WO2017063683A1

WO2017063683A1 - Alternating current contactor

Info

Publication number: WO2017063683A1
Application number: PCT/EP2015/073737
Authority: WO
Inventors: Magnus Backman; Lars Liljestrand; Gunnar Johansson
Original assignee: Abb Schweiz Ag
Priority date: 2015-10-14
Filing date: 2015-10-14
Publication date: 2017-04-20

Abstract

The present disclosure relates to an AC contactor (1), comprising a first fixed contact member (3a), a second fixed contact member (3b), a movable contact bridge member (5) mechanically connectable to the first fixed contact member (3a) and to the second fixed contact member (3b) simultaneously to allow current (i) to flow between the first fixed contact member (3a) and the second fixed contact member (3b), and which movable contact bridge member (5) is arranged to be moved away from the first fixed contact member (3a) and the second fixed contact member (3b) to obtain an open state of the AC contactor (1), and a first reverse-blocking semiconductor device (7) arranged to provide a current path (9) in the forward direction of the first reverse-blocking semiconductor device (7), in the open state of the AC contactor (1), from the first fixed contact member (3a) to the movable contact bridge member (5).

Description

ALTERNATING CURRENT CONTACTOR

TECHNICAL FIELD

The present disclosure generally relates to AC contactors. In particular, it relates to an AC contactor that includes a diode for arc extinguishing.

BACKGROUND

Today, standard low voltage (LV) alternating current (AC) contactors typically use a moving contact bridge member and two fixed contact members for each phase. When the contact opens, two arcs are created and eventually commutated to arc splitters. The arc is then divided into a number of small arcs in series, increasing the arc voltage and at next current zero crossing the current is interrupted.

The present conventional solution requires a careful design of contact system and arc splitters in order to obtain the right interruption capability. Problems with these solution often involve re-ignitions after interruption at current zero, high contact erosion and a bulky design.

EP0872861 discloses an electrical device with double AC breaking contacts. The breaker includes a box with several conducting paths with electrical contacts and a controller. A conducting path includes two fixed contacts connected to terminals via conductors. A contact bridge can be actuated by the controller. The bridge has two mobile contacts cooperating with the fixed ones. Two diodes ensure current flows towards the two terminals.

SUMMARY

The solution disclosed in EP0872861 includes diode connections across the movable contact bridge, which, because of the movable character of the contact bridge member may be complicated to implement. Moreover, the wires of the diodes cross each other, and these wires may have differing electrical potential. It may therefore be required that the wires be provided with increased electrical insulation and/or be placed at a certain minimum distance from each other.

In view of the above, an object of the present disclosure is to provide an AC contactor which solves or at least mitigates the problems with existing solution.

There is hence provided an alternating current, AC, contactor, comprising a first fixed contact member, a second fixed contact member, a movable contact bridge member mechanically connectable to the first fixed contact member and to the second fixed contact member simultaneously in a closed state of the AC contactor to allow current to flow between the first fixed contact member and the second fixed contact member, and which movable contact bridge member is arranged to be moved away from the first fixed contact member and the second fixed contact member to obtain an open state of the AC contactor, and a first reverse-blocking semiconductor device arranged to provide a current path in the forward direction of the first reverse-blocking semiconductor device, in the open state of the AC contactor, from the first fixed contact member to the movable contact bridge member.

An effect which may be obtainable thereby is a simpler construction because no reverse-blocking semiconductor device wire has to be moved across the movable contact. This effect may be obtained because the reverse-blocking semiconductor device carries current from the first fixed contact member to the movable contact bridge member, instead of carrying current from a fixed contact member to the other fixed contact member like in the above- discussed prior art document. According to one embodiment the first reverse-blocking semiconductor device is mounted onto the first fixed contact member and located beside the movable contact bridge member at a first fixed contact member side of the movable contact bridge member.

According to one embodiment the first reverse-blocking semiconductor device is connectable to the movable contact bridge member by arcing. According to one embodiment the movable contact bridge member has a first portion galvanically connectable to the first fixed contact member, and wherein the first reverse-blocking semiconductor device has a first leg, which first leg in the open state of the AC contactor extends towards the first portion of the movable contact bridge member to enable arcing between the first leg and the first portion of the movable contact bridge member.

According to one embodiment the first reverse-blocking semiconductor device is galvanically connected to the movable contact bridge member.

According to one embodiment the first reverse-blocking semiconductor device is galvanically connected to the movable contact bridge member by means of a first flexible conductor.

One embodiment comprises a second reverse-blocking semiconductor device arranged to provide a current path in the forward direction of the second reverse-blocking semiconductor device, in the open state of the AC contactor, from the second fixed contact member to the movable contact bridge member, which first reverse-blocking semiconductor device and second reverse-blocking semiconductor device are connected in antiparallel. Thus in case of two reverse-blocking semiconductor devices, by means of this design there is no crossing of reverse-blocking semiconductor device wires and there are no reverse-blocking semiconductor device wires crossing the movable contact bridge member. As a result, the amount of electrical insulation of the reverse-blocking semiconductor device wires may be reduced and the entire AC contactor design may be made more compact.

According to one embodiment the second reverse-blocking semiconductor device is mounted onto the second fixed contact member and located beside the movable contact bridge member at a second fixed contact member side of the movable contact bridge member.

According to one embodiment the second reverse-blocking semiconductor device is connectable to the movable contact bridge member by arcing. According to one embodiment the movable contact bridge member has a second portion galvanically connectable to the second fixed contact member, wherein the second reverse-blocking semiconductor device has a second leg, which second leg in the open state of the AC contactor extends towards the second portion of the movable contact bridge member to enable arcing between the second leg and the second portion of the movable contact bridge member.

According to one embodiment the second reverse-blocking semiconductor device is galvanically connected to the movable contact bridge member. According to one embodiment the second reverse-blocking semiconductor device is mechanically connected to the movable contact bridge member by means of a second flexible conductor.

According to one embodiment the first reverse-blocking semiconductor device and the second reverse-blocking semiconductor device are connected in anti-parallel to enable current flow in opposite directions.

According to one embodiment the AC contactor is a low voltage AC contactor. With low voltage is here mean voltages up to 1000 V. It should however be noted that the AC contactor may be utilised for higher voltages too, e.g. to medium voltage applications. According to one embodiment the first reverse-blocking semiconductor device is a first diode.

According to one embodiment the second reverse-blocking semiconductor device is a second diode.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, etc., unless explicitly stated otherwise. BRIEF DESCRIPTION OF THE DRAWINGS

The specific embodiments of the inventive concept will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. la schematically shows an AC contactor; Fig. lb schematically shows a first example of an AC contactor;

Fig. lc schematically shows a second example of an AC contactor;

Figs 2a-2d schematically shows the operation of the AC contactor in Fig. lb;

Fig. 3a schematically shows a third example of an AC contactor; and

Figs 3b-c schematically show a fourth example of an AC contactor. DETAILED DESCRIPTION

The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplifying

embodiments are shown. The inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description.

The concept disclosed herein relates to an AC contactor comprising a first fixed contact member, a second fixed contact member and a movable contact bridge member. The movable contact bridge member is arranged to be actuated between a closed contact position in which the movable contact bridge member is in mechanical contact simultaneously with the first fixed contact member and with the second fixed contact member, and in which first position the AC contactor is in a closed state, and open positions in which the AC contactor is in an open state. In the open positions the movable contact bridge member is distanced from the first fixed contact member and the second fixed contact member, and is thus in this case not in mechanical contact with these components.

The AC contactor furthermore comprises a first reverse-blocking

semiconductor device arranged to provide a current path in the forward direction, in the open state of the AC contactor, from the first fixed contact member to the movable contact bridge member. The first reverse-blocking semiconductor device may for example be a first diode or a first thyristor. The AC contactor may optionally comprise a second reverse-blocking

semiconductor device which provides a current path in the forward direction, in the open state of the AC contactor, from the second fixed contact member to the movable contact bridge member. The second reverse-blocking semiconductor device may for example be a second diode or a second thyristor. Each electrical phase of the AC contactor includes a respective arrangement of the type described above. Fig. la shows an example of an AC contactor 1. For simplicity, only part of the interior of the AC contactor is shown in Fig. la. This also applies to the figures that follow. In general, all of the AC contactors presented herein comprise a housing, and means for actuating the movable contact bridge member of each electrical phase by means of a control circuit. AC contactor 1 comprises a first fixed contact member 3a, a second fixed contact member 3b, a movable contact bridge member 5, and a first reverse- blocking semiconductor device 7. The movable contact bridge member 5 is mechanically connectable to the first fixed contact member 3a and the second fixed contact member 3b simultaneously. This is illustrated by the closed contact position A in Fig. la. Hereto, the movable contact bridge member 5 has a first portion 5a that is mechanically connectable to the first fixed contact member 3a and a second portion 5b mechanically connectable to the second fixed contact member 5b. The movable contact bridge member 5 is furthermore movable away from the first fixed contact member 3a and the second fixed contact member 3b, as illustrated by the movable contact bridge member 5' with dashed lines in an open position B. The first fixed contact member 3a and the second fixed contact member 3b are connectable to electrical components such that a closed electrical circuit may be formed when the movable contact bridge member is in the closed contact position A. To this end, each of the first fixed contact member 3a, the second fixed contact member 3b, and the movable contact bridge member 5 are electrodes made of electrically conducting material. They may for example comprise at least one of copper, silver and aluminium.

The first reverse-blocking semiconductor device 7 has a forward direction in which it conducts current and a reverse direction in which it blocks currents up to a pre-specific reverse voltage magnitude. The reverse-blocking semiconductor device voltage and current rating is selected based on the application and the power rating of the AC contactor in question. The first reverse-blocking semiconductor device 7 is arranged to provide a current path 9, in the forward direction, from the first fixed contact member 3a to the movable contact bridge member 5, as schematically illustrated by the dashed line.

The first reverse-blocking semiconductor device 7 is mounted onto the first fixed contact member 3a. Moreover, the first reverse-blocking semiconductor device 7 is preferably located beside the movable contact bridge member 5 at a first fixed contact member side of the movable contact bridge member 5. The first reverse-blocking semiconductor device 7 is hence preferably located on the same side, with respect to the movable contact bridge member 5, as the first fixed contact member 3a.

Fig. lb shows a first example of an AC contactor implementing the current path 9 in Fig. la by means of the first reverse-blocking semiconductor device. AC contactor 1-1 comprises the first fixed contact member 3a, the second fixed contact member 3b and the movable contact bridge member 5, as described above. The first reverse-blocking semiconductor device 7 is connectable to the movable contact bridge member 5 by arcing thereby providing the current path 9. To this end, the first reverse-blocking semiconductor device 7 has a first leg 11 which is bent towards the movable contact bridge member 5. In particular, the first leg 11 is arranged such that in the open state of the AC contactor, the first leg 11 extends towards the first portion 5a of the movable contact bridge member 5 to enable arcing between the first leg 11 and the first portion 5a of the movable contact bridge member 5. This arrangement provides a coupling between the first leg 11 and the movable contact bridge member 5 when the movable contact bridge member 5 has been moved sufficiently far from the first fixed contact member 3a and the second fixed contact member 3b and sufficiently close to the first leg 11 to enable arcing between the first leg 11 and the movable contact bridge member 5.

Fig. lc shows a second example of an AC contactor. AC contactor 1-2 presents another example of implementation of the current path 9 shown in Fig. la. To this end, AC contactor 1-2 comprises the first fixed contact member 3a, the second fixed contact member 3b and the movable contact bridge member 5, as already described above. The AC contactor 1-2 comprises a first flexible conductor 13 connected between the first reverse-blocking semiconductor device 7 and the movable contact bridge member 5 thereby providing the current path 9 shown in Fig. la. Faster commutation of the current to the first reverse-blocking semiconductor device may be obtained than with the coupling described above. With a flexible conductor is here meant a conductor that is sufficiently flexible and bendable that it can flex upon movement of the movable contact bridge member 5, without breaking after a great plurality of actuations of the movable contact bridge member 5 and essentially without affecting actuation of the movable contact bridge member 5·

With reference to Figs 2a-2d the operation of the AC contactor 1-1 will now be described in more detail. The same general principle also applies to operation of the AC contactor 1-2, except that in that case there is a galvanic connection between the first reverse-blocking semiconductor device 7 and the movable contact bridge member 5 instead of a connection where the gap is bridged by an arc. According to the example illustrated in Figs 2a-2d it is assumed that initially, that when the galvanic connection between the movable contact bridge member 5 and the first fixed contact member 3a and the second fixed contact member 3b is broken the current i is flowing from right to left, i.e. from the second fixed contact member 3b towards the first movable contact 3a. This example results in a somewhat slower current commutation into the first reverse-blocking semiconductor device 7, and thus a somewhat slower arc extinguishing, than if the current would be flowing from the left to the right when the movable contact bridge member 5 is opened. In Fig. 2a the movable contact bridge member 5 has been actuated and is in an open position, and is thus not in galvanic contact with any of the first fixed contact member 3a and the second fixed contact member 3b. An arc 15 is present between the movable contact bridge member 5 and the second fixed contact member 3b, and another arc 17 is present between the movable contact bridge member 5 and the first fixed contact member 3a.

In Fig. 2b the movable contact bridge member 5 has been moved further away from the first fixed contact member 3a and from the second fixed contact member 3b than in Fig. 2a, and a connection between the first reverse-blocking semiconductor device 7, and in particular between the first leg 11, and the movable contact bridge member 5 is thereby made possible.

In Fig. 2c, the current i has changed direction, and flows through the first reverse-blocking semiconductor device 7 and to the movable contact bridge member 5 via an arc 19. The current furthermore flows from the movable contact bridge member 5 to the second fixed contact member 3b via arc 21 because the volume of air between the movable contact bridge member 5 and the second fixed contact member 3b is still in a conducting state as a result of the previous arc 15.

In Fig. 2d, the current i has once again changed direction and flows from the second fixed contact member 3b to the movable contact via arc 23. No current will however flow from the movable contact bridge member 5 to the first movable contact 3a. The cause of this is that the first reverse-blocking semiconductor device 7 does not allow current to flow in the reverse direction and no arc will ignite between the movable contact bridge member 5 and the first fixed contact member 3a because no arc has been present here since the situation in Fig. 2b, and thus the air has recovered and does no longer possess the required characteristics for electrical breakdown to occur. To this end, the circuit is now broken and also arc 23 is extinguished, and no current will flow through the AC contactor 1-1 until the movable contact bridge member 5 is moved to the closed contact position again. In case the current i would have been flowing to the right in Fig. 2a, an arc would first occur between the first fixed contact member 3a and the movable contact bridge member 5. When the movable contact bridge member 5 has been connected by arcing to the first reverse-blocking semiconductor device 7 the current would be commutated to the first reverse-blocking semiconductor device 7 and the situation in Fig. 2c would be obtained, followed by the state shown in Fig. 2d.

Figs 3a and 3b show additional examples of AC contactors. The idea is based on replacing the two arc splitters in each phase in a conventional AC contactor with reverse-blocking semiconductor devices. The reverse-blocking semiconductor devices should be anti-parallel to make sure that one of the reverse-blocking semiconductor devices will be conducting when the movable contact bridge member opens and creates two arcs in series in order to commutate the current from one of the arcs to the conducting reverse- blocking semiconductor device and then at next current zero interrupt the current. During the reverse-blocking semiconductor device conduction time the contact gap will recover and get a high voltage withstand. At the coming current zero crossing the reverse-blocking semiconductor device will interrupt the current and the reverse-blocking semiconductor device will take up the recovery voltage. Fig. 3a shows an example of an AC contactor comprising two reverse- blocking semiconductor devices. AC contactor 1-3 comprises the first fixed contact member 3a, the second fixed contact member 3b, the movable contact bridge member 5, and the first reverse-blocking semiconductor device 7 in the same manner as the example shown in Fig. lb. In addition, AC contactor 1-3 comprises a second reverse-blocking semiconductor device 25 which is connected in antiparallel with the first reverse-blocking

semiconductor device 7. The second reverse-blocking semiconductor device 25 is arranged to provide a current path 9, in the forward direction, from the second fixed contact member 3b to the movable contact bridge member 5.

The second reverse-blocking semiconductor device 25 is mounted onto the second fixed contact member 3b. Moreover, the second reverse-blocking semiconductor device 25 is preferably located beside the movable contact bridge member 5 at a second fixed contact member side of the movable contact bridge member 5. The second reverse-blocking semiconductor device 25 is hence preferably located on the same side, with respect to the movable contact bridge member 5, as the second fixed contact member 3b.

According to the example in Fig. 3a, the first reverse-blocking semiconductor device 7 has the first leg 11, and the second reverse-blocking semiconductor device 25 has a second leg 27. The second leg 27 is bent towards the movable contact bridge member 5. In particular, the second leg 27 is arranged such that in the open state of the AC contactor, the second leg 27 extends towards the second portion 5b of the movable contact bridge member 5 to enable arcing between the second leg 27 and the second portion 5b of the movable contact bridge member 5. This arrangement provides a coupling between the second leg 27 and the movable contact bridge member 5 when the movable contact bridge member 5 has been moved sufficiently far from the first fixed contact member 3a and the second fixed contact member 3b and as a result sufficiently close to the second leg 27 to enable arcing between the second leg 27 and the movable contact bridge member 5. The second reverse-blocking semiconductor device 25 is hence according to the example in Fig. 3a connectable to the movable contact bridge member 5. Fig. 3b shows another example of an AC contactor comprising the first reverse-blocking semiconductor device 7 and the second reverse-blocking semiconductor device 25. This example is similar to the example shown in Fig. lc, except that it has two reverse-blocking semiconductor devices and two flexible conductors. In particular, the first reverse-blocking

semiconductor device 7 is mechanically connected to the movable contact bridge member 5 by means of the first flexible conductor 13, while the second reverse-blocking semiconductor device 25 is mechanically connected to the movable contact bridge member 5 by means of a second flexible conductor 29. Fig. 3c shows the AC contactor when the movable contact bridge member 5 has been moved away from the first fixed contact member 3a and the second fixed contact member 3b.

The operation of AC contactors 1-3 and 1-4 is similar to what has been described above, except that the two reverse-blocking semiconductor devices provide for faster current commutation, because commutation will be provided irrespective of the current direction at the time when mechanical contact between the movable contact bridge member 5 and first fixed contact member 3a and the second fixed contact member 3b is broken.

Although more expensive than diodes, thyristors may be advantageous compared to diodes in that their conductive state may be controlled via its gate so that in the presence of large currents e.g. short circuit currents, a thyristor may be left in a non-conducting state even when forward biased. A reverse-blocking semiconductor device in the form of a thyristor may thereby be protected from damage in such situations. The inventive concept has mainly been described above with reference to a few examples. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.

Claims

1. An alternating current, AC, contactor (1; 1-1; 1-2; 1-3; 1-4), comprising: a first fixed contact member (3a), a second fixed contact member (3b),

5 a movable contact bridge member (5) mechanically connectable to the first fixed contact member (3a) and to the second fixed contact member (3b) simultaneously to allow current (i) to flow between the first fixed contact member (3a) and the second fixed contact member (3b), and which movable contact bridge member (5) is arranged to be moved away from the first fixed 0 contact member (3a) and the second fixed contact member (3b) to obtain an open state of the AC contactor (1; 1-1; 1-2; 1-3; 1-4), and a first reverse-blocking semiconductor device (7) arranged to provide a current path (9) in the forward direction of the first reverse-blocking semiconductor device (7), in the open state of the AC contactor (1; 1-1; 1-2; 1- !5 3; ^1-4), from the first fixed contact member (3a) to the movable contact

bridge member (5).

2. The AC contactor (1; 1-1; 1-2; 1-3; 1-4) as claimed in claim 1, wherein the first reverse-blocking semiconductor device (7) is mounted onto the first fixed contact member (3a) and located beside the movable contact bridge 0 member (5) at a first fixed contact member side of the movable contact

bridge member (5).

3. The AC contactor (1; 1-1; 1-3) as claimed in claim 1 or 2, wherein the first reverse-blocking semiconductor device is connectable to the movable contact bridge member by arcing. 5

4. The AC contactor (1; 1-1; 1-3) as claimed in claim 3, wherein the movable contact bridge member (5) has a first portion (5a) galvanically connectable to the first fixed contact member (3a), and wherein the first reverse-blocking semiconductor device (7) has a first leg (11), which first leg (11) in the open state of the AC contactor extends towards the first portion (5a) of the movable contact bridge member (5) to enable arcing between the first leg (11) and the first portion (5a) of the movable contact bridge member (5).

5. The AC contactor (1; 1-2; 1-4) as claimed in claim 1 or 2, wherein the first reverse-blocking semiconductor device (7) is galvanically connected to the movable contact bridge member (5).

6. The AC contactor (1; 1-2; 1-4) as claimed in claim 5, wherein the first reverse-blocking semiconductor device (7) is galvanically connected to the movable contact bridge member (5) by means of a first flexible conductor (13).

7. The AC contactor (1; 1-3; 1-4) as claimed in any of the preceding claims, comprising a second reverse-blocking semiconductor device (25) arranged to provide a current path in the forward direction of the second reverse- blocking semiconductor device (25), in the open state of the AC contactor, from the second fixed contact member (3) to the movable contact bridge member (5), which first reverse-blocking semiconductor device (7) and second reverse-blocking semiconductor device (25) are connected in antiparallel.

8. The AC contactor (1; 1-3; 1-4) as claimed in claim 7, wherein the second reverse-blocking semiconductor device (7) is mounted onto the second fixed contact member (3b) and located beside the movable contact bridge member (5) at a second fixed contact member side of the movable contact bridge member (5).

9. The AC contactor (1; 1-3) as claimed in claim 7 or 8, wherein the second reverse-blocking semiconductor device (25) is connectable to the movable contact bridge member by arcing (5).

10. The AC contactor (1; 1-3) as claimed in claim 9, wherein the movable contact bridge member (5) has a second portion (5b) galvanically connectable to the second fixed contact member (3b), wherein the second reverse- blocking semiconductor device (25) has a second leg (27), which second leg (27) in the open state of the AC contactor extends towards the second portion (5b) of the movable contact bridge member (5) to enable arcing between the second leg (27) and the second portion (5b) of the movable contact bridge member (5).

11. The AC contactor (1; 1-4) as claimed in claim 7 or 8, wherein the second reverse-blocking semiconductor device (25) is galvanically connected to the movable contact bridge member (5).

12. The AC contactor (1; 1-4) as claimed in claim 11, wherein the second reverse-blocking semiconductor device (25) is galvanically connected to the movable contact bridge member (5) by means of a second flexible conductor (29).

13. The AC contactor (1; 1-3; 1-4) as claimed in any of claims 7-12, wherein the first reverse-blocking semiconductor device (7) and the second reverse- blocking semiconductor device (25) are connected in anti-parallel to enable current flow in opposite directions.

14. The AC contactor (1; 1-1; 1-2; 1-3; 1-4) as claimed in any of the preceding claims, wherein the first reverse-blocking semiconductor device (7) is a first diode.

15. The AC contactor (1; 1-1; 1-2; 1-3; 1-4) as claimed in any of claims 7-14, wherein the second reverse-blocking semiconductor device (25) is a second diode.

16. The AC contactor (1; 1-1; 1-2; 1-3; 1-4) as claimed in any of the preceding claims, wherein the AC contactor is a low voltage AC contactor.