WO1995011513A1

WO1995011513A1 - Diverter switch

Info

Publication number: WO1995011513A1
Application number: PCT/SE1994/000984
Authority: WO
Inventors: Sivert Norman
Original assignee: Asea Brown Boveri Ab
Priority date: 1993-10-20
Filing date: 1994-10-19
Publication date: 1995-04-27
Also published as: SE9303448L; SE501930C2; SE9303448D0

Abstract

The invention relates to a diverter switch which is intended to be part of an on-load tap changer for transformers. The diverter switch is provided with main contacts (10-13), arcing contacts (14-17) and resistor contacts (18-20). The movable parts (11-13, 15, 17) of the main and arcing contacts are arranged on a contact carrier (35) which is rotatable back and forth and operated by a central axle (34). In addition, the contact carrier is provided with one arm (19) per phase which, in addition to operating the resistor contacts (18-20), also constitutes one of the contact members thereof. The correct contact sequence when switching between different winding terminals is achieved by the location of contacts (10-20) and stop members (38, 39, 43).

Description

Diverter switch

The present invention relates to a diverter switch of the kind described in the preamble to claim 1. The diverter switch is intended to form together with a tap selector an on-load tap changer for transformers.

In prior art diverter switches, relatively complicated devices are required for operating the contacts to achieve contact opening and contact closing in the proper sequence. In an embodiment of a three-phase cylindrical diverter switch described in DE-B-2535114, the operation has admittedly been simplified but this has instead resulted in other drawbacks. Thus, in the design described therein the load current has to pass two series-connected sliding contacts at the periphery of the diverter switch, which either entails an increase of the dimensions of the diverter switch or a considerable limitation of the current-carrying capacity of the diverter switch.

The object of the present invention is to obtain a diverter switch with a contact system which is simple to operate and which can be designed, in a simple manner, for relatively high rated current. In addition, the design should have relatively small external dimensions and exhibit a large ratio between the contact distance and the diameter of the contact assembly. This is achieved according to the inven¬ tion by a diverter switch with the characteristic features described in claim 1.

In a diverter switch according to the invention, in which the arcing contacts are located along the periphery of the switch, large contact distances in relation to the diameter of the switch are obtained, which entails relatively high performance with respect to breaking capacity and voltage withstand capability. Since the contact carrier for the movable parts of the main and arcing contacts is also adapted to operate the resistor contacts and, in addition, to constitute part thereof, the desired contact sequence is achieved with one single movable contact carrier system, which makes the design exceedingly simple and reliable with few movable parts. Another important advantage with the proposed design is that the contact assembly may be extended in the vertical direction to achieve a higher rated current. For example, diverter switches for a rated current of 1500 A may be designed in accordance with this principle.

The invention will be explained in greater detail by describing an embodiment with reference to the accompanying drawings, wherein

Figure 1 shows an axial view of the contact system in a three-phase diverter switch according to the invention, parts of the system being omitted to render the figure clearer,

Figure 2 shows in greatly simplified form a side view of the contact system according to Figure 1, and

Figures 3a-3f show the contact positions in one phase at different times during a switching operation between two terminals of a transformer winding.

The diverter switch shown in Figures 1 and 2 is cylindri- cally constructed with three identical sectors A, B and C, the contact systems of which may, for example, each be connected into a respective phase of a three-phase trans- former. For the sake of clarity, sector A only shows the current contacts in the operating position, sector B only the resistor contacts in the operating position, and sector C both the current and resistor contacts during a tap-change operation.

The diverter switch has a stand which comprises a circular stand plate 30 (Fig. 2), which by means of three insulating supports 31, arranged at the periphery, is secured to a plate 32 of insulating material. At its periphery, the stand plate 30 supports, via insulating supports 33, two fixed main contact members 10, 12 per phase, which are arranged in spaced relationship to each other and are provided with connection members to be connected, via a tap selector, to terminals on a transformer winding. In close proximity to the fixed main contact members 10, 12, two fixed arcing con¬ tact members 14, 16 are arranged.

In the centre of the plate 30, an axle 34 is connected to a contact carrier 35 and is rotatable back and forth between two operating contact positions. The angle of rotation in the example shown is about 40°. The contact carrier 35 supports two movable main contact members 11, 13 per phase, which are arranged to cooperate with the fixed main contact members 10, 12, and two movable arcing contact members 15, 17 per phase, arranged to cooperate with the fixed arcing contact members 14, 16. The movable main contact members 11, 13 are secured to the contact carrier 35. The movable arcing contact members 15, 17 consist of arms which are rotatably journalled around axes 36 on the contact carrier 35 and which, through tension springs 37, are constantly influenced by forces in a direction towards stop lugs 38, 39 arranged on the contact carrier. As is shown in Figure 1 (where only one of these springs is shown) , each such spring 37 extends from a movable arcing contact member in one phase to the nearest arcing contact member in the adjacent phase. All arcing contact members may, for example, be provided with contact ferrules of copper-tungsten.

Via a current collector 40 making contact with the central part of the contact carrier 35, the contact carrier is connected to an external connection member for, for example, neutral terminal connection.

The diverter switch is provided with two resistor contact members 18, 20 per phase. These consist of arms which are rotatably journalled around shaft stubs 41 secured to the insulating plate 32. The resistor contact members 18, 20, which are each connected together in series with a transi¬ tion resistor 22, 23 (Fig. 3), are each connected to a tension spring 42 (Fig. 1), which influences the respective resistor contact member with a force in a direction towards a stop member 43 positioned between the two contact members and secured to the insulating plate 32. This stop member may, for example, be in the form of two pins arranged spaced from each other (as shown in sector B in Fig. 1) or one single stub integrated with the plate 32 (as shown in sector C in Figure 1) .

The contact carrier 35 connected to the axle 34 is provided with one arm 19 per phase which extends radially out towards the periphery of the switch. The arm 19 is provided with an end portion, which extends through a recess 44 at the peri¬ phery of the insulating plate 32 and between the two resis¬ tor contact members 18, 20. This arm 19 has two different functions. In addition to the arm transferring operating power to the rotatably journalled resistor contact members, it constitutes the necessary counter-contact member thereto. The resistor contact members 18, 20 and the outer end portion of the arm 19 may, for example, be provided with contact ferrules of copper-tungsten.

For operating the contact system, the diverter switch is provided with an operating device which is connected to the axle 34.

Figures 3a-3f show the switching process in one phase when switching from a terminal 1 to a terminal 2 on a transformer winding 3.

Figure 3a shows the diverter switch in operating position 1. The load current passes through the main contact 10, 11, the contact carrier 35 and the current collector 40. The left- hand arcing contact 14, 15 and the lefthand resistor contact 18, 19 are closed. In Figure 3b the main contact 10, 11 has opened. The load current passes through the lefthand arcing contact 14, 15.

In Figure 3c the lefthand arcing contact 14, 15 has opened. Also the righthand resistor contact 19, 20 has now closed, and the load current is divided between the resistor con¬ tacts 18, 19 and 19, 20. A circulation current flows through the bridged part of the transformer winding but is limited by the transition resistors 22, 23.

In Figure 3d the lefthand resistor contacts 18, 19 have opened (because of the stop member 43). The load current passes through the righthand resistor contact 19, 20 and the resistor 23.

In Figure 3e the righthand arcing contact 16, 17 has closed, and the load current passes therethrough.

In Figure 3f also the righthand main contact 12, 13 has closed, and operating position 2 is obtained.

The invention is not limited to the embodiment shown, but several variants are possible within the scope of the invention. For example, the invention may also be used in diverter switches of single-phase design and in diverter switches intended for other use than at the neutral point of a transformer winding. Further, the axle 34 of the diverter switch need not necessarily be vertically oriented, but may also be oriented horizontally.

Claims

1. A diverter switch comprising

- two fixed main contact members (10, 12) arranged in spaced relationship to each other along a circular orbit,

- two movable main contact members (11, 13) which are arranged for cooperation with the fixed main contact members (10, 12) and which are supported by a contact carrier (35) connected to a rotatable central axle (34),

- two fixed arcing contact members (14, 16) arranged adjacent to the fixed main contact members,

two movable arcing contact members (15, 17) which are arranged for cooperation with the fixed arcing contact members (14, 16) and which are supported by said rotatable contact carriers (35),

- two resistor contact members (18, 20) arranged spaced from each other and rotatably journalled in a stationary plate (32) of insulating material, said resistor contact members being each connected in series with a transition resistor (22, 23),

characterized in that said rotatable contact carriers (35) are provided with an arm (19) which serves as a counter-contact member to said rotatably journalled resistor contact members (18, 20) and which serves as operating member for the same contact members (18, 20) .

2. A diverter switch according to claim 1, characterized in that said movable arcing contact members (15, 17) are rotatably journalled in said rotatable contact carrier (35) and are urged by resilient members (37) in a direction towards stop members (38, 39) arranged on the contact carrier (35) .

3. A diverter switch according to claim 1 or 2, characterized in that said rotatably journalled resistor contact members (18, 20) are urged by resilient members (42) in a direction towards a stop member (43) arranged between the two contact members and secured to said insulating plate (32) .

4. A diverter switch according to claim 2 or 3, characterized in that said resilient members (37) for influencing the movable arcing contact members (15, 17) consist of tension springs, each of which extends from a movable arcing contact member in one pole to the nearest movable arcing contact member in the adjacent pole.

5. A diverter switch according to any of the preceding claims, characterized in that said insulating material plate (32) forms a partition between, on the one hand, said rotatable contact carrier (35) with the movable main and arcing contact members (11, 13 and 15, 17, respectively) and, on the other hand, the rotatably journalled resistor contact members (18, 20) .