber. Afterwards, any currents between the at least three static arcing contacts and the movable arcing contacts have to flow via the static arcing insulators. Although this embodiment is advantageous, the arcs can also be quenched by closing the second arc chamber. In other words that means that the arcs still burn when the movable arcing contacts leave the second arc chamber, and they are quenched because the currents between the at least three static arcing contacts and the movable arcing contacts have to flow via the static arcing insulators then.

BRIEF DESCRIPTION OF DRAWINGS

The invention now is described in more detail hereinafter with reference to particular embodiments, which the invention however is not limited to.

Fig. 1 shows a schematic view on an exemplary electric circuit breaker in its ON-state; Fig. 2 shows the electric circuit breaker of Fig. 1 with the contact piece in a second position between the ON-position and the COMMUTATINGposifion; Fig. 3 shows the electric circuit breaker of Fig. 1 with the contact piece in the COMMUTATING-position; Fig. 4 shows the electric circuit breaker of Fig. 1 with the contact piece in a second position between the COMMUTATING-position and an ARCING-position; Fig. 5 shows the electric circuit breaker of Fig. 1 with the contact piece in the ARCING-position; Fig. 6 shows the electric circuit breaker of Fig. 1 with the contact piece in a second position between the ARCING-position and the OFF-position; -12 -Fig. 7 shows the electric circuit breaker of Fig. 1 in its OFF-state; Fig. 8 shows a schematic view on a further exemplary electric circuit breaker which has no static main insulator and no static arcing insulators; Fig. 9 shows a schematic view on a exemplary electric circuit breaker with a rotating contact piece; Fig. 10 shows a detailed cross sectional view of the main contact region from the side; Fig. 11 shows a frontal cross sectional view of the main contact region; Fig. 12 shows a frontal cross sectional view of an open air-filled first arc space and Fig. 13 shows a detailed cross sectional view of the arcing contact region from the side.

DETAILED DESCRIPTION

Generally, same parts or similar parts are denoted with the same/similar names and reference signs. The features disclosed in the description apply to parts with the same/similar names respectively reference signs. Indicating the orientation and relative position (up, down, sideward, etc) is related to the associated figure, and indication of the orientation and/or relative position has to be amended in different figures accordingly as the case may be.

Figs. 1 to 7 show a first embodiment of an electric circuit breaker la in different states. The electric circuit breaker la comprises a frame 2, two static main contacts 3a, 3b fixedly arranged in or on the frame 2 and three static arcing contacts 4a..4c fixedly arranged in or on the frame 2 at a distance from the static main contacts 3a, 3b. Moreover, the electric circuit breaker 1a comprises a first electrical terminal 5a arranged in or on the frame 2, which is electrically connected to a first static main contact 3a of the static main contacts 3a, 3b and a first static arcing contact 4a of the three static arcing contacts 4a. .4c. The electric circuit breaker la also comprises a second electrical terminal 5b arranged in or on the frame 2, which -13 -is electrically connected to a second static main contact 3b of the static main contacts 3a, 3b and a second static arcing contact 4c of the three static arcing contacts 4a..4c. The first and the second electrical terminal 5a, 5b are provided for switching the electric circuit breaker la in a current path 6 of an electric circuit, which furthermore comprises a voltage source 7 in this example. It should be noted, that the electric circuit normally comprises a load, which in this example is left out for the sake of brevity. It should also be noted that the electric circuit may also be part of a multi phase system with or without neutral line, and one or more phases including the neutral line or not may be switched on and off by the electric circuit breaker la.

In addition, the electric circuit breaker la comprises a contact piece 8a, which is movably supported in the frame 2 in relation to the static main contacts 3a, 3b and the static arcing contacts 4a..4c. The electric circuit breaker la also comprises a movable main contact 9 fixedly arranged on the movable contact piece 8a and movable arcing contacts 10a, 10b fixedly arranged on the movable contact piece 8a at a distance from the movable main contact 9 and electrically insulated thereof. Generally, the count of the movable arcing contacts 10a, 10b equals the count of the static arcing contacts 4a..4c minus one. Accordingly, there are two movable arcing contacts 10a, 10b in this example. Furthermore, the electric circuit breaker la comprises a coil 11 fixedly arranged in relation to the frame 2 and a magnet 12 mounted on or in the movable contact piece 8a. The coil 11 together with the magnet 12 forms an actuator 13a of the electric circuit breaker la, which is designed to move the contact piece 8a from an ON-position to an OFF-position via a COMMUTATING-position.

Furthermore, the electric circuit breaker la comprises optional static main insulators 14a, 14b in this example, which are fixedly arranged next to the static main contacts 3a, 3b. In detail, the static main insulator 14a is located next to the static main contact 4a and the static main insulator 14b is located next to the static main contact 3b.

In addition, the electric circuit breaker la comprises a number of optional static arcing insulators 15a..15c in this example, wherein each of them is fixedly arranged adjacent to a different one of the three static arcing contacts 4a..4c. In detail, the static arcing insulator 15a is located next to the static arcing contact 4a, the static -14 -arcing insulator 15b is located next to the static arcing contact 4b and the static arcing insulator 15c is located next to the static arcing contact 4c.

As said, Figs. 1 to 7 show the electric circuit breaker la in different states. The different states are defined by the positions P1.. P7 of the movable contact piece 8a, wherein the movement of the movable contact piece 8a is caused by the actuator 13a. When an current flows through the coil 11, the magnet 12 and hence the movable contact piece 8a is moved or pushed to the left side. Said current may be switched on when for example an overcurrent condition or an overtemperature condition occurs or when the electric circuit breaker la shall be switched off intentionally.

In detail, Fig. 1 shows the movable contact piece 8a at a first position P1, which equals the ON-position of the movable contact piece 8a or the ON-state of the electric circuit breaker la. In this state or position, the movable main contact 9 is in contact with the two static main contacts 3a, 3b, and current may flow through the electric circuit formed by the current path 6, the voltage source 7, the conductor between the first electrical terminal 5a and the first static main contact 3a, the conductor between the second electrical terminal 5b and the second static main contact 3b, the static main contacts 3a, 3b and the movable main contact 9.

Fig. 2 shows the movable contact piece 8a at a second position P2 between the ON-position of the movable contact piece 8a and its COMMUTATING-position. As can be seen, each movable arcing contact 10a, 10b of the at least two movable arcing contacts 10a, 10b got in contact with a different pair of the three static arcing contacts 4a..4c. In detail, the first movable arcing contact 10a is in contact with the static arcing contacts 4a and 4c, and the second movable arcing contact 10b is in contact with the static arcing contacts 4b and 4c. In addition, the movable main contact 9 is still in contact with the two static main contacts 3a, 3b in this state. Accordingly, current may flow both over the movable main contact 9 and the two static main contacts 3a, 3b and the movable arcing contacts 10a, 10b and the static arcing contacts 4a..4c.

Fig. 3 shows the movable contact piece 8a at a third position P3 which equals the COMMUTATING-position of the movable contact piece 8a or the COMMUTATING- -15 -state of the electric circuit breaker la. In this state or position, the movable main contact 9 got displaced from the two static main contacts 3a, 3b. Accordingly, current can only flow over the movable arcing contacts 10a, 10b and the static arcing contacts 4a..4c.

It should also be noted in this context that arcing is not limited to the static arcing contacts 4a..4c and the movable arcing contacts 10a, 10b, but arcing can also take place between static main contacts 3a, 3b and the movable main contact 9, however, to a less extent. The reason for arcing between the static main contacts 3a, 3b and the movable main contact 9 is that the arcing branch or arcing path over the static arcing contacts 4a..4c and the movable arcing contacts 10a, 10b has a considerably higher ohmic resistance than the main branch or main path over the static main contacts 3a, 3b and the movable main contact 9 because of the higher number of contact transitions in the arcing branch. Also different contact materials may be a reason for that. So, the current has a tendency to stay in the main branch because of the lower ohmic resistance. Accordingly, the main share of the current flows over the main branch, even if both the arcing branch and the main branch are closed and are conductive in principle. Hence, when the main path is opened, there is still a considerable share of the total current to cut off. The total arc voltage in the main path equals the total ohmic voltage drop in the arcing path. That is why the arcs in the main path are quenched very fast and are less destructive than the arcs in the arcing path, where the total arc voltage equals the voltage of the voltage source 7 which is much higher than the total ohmic voltage drop in the arcing path. For the above reasons, it is useful to provide the static main insulators 14a, 14b as this is shown in the Figs. 1 to 8 (see also the explanations associated with the Figs. 10 to 12).

Fig. 4 shows the movable contact piece 8a at a fourth position P4. As can be seen, each movable arcing contact 10a, 10b got in contact with a different pair of the static arcing insulators 15a..15c. In detail, the first movable arcing contact 10a is in contact with the static arcing insulators 15a and 15c, and the second movable arcing contact 10b is in contact with the static arcing insulators 15b and 15c. In addition, the movable arcing contacts 10a, 10b are still in contact with the static arcing contacts 4a..4c in this state. Accordingly, current may still flow over the movable -16 -arcing contacts 10a, 10b and the static arcing contacts 4a..4c. However, resistance increases during the movement of the movable contact piece 8a.

Fig. 5 shows the movable contact piece 8a at a fifth position P5 which equals the ARCING-position of the movable contact piece 8a or the ARCING-state of the electric circuit breaker la. In this position or state, all movable arcing contacts 10a, 10b got displaced from the static arcing contacts 4a..4c, and current must flow over the static arcing insulators 15a and 15c and/or over the air gaps between the movable arcing contacts 10a, 10b and the static arcing contacts 4a..4c. Accordingly, arcs are generated between the movable arcing contacts 10a, 10b and the static arcing contacts 4a..4c. In detail, a first arc is ignited between the static arcing contact 4a and the movable arcing contact 10a, a second one is ignited between the movable arcing contact 10a and the static arcing contact 4c, a third one is ignited between the static arcing contact 4c and the movable arcing contact 10b and a fourth one is ignited between the movable arcing contact 10b and the static arcing contact 4b.

Fig. 6 shows the movable contact piece 8a at a sixth position P6. In this state, the movable arcing contacts 10a, 10b got further displaced from the static arcing contacts 4a..4c and thus the air gaps increased as well.

Somewhere between the fifth position P5 and the seventh position P7 of the movable contact piece 8a, which is shown in Fig. 7, the arcs between the movable arcing contacts 10a, 10b and the static arcing contacts 4a..4c get quenched and thus no current can flow through the electric circuit. Hence, the seventh position P7 equals the OFF-position of the movable contact piece 8a or the OFF-state of the electric circuit breaker la. As can be seen, each movable arcing contact 10a, 10b lost contact to the static arcing insulators 15a and 15c in this state and in this example.

Because of the current commutation between the first position P1 and the third position P3 of the movable contact piece 8a, there is no or not much arcing between the movable main contact 9 and the static main contacts 3a, 3b. In contrast, arcing is limited or substantially limited to the movable arcing contacts 10a, 10b and the static arcing contacts 4a..4c.

-17 -Advantageously, there is a comparably high number of arcs or air gaps based on the number of movable arcing contacts 10a, 10b and static arcing contacts 4a..4c. In detail, the number of arcs or air gaps equals twice the number movable arcing contacts 10a, 10b. The invention is not limited to two movable arcing contacts 10a, 10b and three static arcing contacts 4a..4c, but any desired number of movable arcing contacts 10a, 10b and static arcing contacts 4a..4c may be chosen in accordance with the voltage, which is to be switched off and in accordance with the travel distance of the movable contact piece 8a from the fifth position P5 or ARCING-position to the position, where the arcs are actually quenched. A further advantage is that the movable main contact 9 and the two static main contacts 3a, 3b are not deteriorated much by arcing so that a low contact resistance can be guaranteed over a long period of time. The electric circuit breaker la is particularly usable in DC applications, but it may also used in AC applications or mixed DC/AC applications.

It should be noted that the magnet 12 is out of the coil 11 from the third position P3 of the movable contact piece 8a onwards in this example. So, in this example the inertia of the movable contact piece 8a is used to cause a further movement. It should also be noted, that the Figs. 1 to 7 are just schematic drawings of an electric circuit breaker la, and the magnet 12 may be longer than depicted and can stay within the coil 11 over the whole movement of the movable contact piece 8a. It should also be noted that the coil 11 usually is mounted to the frame 2 although this is not depicted in the Figs. 1 to 7. Moreover, the electric circuit breaker la may comprise means for a back movement of the movable contact piece 8a from the seventh position P7 to the first position P1. For example, the actuator 13a or a spring may be used for this reason. It should also be noted that the frame 2 can be arranged within a housing of the electric circuit breaker 1a, can be an integral part of a housing of the electric circuit breaker la or can form a housing of the electric circuit breaker la as such.

In the embodiment depicted in Figs. 1 to 7, all movable arcing contacts 10a, 10b are displaced from the at least three static arcing contacts 4a..4c in the first position P1 or ON-position of the movable contact piece 8a. Nonetheless, the movable arcing contact 10a, 10b may be in contact with the static arcing contacts 4a..4c in the first position Pb or ON-position of the movable contact piece 8a in an alternative embodiment. It should be noted that then the movable arcing contact 10a, 10b are in -18 -contact with the static arcing contacts 4a. .4c and the movable main contact 9 is in contact with the two static main contacts 3a, 3b.

In another embodiment, the static arcing insulators 15a..15c can be made longer than depicted so that the movable arcing contacts 10a, 10b are still in contact with the static arcing insulators 15a..15c in the seventh position P7 or OFF-position of the movable contact piece 8a.

In yet another embodiment, the static arcing insulators 15a..15c can be omitted so that the movable arcing contact 10a, 10b after losing contact to the static arcing contacts 4a..4c are surrounded by air. Alternatively or in addition, the static main insulators 14a, 14b can be omitted so that the movable main contact 9 after losing contact to the static main contacts 3a, 3b are surrounded by air. An embodiment for a electric circuit breaker lb without static main insulators 14a, 14b and without static arcing insulators 15a..15c is shown in Fig. B. Generally, it should be noted that the two static main contacts 3a, 3b, the at least three static arcing contacts 4a. .4c, the movable main contact 9 and the at least two movable arcing contacts 10a, 10b are surrounded by air during operation of the electric circuit breaker la. That means no insulating gas like SF6 (sulfur hexafluoride) is needed in this case.

In the above examples, the actuator 13a is embodied as a (linear) electromagnetic motor. This is however no necessary condition, and the actuator 13a may also embodied as a pneumatic motor, a hydraulic motor or a preloaded spring as the case may be.

Furthermore, the movable contact piece 8a is supported in the frame 2 in a linearly movable way. Nevertheless, the movable contact piece 8a can be supported in the frame 2 also in a rotatably movable way as this is case for the embodiment of the electric circuit breaker lc depicted in Fig. 9.

In this embodiment, the movable contact piece 8b is embodied as a segment disk, which may be rotated around the rotation axis A by the rotational actuator 13b, which again may be embodied as an electromagnetic motor, a pneumatic motor, a hydraulic motor or a preloaded spring. Upon a rotation, the contact piece 8b travels -19 -through the positions P1..P7 and the electric circuit breaker 1c reaches the different states just like it is depicted in Figs. 1 to 7 for the electric circuit breaker la. It should be noted that a frame 2 is not explicitly depicted in Fig. 9 for the sake of simplicity. Nonetheless, the movable contact piece 8a is supported in the frame 2 in a rotatably movable way in reality.

In the embodiment of Fig. 9, the static main contacts 3a, 3b, the static arcing contacts 4a..4c the movable main contact 9, the movable arcing contacts 10a, 10b and the static arcing insulators 15a..15c are arranged in a (single) plane. This is however no necessary condition, and the static main contacts 3a, 3b, the static arcing contacts 4a..4c the movable main contact 9, the movable arcing contacts 10a, 10b and the static arcing insulators 15a..15c may be arranged in different planes, which are spaced from one another in the direction of the rotation axis A, as well.

Although, in the example of Fig. 9 there are no static main insulators 14a, 14b, of course it is also possible to have static main insulators 14a, 14b in this rotational arrangement.

In the examples shown in the Figures, a linear movable contact piece 8a is moved by a linear actuator 13a and a rotatable contact piece 8b is moved by a rotational actuator 13b. Nevertheless it is also possible that a linear movable contact piece 8a is moved by a rotational actuator 13b and vice versa.

One should also note that the ON-state, the COMMUTATING-state, the ARCING-state and the OFF-state of the electric circuit breaker 1a..1c are not linked to single positions of the contact piece 8a, 8b, but rather to ranges. Accordingly, the ON-position, the COMMUTATING-position, the ARCING-position and the OFF-position of the contact piece 8a, 8b could also be seen as an ON-range, a COMMUTATING-range, an ARCING-range and an OFF-range of the contact piece 8a, 8b or a bunch of ON-positions, COMMUTATING-positions, ARCING-positions and OFF-positions. From this viewpoint, a single ON-position, COMMUTATING-position, ARCING-position and OFF-position of the contact piece 8a, 8b is a simplification to keep the disclosure concise.

-20 -It should also be noted that although the static main insulators 14a, 14b can be embodied as separate pieces as depicted in the Figs., there could also be a single insulator with a single hole instead. The very same counts for the static arcing insulators 15a..15c. Although the static arcing insulators 15a..15c can be embodied as separate pieces as depicted in the Figs., there could also be a single insulator with two holes or two insulators each with a hole instead. Of course, those embodiments vary with the number of the static arcing contacts 4a. .4c.

Figs. 10 and 11 now show a detailed view of the main contact region. Fig. 10 shows a cross sectional view from the side, and Fig. 11 shows a frontal cross sectional view. As can be seen in Figs. 10 and 11 in detail, a closed air-filled first arc chamber B is formed between the contact piece 8a and the at least one static main insulator 14a, 14b (and the static main contacts 3a, 3b) at least in a position between the ON-position P1 and the COMMUTATING-position P3. Here a state is shown, where the movable main contact 9 is positioned at a distance from the static main contacts 3a, 3b. As disclosed hereinbefore, arcing can take place between the movable main contact 9 and the static main contacts 3a, 3b, and Fig. 10 shows a situation, in which this happens as indicated by the arcs C. The first arc chamber B is an air filled space, in which arcs C burning between a static main contact 3a, 3b and the movable main contact 9 are held. The first arc chamber B is a general cylinder with an cylinder axis parallel to the movement direction of the contact piece 8a. In this case, this general cylinder is a hollow one. The walls of the general cylinder associated with the first arc chamber B are formed by the contact piece 8a and the at least one static main insulator 14a, 14b (and the static main contacts 3a, 3b).

Advantageously, a diameter di of the largest virtual circle D, which can be inscribed into the first arc chamber B and which has an rotational axis parallel to a movement direction of the contact piece 8a, is smaller than 0.5 mm and in particular is between 0.1 mm and 0.5 mm. The diameter di corresponds to the width or height hi of the air gap here, which is the difference of the outer radius and the inner radius of the general cylinder forming the first arc chamber B in this example. However, this is no necessary condition, and the diameter di can differ from the width or height hi depending on the shape of the air gap. To form a first arc chamber B, the width or -21 -height of the air gap between the contact piece 8a and the static main insulators 14a, 14b in a region adjacent to the first arc chamber B is smaller than the width or height hi of the first arc chamber B (for example < 0.1 mm).

Because of this small size of the air gap for the arc C, the arc voltage is comparably high and may rise up to around 100 V/mm. Hence, also the distance, which the contact piece 8a has to travel before the arc C is quenched, is small, of course depending on the voltage of the voltage source 7. Viewed from another perspective, this means also that comparably high voltages can be cut off in short time if a particular velocity of the contact piece 8a is given. So, the design of the electric circuit breaker la takes advantage of the phenomenon of the increased arc voltage in small air gaps. Usually, the length 11 of the first arc chamber B is about some millimeters (e.g. <5 mm).

Because the arc C burns just for a short time in this embodiment, parts of the electric circuit breaker la (here in particular the contact piece 8a as well as the static main insulators 14a, 14b) are exposed to the arc C for a very short period of time (in particular some milliseconds). Hence, erosion of said parts can be kept low leading to a long life time of the electric circuit breaker la. Beneficially, the static main insulators 14a, 14b are made from polytetrafiuoroethylene (also known as PTFE or Teflon) or a similar material. In this way, the static main insulators 14a, 14b can withstand the arcs C of a lot of switching actions.

Beneficially, an air path within the first arc chamber B between the static main contacts 3a, 3b and the movable main contact 9 is closed or cut off after the arc C is quenched caused by a distance between the at least two static main contacts 3a, 3b and the movable main contact 9. In other words that means that beneficially the arc C is quenched before the main contact 9 leaves the first arc chamber B (afterwards, any current between the two static main contacts 3a, 3b and the movable main contact 9 has to flow via the static main insulators 14a, 14b). Although this embodiment is advantageous, the arc C can also be quenched by closing the first arc chamber B. In other words that means that the arc C still burns when the main contact 9 leaves the first arc chamber B, and it is quenched because the current between the two static main contacts 3a, 3b and the movable main contact 9 has to flow via the static main insulators 14a, 14b then.

-22 -To allow reduction of the air pressure within the first arc chamber B and to keep the mechanical load on the structure of the electric circuit breaker la in case of an arc C low, small optional relief bores 16 may lead out of the first arc chamber B as this is depicted in Fig. 11.

In the example of Figs. 10 and 11, the two static main insulators 14a, 14b form halves of a cylindrical sleeve. This is however no necessary condition, and the static main insulator 14a, 14b may also be one part. In addition, the proposed measures are not limited to cylindrical cross sections, but the cross section of the parts in question (e.g. contact piece 8a, main insulators 14a, 14b) may also be polygonal, in particular rectangular or quadratic.

It should also be noted that the use of a first closed arc chamber B is not mandatory. Instead, a more open air-filled first arc space E can be used. An example for that is depicted in Fig. 12. The air gap has the same width or height as in the example of Fig. 11, but the air gap is open at its sides. Still an arc C can be kept within a small space and still the arc voltage is comparably high compared to open space. However, the arc voltage in the embodiment of Fig. 12 is a bit lower than in the embodiment of Fig. 12. Because of missing sidewalls, also release bores 16 can be omitted in this case.

Fig. 13 finally shows a detailed cross sectional view of the arcing contact region from the side. The situation is comparable to the main contact region depicted in Fig. 10. However, in contrast, the contact piece 8a has a tapering to form a closed air-filled second arc chamber F between the contact piece 8a and the static arcing insulators 15a..15c (and the static arcing contacts 4a..4c) at least in a position between the COMMUTATING-position P3 and the OFF-position P7. Here a state is shown, where the movable arcing contacts 10a, 10b are positioned at a distance from the static arcing contacts 4a. .4c and where arcs C burn between the same.

Generally, the technical disclosure presented in the context of the main contact region equally applies to the arcing contact region. Again there is an air filled second arc chamber F in the shape of a general (hollow) cylinder or an air filled second arc space E (see Fig. 12).

-23 -Advantageously, a diameter d2 of the largest virtual circle D, which can be inscribed into the second arc chamber F and which has an rotational axis parallel to a movement direction of the contact piece 8a, is smaller than 0.5 mm and in particular is between 0.1 mm and 0.5 mm for the same reasons. The same counts for the air gap between the contact piece 8a and the static arcing insulators 15a..15c in a region adjacent to the second arc chamber F which preferably is smaller than the width or height h2 of the second arc chamber F (for example <0.1 mm).

Again, the arcs C can be cut off very fast because of the high arc voltage. However, of course the deleterious effects of the arcs C in the arcing contact region are much higher than in the main contact region because the voltage and the current to cut off here are much higher. But still, erosion of parts of the electric circuit breaker la (here in particular the contact piece 8a as well as the static arcing insulators 15a..15c) can kept comparably low.

Again, optional relief bores 16 may lead out of the second arc chamber F, and the static arcing insulators 15a..15c can be one part or multi part. And again, an air path within the second arc chamber F between the static arcing contacts 4a..4c and the movable arcing contacts 10a, 10b can be closed or cut off after the arc C is quenched caused by a distance between the static arcing contacts 4a..4c and the movable arcing contacts 10a, 10b. Alternatively, the arc C can also be quenched by closing the second arc chamber F. It should be noted that generally the material used for the two static main contacts 3a, 3b and the movable main contact 9 can be different from the material used for the at least three static arcing contacts 4a..4c and the movable arcing contacts 10a, 10b. In this way, the material chosen for the two static main contacts 3a, 3b and the movable main contact 9 can be chosen in view of good conductivity and contact resistance, whereas the material chosen for the at least three static arcing contacts 4a..4c and the movable arcing contacts 10a, 10b can be chosen in view of good erosion resistance.

Furthermore, it is noted that the invention is not limited to the embodiments disclosed hereinbefore, but combinations of the different variants are possible. In reality, the electric circuit breaker la.. 1c may have more or less parts than shown in the figures.

-24 -The electric circuit breaker la..1c as well as parts thereof may also be shown in different scales and may be bigger or smaller than depicted. Finally, the description may comprise subject matter of further independent inventions.

It should also be noted that the term "comprising" does not exclude other elements and the use of articles "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

LIST OF REFERENCE NUMERALS

1a..1c electric circuit breaker 2 frame 3a, 3b static main contacts 4a. .4c static arcing contacts 5a, 5b electrical terminal 6 current path 7 voltage source 8a, 8b contact piece 9 movable main contact 10a, 10b movable arcing contact 11 coil 12 magnet 13a, 13b actuator 14a, 14b static main insulator 15a..15c static arcing insulator 16 relief bore di, d2 diameter of virtual circle It 12 length of air gap hi, h2 height of air gap A axis first arc chamber arc virtual circle first arc space second arc chamber P1 P7 contact piece position -25 -

Claims

-26 -CLAIMS1. Electric circuit breaker (1a..1c), comprising a frame (2), two static main contacts (3a, 3b) fixedly arranged in or on the frame (2), at least three static arcing contacts (4a. .4c) fixedly arranged in or on the frame (2) at a distance from the static main contacts (3a, 3b), a first electrical terminal (5a) arranged in or on the frame (2), which is electrically connected to a first of the static main contacts (3a, 3b) and a first of said at least three static arcing contacts (4a. .4c), - a second electrical terminal (5b) arranged in or on the frame (2), which is electrically connected to a second of the static main contacts (3a, 3b) and a second of said at least three static arcing contacts (4a. .4c), wherein the first and the second electrical terminal (5a, 5b) are provided for switching the electric circuit breaker (1a..1c) in a current path (6) of an electric circuit, a contact piece (8a, 8b) which is movably supported in the frame (2) in relation to the static main contacts (3a, 3b) and the static arcing contacts (4a. .4c), a movable main contact (9) fixedly arranged on the movable contact piece (8a, 8b), - movable arcing contacts (10a, 10b) fixedly arranged on the movable contact piece (8a, 8b) at a distance from the movable main contact (9) and electrically insulated thereof, wherein the count of the movable arcing contacts (10a, 10b) equals the count of the static arcing contacts (4a..4c) minus one and - an actuator (13a, 13b), which is designed to move the contact piece (8a, 8b) from an ON-position (P1) to an OFF-position (P7) via a COMMUTATING-position (P3), wherein the movable main contact (9) is in contact with the two static main contacts (3a, 3b) in the ON-position (P1), wherein the movable main contact (9) is displaced from the two static main contacts (3a, 3b) in the COMMUTATING-position (P3) and wherein each movable arcing contact (10a, 10b) of the at least two movable arcing contacts (10a, 10b) is in contact with a different pair of the at least three static arcing contacts (4a. .4c) in the COMMUTATING-position (P3) and -27 -wherein the movable main contact (9) is displaced from the two static main contacts (3a, 3b) in the OFF-position (P7) and wherein all movable arcing contacts (10a, 10b) are displaced from the at least three static arcing contacts (4a..4c) in the OFF-position (P7), too.
2. Electric circuit breaker (1a..1c) as claimed in claim 1, characterized in that all movable arcing contacts (10a, 10b) are displaced from the at least three static arcing contacts (4a..4c) in the ON-position (P1).
3. Electric circuit breaker (1a..1c) as claimed in claim 1 or 2, characterized in that the electric circuit breaker (1a..1c) comprises at least one static main insulator (14a, 14b), which is fixedly arranged adjacent to the two static main contacts (3a, 3b), and in that the movable main contact (9) is in contact with the at least one static main insulator (14a, 14b) at least in a partial range between the ON-position (P1) and the COMMUTATING-position (P3).
4. Electric circuit breaker (1a..1c) as claimed in claim 3, characterized in that a closed air-filled first arc chamber (B) or an air-filled first arc space (E) is formed between the contact piece (8a, 8b) and the at least one static main insulator (14a, 14b) at least in a position or at least in a partial range between the ON-position (P1) and the COMMUTATING-position (P3), wherein a diameter (di) of the largest virtual circle (D), which can be inscribed into the first arc chamber (B) or into the first arc space (E) and which has an rotational axis parallel to a movement direction of the contact piece (8a, 8b), is smaller than 0.5 mm.
5. Electric circuit breaker (1a..1c) as claimed in any one of claims 1 to 4, characterized in that the electric circuit breaker (1a..1c) comprises at least one static arcing insulator (15a..15c), which is fixedly arranged adjacent to the at least three static arcing contacts (4a..4c), and in that each movable arcing contact (10a, 10b) of the at least two movable arcing contacts (10a, 10b) is in contact with the at least one static arcing insulator (15a..15c) at least in a partial range between the COMMUTATING-position (P3) and the OFF-position (P7).
-28 - 6. Electric circuit breaker (1a..1c) as claimed in claim 5, characterized in that a closed air-filled second arc chamber (F) or an air-filled second arc space is formed between the contact piece (8a, 8b) and the at least one static arcing insulator (15a..15c) at least in a position or at least in a partial range between the COMMUTATING-position (P3) and the OFF-position (P7), wherein a diameter (d2) of the largest virtual circle, which can be inscribed into the second arc chamber (F) or into the second arc space and which has an rotational axis parallel to a movement direction of the contact piece (8a, 8b), is smaller than 0.5 mm.
7. Electric circuit breaker (1a..1c) as claimed in any one of claims 3 to 6, characterized in that the movable main contact (9) is in contact with the static main insulators (14a, 14b) in the COMMUTATING-position (P7) or the movable main contact (9) is displaced from the static main insulators (14a, 14b) in the COMMUTATING-position (P7).
8. Electric circuit breaker (1a..1c) as claimed in any one of claims 5 to 7, characterized in that all movable arcing contacts (10a, 10b) are in contact with the static arcing insulators (15a..15c) in the OFF-position (P7) or all movable arcing contacts (10a, 10b) are displaced from the static arcing insulators (15a..15c) in the OFF-position (P7).
9. Electric circuit breaker (1a.. 1c) as claimed in any one of claims 1 to 8, characterized in that the contact piece (8a, 8b) is supported in the frame (2) in a linearly movable way or rotatably movable way in relation to the static main contacts (3a, 3b) and the static arcing contacts (4a. .4c).
10. Electric circuit breaker (1a..1c) as claimed in any one of claims 1 to 9, characterized in that the actuator (13a, 13b) is an electromagnetic motor, a pneumatic motor, a hydraulic motor or a preloaded spring.
-29 - 11. Electric circuit breaker (1a..1c) as claimed in any one of claims 1 to 10, characterized in that the two static main contacts (3a, 3b), the at least three static arcing contacts (4a..4c), the movable main contact (9) and the at least two movable arcing contacts (10a, 10b) are surrounded by air.
12. Electric circuit breaker (1a..1c) as claimed in any one of claims 1 to 11, characterized in that the material used for the two static main contacts (3a, 3b) and the movable main contact (9) is different from the material used for the at least three static arcing contacts (4a..4c) and the movable arcing contacts (10a, 10b).
13. Method of switching OFF an electric circuit breaker (1a..1c), which comprises a frame (2), two static main contacts (3a, 3b) fixedly arranged in or on the frame (2), at least three static arcing contacts (4a..4c) fixedly arranged in or on the frame (2) at a distance from the static main contacts (3a, 3b), a first electrical terminal (5a) arranged in or on the frame (2), which is electrically connected to a first of the static main contacts (3a, 3b) and a first of said at least three static arcing contacts (4a..4c), a second electrical terminal (5b) arranged in or on the frame (2), which is electrically connected to a second of the static main contacts (3a, 3b) and a second of said at least three static arcing contacts (4a..4c), wherein the first and the second electrical terminal (5a, 5b) are provided for switching the electric circuit breaker (1a..1c) in a current path (6) of an electric circuit, a contact piece (8a, 8b) which is movably supported in the frame (2) in relation to the static main contacts (3a, 3b) and the static arcing contacts (4a..4c), a movable main contact (9) fixedly arranged on the movable contact piece (8a, 8b), movable arcing contacts (10a, 10b) fixedly arranged on the movable contact piece (8a, 8b) at a distance from the movable main contact (9) and electrically insulated thereof, wherein the count of the movable arcing contacts (10a, 10b) equals the count of the static arcing contacts (4a..4c) minus one and an actuator (13a, 13b), which upon a switching command moves the contact piece (8a, 8b) from an ON-position (Pb) to an OFF-position (P7) via a -30 -COMMUTATING-position (P3), - wherein the movable main contact (9) is in contact with the two static main contacts (3a, 3b) in the ON-position (P1), - wherein each movable arcing contact (10a, 10b) of the at least two movable arcing contacts (10a, 10b) gets in contact with a different pair of the at least three static arcing contacts (4a..4c) before the movable main contact (9) gets displaced from the two static main contacts (3a, 3b) between the ON-position (P1) and the COMMUTATING-position (P3), wherein the movable main contact (9) is displaced from the two static main contacts (3a, 3b) in the COMMUTATING-position (P3) and wherein each movable arcing contact (10a, 10b) of the at least two movable arcing contacts (10a, 10b) is in contact with a different pair of the at least three static arcing contacts (4a..4c) in the COMMUTATING-position (P3) and wherein all movable arcing contacts (10a, 10b) get displaced from the at least three static arcing contacts (4a..4c) between the COMMUTATING-position (P3) and the OFF-position (P7) and wherein the movable main contact (9) is displaced from the two static main contacts (3a, 3b) in the OFF-position (P7) and wherein all movable arcing contacts (10a, 10b) are displaced from the at least three static arcing contacts (4a..4c) in the OFF-position (P7), too.
14. Method as claimed in claim 13, characterized in that a closed air-filled first arc chamber (B) is formed between the contact piece (8a, 8b) and at least one static main insulator (14a, 14b) at least in a position or at least in a partial range between the ON-position (P1) and the COMMUTATING-position (P3), wherein an arc (C) burns between the at least two static main contacts (3a, 3b) and the movable main contact (9) in a region between the ON-position (P1) and the COMMUTATING-position (P3), and an air path within the first arc chamber (B) between the at least two static main contacts (3a, 3b) and the movable main contact (9) is closed or cut off after the arc (C) is quenched caused by a distance between the at least two static main contacts (3a, 3b) and the movable main contact (9).-31 -
15. Method as claimed in claim 13 or 14, characterized in that a closed air-filled second arc chamber (F) is formed between the contact piece (8a, 8b) and the static arcing insulators (15a..15c) at least in a position or at least in a partial range between the COMMUTATING-position (P3) and the OFF-position (P7), wherein an arc (C) burns between the at least three static arcing contacts (4a. .4c) and the movable arcing contacts (10a, 10b) in a region between the COMMUTATING-position (P3) and the OFF-position (P7), and an air path within the second arc chamber (F) between the at least three static arcing contacts (4a..4c) and the movable arcing contacts (10a, 10b) is closed or cut off after the arc (C) is quenched caused by a distance between the at least three static arcing contacts (4a. .4c) and the movable arcing contacts (10a, 10b).