Direct-current contactor with additional switching capability for AC loads and a polarity against the preferential current direction

Abstract

Disclosed is a DC contactor comprising a double break with two contact points, each having a fixed and a movable contact, the movable contacts arranged on a contact bridge. The contactor includes an arc extinguishing device and a blowing device configured to blow a switch arc, which forms at the first contact point when the contact points are being opened, into the arc extinguishing device, when switching takes place in the preferential current direction. A commutating plate is arranged adjacent the movable contact of the first contact point, the contact bridge and the commutating plate being electrically insulated from one another and the commutating plate being potentially connected to the fixed contact of the second contact point, so that, when switching takes place in the preferential current direction, the switch arc forming at the first contact point jumps from the contact bridge to the commutating plate by the blowing device.

Claims

1. A direct-current contactor with preferential current direction, comprising a double break with two contact points, which each comprise a fixed contact and a movable contact, the movable contacts being arranged on a contact bridge, and further comprising an electric arc extinguishing device as well as a blowing device, said blowing device being configured to blow a switch arc, which forms at the first contact point when the contact points are being opened, into the electric arc extinguishing device, when switching takes place in the preferential current direction, wherein a commutating plate is arranged adjacent the movable contact of the first contact point , wherein the contact bridge and the commutating plate are electrically insulated from one another, and wherein the commutating plate is potentially connected to the fixed contact of the second contact point, so that, when switching takes place in the preferential current direction, the switch arc forming at the first contact point jumps from the contact bridge to the commutating plate due to the effect produced by the blowing device thus bridging the switch arc formed at the second contact point, wherein the direct-current contactor comprises an auxiliary electric arc extinguishing device , the blowing device being dimensioned and configured such that, due to the effect produced by the blowing device, the switch arc forming at the first contact point jumps, when switching takes place in a direction opposite to the preferential current direction, from the contact bridge to the fixed contact of the second contact point and is caused to pass between the two fixed contacts and into the auxiliary electric arc extinguishing device by means of blowing; and wherein the auxiliary electric arc extinguishing device is arranged between two contact rails, which connect the two fixed contacts to connecting contacts of the direct-current contactor.

2. The direct-current contactor according to claim 1, wherein the auxiliary electric arc extinguishing device is dimensioned such that it is smaller than the electric arc extinguishing device.

3. The direct-current contactor according to claim 1, wherein the electric arc extinguishing device and/or the auxiliary electric arc extinguishing device comprise a plurality of extinguishing elements made of ceramics.

4. The direct-current contactor according to claim 3, wherein flow passages are formed between the extinguishing elements, said flow passages being each provided with a dispersing portion, the dispersing portions of neighboring flow passages being configured such that they have different inclinations, so that the gases discharged from the extinguishing elements will be fanned out.

5. The direct-current contactor according to claim 1, wherein the contact bridge narrows at an end facing the commutating plate.

6. The direct-current contactor according to claim 1, wherein the blowing device includes a permanent magnet disposed adjacent to an end of the contact bridge, a ceramic protection element being arranged between the permanent magnet and the end of the contact bridge.

7. The direct-current contactor according to claim 1, wherein the commutating plate is covered, at least partially, by a shield element on an outer side facing away from the electric arc extinguishing device.

8. The direct-current contactor according to claim 1, wherein the contact points and the commutating plate are insulated, at least in certain areas thereof, from a drive and/or a control unit of the direct-current contactor by means of an insulating foil.

9. The direct-current contactor according to claim 8, wherein a protective cover is arranged between the insulating foil and the second contact point.

Description

(1) In the following, an advantageous embodiment of the present invention will be explained in more detail making reference to drawings, in which:

(2) FIG. 1 shows an oblique view of a direct-current contactor according to the present invention,

(3) FIG. 2 shows the direct-current contactor according to the present invention according to FIG. 1 in a partially open condition of the housing, and

(4) FIG. 3 shows a detail view of one of the extinguishing elements of the direct-current contactor according to the present invention according to FIGS. 1 and 2.

(5) In the statements following hereinbelow like parts are designated by like reference numerals. If a drawing comprises reference numerals which are not discussed in detail in the associated description of the figure, reference is made to preceding or subsequent descriptions of figures.

(6) An oblique view of a direct-current contactor 1 according to the present invention is shown in FIG. 1. The interior structural design of the direct-current contactor 1 is shown in FIG. 2. The direct-current contactor 1 includes a double break with two contact points 2 and 3. The first contact point consists of a fixed contact 4 and a movable contact 5, the second contact point 3 comprises a fixed contact 6 and an associated movable contact 7. The two movable contacts 5 and 7 are arranged on a contact bridge 8. The contact bridge 8 is actuated by an electromagnetic drive 25 that is controlled by means of the control unit 23. The control unit 23 is here arranged outside of the housing 31 of the direct-current contactor 1 according to the present invention and is therefore also visible in FIG. 1. Each of the two fixed contacts 4 and 6 is connected to a respective connecting contact 27 of the direct-current contactor via a contact rail 14 and 15, respectively.

(7) When the contact points are opened, a switch arc forms, which must be extinguished as quickly as possible so as to avoid damage to the contacts or other components of the direct-current contactor. To this end, the direct-current contactor 1 is provided with an electric arc extinguishing device 9 as well as a blow device 10 consisting essentially of a permanent magnet. The magnetic field of the permanent magnet 10 is oriented such that a switch arc forming at the first contact point 2 when there is a flow of current in the preferential current direction is driven into the electric arc extinguishing device 9. In order to ensure that the magnetic field is built up at the decisive points, suitable pole plates 30, which are known from the prior art, are arranged on both sides of the housing. One of the two pole plates is shown in FIG. 1.

(8) The direct-current contactor 1 according to the present invention is provided with a so-called commutating plate 11, which begins close to the first contact point 2 and which abuts in a clamplike manner on the left boundary area of the electric arc extinguishing device 9. Via a connecting wire 12, the commutating plate 11 is potentially connected to the fixed contact 6 of the second contact point. When there is a flow of current in the preferential direction, the switch arc forming at the first contact point jumps, due to the effect produced by the magnetic field, from the contact bridge 8 to the commutating plate 11, thus bridging the switch arc that forms at the second contact point. The commutating plate 11 and the contact rail 14 connected to the first fixed contact 4 then act as electric arc deflectors. By means of these electric arc deflectors, the switch arc forming at the first contact point 2 is stretched while it is being blown into the electric arc extinguishing device 9 by the permanent magnet 10. Fast and reliable extinguishing of the switch arc is accomplished in this way.

(9) In order to support the switch arc in jumping from the contact bridge 8 to the commutating plate 11, the contact bridge end 20 located at the contact point 2 is configured such that it tapers. For preventing the switch arc from striking through from the contact bridge 8 to the permanent magnet 10 arranged adjacent thereto, a platelike ceramic protection element 21 is disposed between the end 20 of the contact bridge 8 and the permanent magnet 10.

(10) When the fixed contacts of the direct-current contactor according to the present invention have applied thereto a voltage poled in a direction opposite to the preferential direction, the switch arc forming at the first contact point 2 cannot be extinguished by the electric arc extinguishing device 9. In this case, the magnetic field of the permanent magnet 10 ensures that the switch arc forming at the first contact point 2 will be blown downwards away from the electric arc extinguishing device 9. For guaranteeing a reliable extinction of the switch arc also in this case, the direct-current contactor according to the present invention is provided with an auxiliary electric arc extinguishing device 13. This device 13 is located between the two contact rails 14 and 15 of the two fixed contacts 4 and 6. Due to the effect produced by the magnetic field, the switch arc forming at the first contact point 2 is driven along the contact bridge 8 from the movable contact 5 of the first contact point in the direction of the movable contact 7 of the second contact point and, in the course of this process, it jumps to the neighboring fixed contact 6 of the second contact point and merges with the switch arc forming at the second contact point 3. The switch arc forming at the second contact point 3 is extinguished in any case as soon as the switch arc forming at the first contact point jumps from the contact bridge 8 to the fixed contact 6 of the second contact point 3. From this moment onwards, the two contact rails 14 and 15 act as electric arc deflectors. Through the blowing effect produced by the permanent magnet 10, the switch arc is driven along these two electric arc deflectors into the auxiliary electric arc extinguishing device 13 where it is extinguished. Hence, the direct-current contactor according to the present invention is also suitable for switching off currents flowing in a direction opposite to the preferential direction and AC loads safely and reliably up to a certain level. For achieving a compact structural design, the contact points and the commutating plate are insulated from the drive unit and the control unit by an insulating foil 24. In order to prevent the insulating foil from burning off in the area of the second contact point 3 due to the switch arc forming at the contact point 3, said insulating foil 24 is, in this area, covered by a protective cover in the form of a small steel plate 26. In order to protect the control unit 23 against parasitic influences, a shield element 22 is disposed between the control unit 23 and the commutating plate 11 and the electric arc extinguishing device 9, respectively.

(11) Both the electric arc extinguishing device 9 and the auxiliary electric arc extinguishing device 13 consist of a plurality of ceramic extinguishing elements 16. One of the extinguishing elements is shown in detail in FIG. 3. As can clearly be seen from FIG. 3, two respective neighboring extinguishing elements have formed between them a flow passage 17 through which the plasma generated by the switch arc is conducted to the outside. Towards the discharge end 19, the flow passage includes a dispersing portion 18, the dispersing portions of neighboring flow passages being configured such that they have different inclinations, so that the gases discharged from the extinguishing elements will be fanned out. The plasma generated by the switch arc can be removed more quickly in this way, and also the switch arc can thus be extinguished within a shorter period of time.

(12) For the purpose of maintenance and inspection, some of the extinguishing elements of the electric arc extinguishing device 9 may be removed, without it being necessary to disassemble the housing 31 of the direct-current contactor according to the present invention. The removable extinguishing elements are combined by means of the clips 28 shown in FIGS. 1 and 2 so as to form a removable insert. The latter can be locked and unlocked by means of the latch 29 shown in FIG. 1. The insert comprises the extinguishing elements through which the first contact point 2 is concealed. By removing the insert, the contacts can adequately be checked.