EP4276864A1

EP4276864A1 - Vacuum interrupter

Info

Publication number: EP4276864A1
Application number: EP22172209.3A
Authority: EP
Inventors: Christian Reuber; Dietmar Gentsch; Kai Gorlt; Thomas Schmoelzer
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2022-05-08
Filing date: 2022-05-08
Publication date: 2023-11-15
Also published as: CN117038384A

Abstract

The present invention relates to a vacuum interrupter, comprising:
- a first carrier (101); and
- a second carrier (102);
wherein the first carrier comprises a stem (10) and a contact piece (1);
wherein the second carrier comprises a stem (10) and a contact piece (1);
wherein the contact piece of the first carrier comprises a first contact part (30) and a second contact part (20) surrounding the first contact part;
wherein the contact piece of the second carrier comprises a first contact part (30) and a second contact part (20) surrounding the first contact part; and
wherein a material of at least a portion of the first contact part of the first carrier is different to a material of the second contact part of the first carrier; and/or wherein a material of at least a portion of first contact part of the second carrier is different to a material of the second contact part of the second carrier.

Description

FIELD OF THE INVENTION

The present invention relates vacuum interrupters and contact pieces for vacuum interrupters.

BACKGROUND OF THE INVENTION

Vacuum interrupters are required to have contacts that can operate with a high short circuit switching performance and resist becoming welded together.
The material for the contact pieces of vacuum interrupters (Vis) have to fulfil several requirements such as a low resistance in closed position, the ability to interrupt a certain current, the avoidance of welding, and a low chopping current.
Current chopping can occur when a mechanical switch, like a vacuum interrupter, is opening an electrical circuit with a current. In the moment of the mechanical opening, an electrical arc establishes between the contacts and the current continues to flow. Ideally, the current would flow until its next current zero; then the circuit is opened.
It can however happen that the current is cut-off or "chopped" a little bit earlier, at a level of a few Amperes. In a VI, a certain energy is required to keep the arc active; this energy comes from the current. In case the current is low, it can therefore happen that the arc, and so the current, is chopped.
The actual value of a chopping current can vary with each interruption; it is a kind of statistical distribution. Higher values occur with decreasing probability.
If one considers a cable and an electrical motor as a load that is being switched off by a vacuum interrupter, the consequence of the chopped current is that an oscillation starts between the inductance of the motor and the stray capacitance of the cable, using the actual current in the motor as a starting energy. As said stray capacitance is low, the resulting overvoltage will be high and can damage the insulation of the motor windings.
To avoid this damage, the overvoltages can be damped with surge arrestors, which has the drawback of having a separate component (space, costs).
The mean level of current chopping depends on the contact material of the VI, and therefore the material of the contacts can be appropriately chosen. WCAg has a lower level of chopping current compared to CuCr.
CuCr is widely used for Circuit Breakers for its low resistance, its high interrupting capability, and its moderate chopping current. However, the typical chopping current level of CuCr is still relatively high for some applications like small inductive loads, and additional means like the above described surge arrestors have to be provided to eliminate the risk of damaging the load due to chopping current induced overvoltages. Also, CuCr has a certain tendency to weld, but this can be managed with suitable contact pressures and strong drives.
WCAg is widely used for contactors for its low resistance, its sufficient interrupting capability, its low tendency to weld and especially for its very low chopping current. The disadvantage is that this material is not well suited for the market-required extension of the short circuit interrupting capability, and the disadvantage that the Ag in the contacts is expensive.
Also, when contactors are further developed towards higher short circuit interrupting capabilities, it might occur that the limiting factor is not the short circuit interruption itself, but the increase of the resistance of the contact pieces. Under arcing, WCAg contact pieces evaporate some of their silver content. The fact that the silver evaporates relatively easily results in the aimed low chopping current. The corresponding loss of silver in the contact pieces is not critical when switching load currents. However, when short circuit currents are being switched, the loss of silver in the WCAg contact pieces can be meaningful and eventually result in a failed typetest, as the increase of the resistance of the VI during the test is limited by the relevant standards, e.g. IEC 62271-106, 6.102.9
There is a need to address these issues.

SUMMARY OF THE INVENTION

Therefore, it would be advantageous to have an improved vacuum interrupter technology.
The object of the present invention is solved with the subject matter of the independent claims, wherein further embodiments are incorporated in the dependent claims.
In a first aspect, there is provided a vacuum interrupter, comprising:

a first carrier; and
a second carrier.

The first carrier comprises a stem and a contact piece. The second carrier comprises a stem and a contact piece. The contact piece of the first carrier comprises a first contact part and a second contact part surrounding the first contact part. The contact piece of the second carrier comprises a first contact part and a second contact part surrounding the first contact part. A material of at least a portion of the first contact part of the first carrier is different to a material of the second contact part of the first carrier, and/or a material of at least a portion of first contact part of the second carrier is different to a material of the second contact part of the second carrier.
In an example, in a deactivated state the vacuum interrupter is configured to hold the contact piece of the first carrier spaced from the contact piece of the second carrier and in an activated state the vacuum interrupter is configured to bring the contact piece of the first carrier and the contact piece of the second carrier into contact with one another.
In an example, in a deactivated state the vacuum interrupter is configured to hold the contact piece of the first carrier in contact with the contact piece of the second carrier and in an activated state the vacuum interrupter is configured to separate the contact piece of the first carrier from the contact piece of the second carrier.
In an example, the first carrier is a fixed contact carrier and the second carrier is a movable contact carrier, and in the activated state the vacuum interrupter is configured to move the second carrier.
In an example, the first carrier is a movable contact carrier and the second carrier is a fixed contact carrier, and in the activated state the vacuum interrupter is configured to move the first carrier.
In an example, the material of all of the first contact part of the first carrier is different to the material of the second contact part of the first carrier, and/or the material of all of the first contact part of the first carrier is different to the material of the second contact part of the first carrier
In an example, a junction between the first contact part and the second contact part of the contact of the first carrier defines a plane. The first contact part comprises a portion with a surface below the plane and the at least a portion of the first contact part is the remaining portion of the first contact part other than the portion with the surface below the plane.
In an example, a junction between the first contact part and the second contact part of the contact of the second carrier defines a plane. The first contact part comprises a portion with a surface below the plane and the at least a portion of the first contact part is the remaining portion of the first contact part other than the portion with the surface below the plane.
In an example, a junction between the first contact part and the second contact part of the contact of the first carrier defines a plane. The at least a portion of the first contact part comprises a portion with a surface above the plane.
In an example, a junction between the first contact part and the second contact part of the contact of the second carrier defines a plane. The at least a portion of the first contact part comprises a portion with a surface above the plane.
In an example, the material of the second contact part of the first carrier is WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or Cu/C or MoCu/C or Cu or WCu or WCCu or WCCu/C or MoCCu/C or Ag/C or Cu.
In an example, the material of the second contact part of the second carrier is WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or Cu/C or MoCu/C or Cu or WCu or WCCu or WCCu/C or MoCCu/C or Ag/C or Cu.
In an example, the material of the at least a portion of the first contact part of the first carrier is Ag/C or Cu/C or CuCr or CuCr/C or WCu or WCu/C or MoCu/C or Sn/C or C.
In an example, the material of the at least a portion of the first contact part of the second carrier is Ag/C or Cu/C or CuCr or CuCr/C or WCu or WCu/C or MoCu/C or Sn/C or C.
In an example, a junction between the first contact part and the second contact part of the contact of the first carrier defines a plane. The at least a portion of the first contact part is a conical pin that projects outwards from the plane.
In an example, a junction between the first contact part and the second contact part of the contact of the second carrier defines a plane. The at least a portion of the first contact part is a conical pin that projects outwards from the plane.
In an example, the material of the at least a portion of the first contact part of the first carrier is carbon.
In an example, the material of the at least a portion of the first contact part of the first carrier is carbon.
In an example, the second contact part of the first carrier comprises one or more slits.
In an example, the second contact part of the second carrier comprises one or more slits.
In an example, the first contact part of the first carrier comprises one or more slits.
In an example, the first contact part of the second carrier comprises one or more slits.
In an example, the one or more slits in the first contact part of the first carrier are a continuation of the one or more slits in the second contact part of the first carrier.
In an example, the one or more slits in the first contact part of the second carrier are a continuation of the one or more slits in the second contact part of the first carrier.
In an example, the material of the at least a portion of the first contact part of the first carrier is the same as the material of the at least a portion of the first contact part of the second carrier.
In an example, the material of the second contact part of the first carrier is the same as the material of the second contact part of the second carrier.
In an example, a shape of the at least a portion of the first contact part of the first carrier is the same as a shape of the at least a portion of the first contact part of the second carrier.
In an example, a shape of the second contact part of the first carrier is the same as a shape of the second contact part of the second carrier.
In a second aspect, there is provided a vacuum interrupter, comprising:

a first carrier; and
a second carrier.

The first carrier comprises a stem and a contact piece. The second carrier comprises a stem and a contact piece. The contact piece of the first carrier is made from a first material. The contact piece of the second carrier is made from a second material. The following can apply:

The first material is Ag/C and the second material is WCAg or WCAg/C; or
The first material is WCAg/C and the second material is WCAg or WCAg/C; or
The first material is Cu/C and the second material is CuCr or CuCr/C or WCu or WCu/C or Cu; or
The first material is WCu/C and the second material is CuCr or Cu; or
The first material is WCCu/C and the second material is CuCr or CuCr/C or WCu or WCu/C or WCCu/C or Cu; or
The first material is MoCu/C and the second material is WCMo/C or CuCr or CuCr/C or WCu or WCu/C or Cu; or
The first material is MoCCu/C and the second material is CuCr/C or Cu.

In an third aspect, there is provided a contact piece for a vacuum interrupter. The contact piece comprises:

a first contact part; and
a second contact part.

The second contact part surrounds the first contact part. A material of at least a portion of the first contact part is different to a material of the second contact part.
In a fourth aspect, there is provided a contact piece for a vacuum interrupter. A material of the contact piece is Ag/C or WCAg/C or WCAg/C or Cu/C or CuCr/C or WCu/C or Cu or WCCu/C or CuCr or CuCr/C or WCu/C or WCCu/C or MoCu/C or WCMo/C or MoCCu/C.
The above aspects and examples will become apparent from and be elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments will be described in the following with reference to the following drawings:

Fig. 1 shows an example of a contact piece and its stem, with this also being termed a carrier;
Fig. 2 shows an example of a vacuum interrupter in the open position;
Fig. 3 shows examples of contact pieces and stems;
Fig. 4 shows examples of contact pieces and stems;
Fig. 5 shows examples of contact pieces and stems;
Fig. 6 shows an example of a vacuum interrupter in the open position; and
Fig. 7 shows examples of contact pieces and stems.

DETAILED DESCRIPTION OF EMBODIMENTS

Figs. 1-7 relate to a vacuum interrupter and contact pieces.
In an example, a vacuum interrupter comprises, a first carrier 101 and a second carrier 102. The first carrier comprises a stem 10 and a contact piece (1). The second carrier comprises a stem 10 and a contact piece 1. A carrier can be termed a contact piece with its stem. The contact piece of the first carrier comprises a first contact part 30 and a second contact part 20 surrounding the first contact part. The contact piece of the second carrier comprises a first contact part 30 and a second contact part 20 surrounding the first contact part. The contact pieces having a part 30 surrounded by part 20 is clearly shown in Figs. 1-7. Here it can be seen that the parts of the contacts facing each other have a central part 30 and a part 20 outside of the central part, surrounding it. The part 20 can be underneath part 30, or just around the outside, with the central part 30 going all the way through the contact piece to the stem 10. This is what is meant by "surrounding". A material of at least a portion of the first contact part of the first carrier is different to a material of the second contact part of the first carrier. Additionally or alternatively a material of at least a portion of first contact part of the second carrier is different to a material of the second contact part of the second carrier.
In an example, a material of the first contact part 30 of the second carrier is the same as a material of the second contact part 20 of the second carrier.
In an example, the material of the first contact part 30 of the second carrier is WCAg and the material of the second contact part 20 of the second carrier is WCAg.
In an example, the material of the first contact part 30 of the second carrier is WCAg/C and the material of the second contact part 20 of the second carrier is WCAg/C.
In an example, the material of the first contact part 30 of the second carrier is Cu/C and the material of the second contact part 20 of the second carrier is Cu/C.
In an example, the material of the first contact part 30 of the second carrier is CuCr/C and the material of the second contact part 20 of the second carrier is CuCr/C.
In an example, the material of the first contact part 30 of the second carrier is WCu/C and the material of the second contact part 20 of the second carrier is WCu/C.
According to an example, in a deactivated state the vacuum interrupter is configured hold the contact piece of the first carrier spaced from the contact piece of the second carrier and in an activated state the vacuum interrupter is configured to bring the contact piece of the first carrier and the contact piece of the second carrier into contact with one another.
According to an example, in a deactivated state the vacuum interrupter is configured hold the contact piece of the first carrier in contact with the contact piece of the second carrier and in an activated state the vacuum interrupter is configured to separate the contact piece of the first carrier from the contact piece of the second carrier. According to an example, the first carrier is a fixed contact carrier and the second carrier is a movable contact carrier, and in the activated state the vacuum interrupter is configured to move the second carrier.
According to an example, the first carrier is a movable contact carrier and the second carrier is a fixed contact carrier, and in the activated state the vacuum interrupter is configured to move the first carrier.
According to an example, the material of all of the first contact part of the first carrier is different to the material of the second contact part of the first carrier. Additionally or alternatively the material of all of the first contact part of the first carrier is different to the material of the second contact part of the first carrier.
According to an example, a junction between the first contact part 30 and the second contact part 20 of the contact of the first carrier defines a plane. This can be seen in Figs. 1-7. For example referring to Fig. 1 the first part 30 is an insert into the second part 20. The upper edge of the hole in part 20 is a circle, that forms a junction with part 30 (the upper edge of part 20 does not need to touch part 30, and it is the upper edge of part 20 that forms a hole or recess, within which part 30 is located, that forms a plane). Thus this junction (the upper edge of part 20) in the form of a circle forms the plane. In the example of Fig. 1 the upper edges of the hole/recess of part 20 is again a circle and forms a plane and the upper surface of part 30 is flat and is in the plane, whilst for example in Fig. 3 the upper edges of the hole/recess of part 20 is again a circle and forms a plane, but now the upper surface of part 30 is below the plane, whilst in Fig. 4 the upper part of part 30 is above the plane. Continuing with the example being described here, the first contact part comprises a portion 35, 50 with a surface below the plane and the at least a portion of the first contact part is the remaining portion of the first contact part other than the portion with the surface below the plane. Additionally or alternatively a junction between the first contact part and the second contact part of the contact of the second carrier defines a plane, and the first contact part comprises a portion 35 with a surface below the plane and the at least a portion of the first contact part is the remaining portion of the first contact part other than the portion with the surface below the plane. Additionally or alternatively a junction between the first contact part and the second contact part of the contact of the first carrier defines a plane, and the at least a portion of the first contact part comprises a portion 36 with a surface above the plane. Additionally or alternatively a junction between the first contact part and the second contact part of the contact of the second carrier defines a plane, and the at least a portion of the first contact part comprises a portion 36 with a surface above the plane.
According to an example, the material of the second contact part of the first carrier is WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or Cu/C or MoCu/C or Cu or WCu or WCCu or WCCu/C or MoCCu/C or Ag/C or Cu. Additionally or alternatively the material of the second contact part of the second carrier is WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or Cu/C or MoCu/C or Cu or WCu or WCCu or WCCu/C or MoCCu/C or Ag/C or Cu.
According to an example, the material of the at least a portion of the first contact part of the first carrier is Ag/C or Cu/C or CuCr or CuCr/C or WCu or WCu/C or MoCu/C or Sn/C or C. Additionally or alternatively the material of the at least a portion of the first contact part of the second carrier is Ag/C or Cu/C or CuCr or CuCr/C or WCu or WCu/C or MoCu/C or Sn/C or C.
According to an example, a junction between the first contact part and the second contact part of the contact of the first carrier defines a plane, and the at least a portion of the first contact part is a conical pin 31 that projects outwards from the plane. Additionally or alternatively a junction between the first contact part and the second contact part of the contact of the second carrier defines a plane, and the at least a portion of the first contact part is a conical pin 31 that projects outwards from the plane.
According to an example, the material of the at least a portion of the first contact part of the first carrier is carbon. Additionally or alternatively the material of the at least a portion of the first contact part of the first carrier is carbon.
According to an example, the second contact part of the first carrier comprises one or more slits 40. Additionally or alternatively the second contact part of the second carrier comprises one or more slits 40.
According to an example, the first contact part of the first carrier comprises one or more slits. Additionally or alternatively the first contact part of the second carrier comprises one or more slits.
According to an example, the one or more slits in the first contact part of the first carrier are a continuation of the one or more slits in the second contact part of the first carrier. Additionally or alternatively the one or more slits in the first contact part of the second carrier are a continuation of the one or more slits in the second contact part of the first carrier.
According to an example, the material of the at least a portion of the first contact part of the first carrier is the same as the material of the at least a portion of the first contact part of the second carrier. Additionally or alternatively the material of the second contact part of the first carrier is the same as the material of the second contact part of the second carrier.
According to an example, a shape of the at least a portion of the first contact part of the first carrier is the same as a shape of the at least a portion of the first contact part of the second carrier. Additionally or alternatively a shape of the second contact part of the first carrier is the same as a shape of the second contact part of the second carrier.
In an example, a vacuum interrupter comprises a first carrier 101, and a second carrier 102. The first carrier comprises a stem 10 and a contact piece 1. The second carrier comprises a stem 10 and a contact piece 1. The contact piece of the first carrier is made from a first material. The contact piece of the second carrier is made from a second material. The following applies:

From the above, it is clear that an exemplar new contact piece for a vacuum interrupter comprises a first contact part 30, and a second contact part 20. The second contact part surrounds the first contact part. A material of at least a portion of the first contact part is different to a material of the second contact part.
In an example, the material of all of the first contact part is different to the material of the second contact part.
In an example, a junction between the first contact part and the second contact part defines a plane. The first contact part comprises a portion 35, 50 with a surface below the plane. The at least a portion of the first contact part is the remaining portion of the first contact part other than the portion with the surface below the plane.
In an example, a junction between the first contact part and the second contact part defines a plane. The at least a portion of the first contact part comprises a portion 36 with a surface above the plane.
In an example, the material of the second contact part is WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or Cu/C or MoCu/C or Cu or WCu or WCCu or WCCu/C or MoCCu/C or Ag/C or Cu.
In an example, the material of the at least a portion of the first contact part of the first carrier is Ag/C or Cu/C or CuCr or CuCr/C or WCu or WCu/C or MoCu/C or Sn/C or C.
In an example, a junction between the first contact part and the second contact part defines a plane. The at least a portion of the first contact part is a conical pin 31 that projects outwards from the plane.
In an example, the material of the at least a portion of the first contact part of the first carrier is carbon.
In an example, the second contact part comprises one or more slits 40.
In an example, the first contact part comprises one or more slits.
In an example, the one or more slits in the first contact part are a continuation of the one or more slits in the second contact part.
From the above, it is clear that an exemplar new contact piece for a vacuum interrupter is defined as follows: a material of the contact piece is Ag/C or WCAg/C or WCAg/C or Cu/C or CuCr/C or WCu/C or Cu or WCCu/C or CuCr or CuCr/C or WCu/C or WCCu/C or MoCu/C or WCMo/C or MoCCu/C.
The vacuum interrupters with new contact pieces and the contact pieces themselves are now described in further detail with respect to specific embodiments, where reference is again made to Figs- 1-7.
The new development described here relates to centric inserts into the vacuum interrupter (VI) contact pieces. The inserts consist of a second contact material. Different contact materials can then be used for 1) carrying the current in the closed position and for 2) interrupting the current in the opened position of the contactor.
The new development also relates to the use of carbide or graphite (graphene / fullerene or diamond) as a contact material for Medium voltage (MV) vacuum interrupters for their low chopping current behaviour. Designs are shown to overcome the known limitations of normal contact materials regarding the general requirements for MV VI contacts.
Fig. 1 shows a contact piece 1 on its stem, which can also be termed a carrier 101, 102. The stem 10 is a state-of the art stem, usually made of copper. The main part 20 of the contact piece is for example made of WCAg, as it is state of the art for contactors. The insert 30 in the contact piece is made of a different material than the main part 20, for example CuCr or WCCu. An insert 30 of a contact piece 1 is also termed a first contact part 30. The main part 20 of a contact piece 1 is also termed a second contact part 20.
Fig. 2 shows a VI 100 in an open position, having fixed and movable stems with contact pieces 101, 102 with inserts. Further, the main components of the VI according to the state of the art are shown: Upper and lower lids 110, 130, ceramic insulator 120, and bellows 140.
When the VI is closed, the contact pieces will mainly touch with their inserts 30. When the VI opens while current is flowing, an arc 201 will establish between the inserts 30.
The materials of 20 and 30 are chosen in a way that the arc voltage of the material of the insert 30 is generally higher than the arc voltage of the material of the main part 20. The result will be that the arc 201 will commute to the region between the main parts 20 of the contact pieces like the arc 202, as shown on the right hand side drawing of Fig. 2. The arc will deteriorate the main part 20 so that its resistance will increase. In the case of WCAg, the Ag will locally evaporate at the footpoints of the arc so that the component with the low electrical resistance will be depleted in the contact piece; the WC will remain as a supporting structure. This increase of electrical resistance can be the reason not to pass the testing according to the standards in the case of state-of-the-art contact pieces made entirely from WCAg. With an insert 30 that is shunned by the arc due to the higher arc voltage, and that is in the region where the contacts touch, this effect of increased resistance can be avoided.
For a contactor application, a low chopping current is important. The chopping current is determined by the material that is in contact with the arc. So, in the case of WCAg being the material of the main part 20, the low chopping current can be maintained. Further, it is important that the material of the insert 30 fulfils the other requirements for a contact material according to the application of the VI. CuCr has a typically higher arc voltage than WCAg, but for a contactor application its tendency to moderate welding might be too strong for the relatively weak drives of contactors. A suitable material for the inserts 30 has been found to be WCCu or WCCuAg, as these materials have a higher arc voltage than WCAg, but they do not have the same tendency to weld as CuCr.
Fig. 3 shows two features for the contact piece 1. For the introduction of a transverse magnetic field, slits 40 are introduced in the contact piece with inserts to make the arc move around the radial ends of the contact pieces, so that local overheating of the surfaces of the contact pieces is limited. The slits may also be in the region of the insert 30, as shown in Fig. 3, or the slits may be only in the main part 20 (not shown). The other feature shown in Fig. 3 is a hole or a recess 50 in the centre, first contact part, of the contact piece to support the commutation of the arc away from the centre of the contact pieces towards the main part 20.
Fig. 4 shows an elevation 31 of the insert 30 compared to the main part 20 to make sure that the contacts touch always with the insert 30 and not with the main part 20. As the commutation of the arc mainly depends on the material and not strongly on the length of the arc, the commutation of the arc 201 to the arc 202 will not be affected by the elevation 31.
Fig. 5 shows a contact piece on its stem. The stem 10 is a state-of-the-art stem, usually made of copper. Several advantageous materials for the main part 20, also called second contact part 20, and the part 30, also called insert or first contact part 30, of the contact piece are discussed below.
The new development discussed here achieves low chopping currents due to the usage of carbon in a certain manner. Carbon can be present in the main part 20 and/or the insert 30 as carbide or graphite (graphene, fullerene or diamond).
The lowering 35 of the insert is an option to ensure that the normal load current is conducted by the material of the main part 20 of the outer area. So, the selection of the material of the insert or pin 30 is not constricted by its ohmic resistance in these cases.
Alternatively, the pin or insert 30 can have an extension 36 above the surface of 20, as shown in Fig. 7. In these cases, the material of the pin or insert 30 must fulfil the requirements of a low resistance in the closed condition and a low tendency to micro weld.
As shown in the rightmost picture of Fig. 5, slits 40 may be added to all contact pieces for increasing the ability to handle arcs of high currents.
Fig. 6 shows a VI 100 in the open position, having fixed and movable stems with contact pieces 101, 102 with pins. Further, the main components of a VI according to the state-of-the-art are shown: Upper and lower lids 110, 130, ceramic insulator 120, bellows 140.
When the VI is closed, the contact pieces will only touch with their main parts 20. When the VI opens while current is flowing, an arc 201 will establish between the main parts 20. The behaviour of the arc is now different depending on the magnitude of the current:
For low currents, the arc 201 will travel towards the centre of the contact piece, represented as arc 202 in Fig. 6, as the arc voltage of the material of the pin or insert 30 of the inner area is lower than the arc voltage of the material of the main part 20 of the outer area. So, when the current approaches the zero-crossing, the low chopping current of material of the pin or insert 30 will apply.
For high currents, like short-circuit currents, the arc will be driven away from the centre by the Lorentz force of its current and supported by the pinch effect. So, the high short circuit interruption capability of material of the main part 20 will be applied.
Figure 7 shows several geometrical arrangements of the main part 20 (also termed second contact part) and the insert 30 (also termed pin or first contact part):

310: Arrangement of two contact pieces with increased pins. Both contacts may be made from the same combination of materials or from different combinations of material.
320: Arrangement of one contact piece with increased pin and one contact piece without pin.
330: Arrangement of two contact pieces without pins. Both contacts may be made from the same material or from different materials.
340: Arrangement of two contact pieces with conical pins without lowering or increase. Both contacts may be made from the same combination of materials or from different combinations of material. In the shown example, the diameter of pin 30 is relatively small compared to the total mating face of the contact pieces. Alternatively, larger pins 30 can be used that cover most of the mating face of the contact piece to ease the transition of low-current-arcs from the main part 20 to the pin 30 of the contact piece. This applies also to arrangement 350.
350: Arrangement of a contact piece with conical pin and a contact piece without pin.

The following describe a number of exemplar applications and embodiments:

Vacuum interrupter for contactor application:

The main part 20 of the contact piece is e.g. made of WCAg, as it is state-of-the-art for contactors. The pin 30 is made of a different material than the main part 20. The material of the pin 30 can mainly be selected for its low chopping current. Suitable materials for the pin 30 are carbide or graphite (graphene / fullerene or diamond)

Vacuum interrupter for circuit breaker application:

The main part 20 of the contact piece is for example made of CuCr, as it is state-of-the-art for circuit breakers. The pin 30 is made of a different material than the main part 20. The material of the pin 30 can mainly be selected for its low chopping current. The application of carbon in a certain manner allows the reduction of the chopping current significantly. Suitable materials for the pin 30 are carbide or graphite (graphene, fullerene or diamond).
The following relates to specific embodiments of the arrangements shown in Fig. 7

Arrangement 310 - two contact pieces with increased pins; the two contact pieces may be identical or different:

First contact piece: Pin 30 is made from Ag/C, main part 20 is made from WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or Cu/C or MoCu/C or Cu.
Second contact piece: Pin 30 is made from Ag/C, main part 20 is made from WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or Cu/C or MoCu/C or Cu.

First contact piece: Pin 30 is made from Cu/C, main part 20 is made from WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or MoCu/ or Cu.
Second contact piece: Pin 30 is made from Cu/C, main part 20 is made from WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or MoCu/C or Cu.
First contact piece: Pin 30 is made from MoCu/C, main part 20 is made from WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or MoCu/C or Cu.
Second contact piece: Pin 30 is made from MoCu/C, main part 20 is made from WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or MoCu/C or Cu.
In the following combinations, the materials of pin 30 and main part 20 are identical in the second contact piece, so in these cases there will be no assembly of part 20 and part 30 but only a common part main 20 and pin 30 with the combined shape:

First contact piece: Pin 30 is made from Ag/C, main part 20 is made from WCAg or WCAg/C.
Second contact piece: Pin 30 and main part 20 are both made from WCAg or WCAg/C.

First contact piece: Pin 30 is made from Cu/C or CuCr or CuCr/C or WCu or WCu/C, main part 20 is made from WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or MoCu/C or Cu.
Second contact piece: Pin 30 and main part 20 are both made from Cu/C.

Arrangement 320 - first contact piece with increased pin and second contact piece flat without pin.

No combinations are described here where Ag in one contact piece and Cu in the second contact piece would touch each other in the closed position, as the combination Ag and Cu has a strong tendency to weld.
First contact piece: Pin 30 is made from Ag/C, main part 20 is made from WCAg or WCAg/C.
Second contact piece is made from WCAg or WCAg/C
First contact piece: Pin 30 is made from Ag/C, main part 20 is made from CuCr/C or WCu/C
Second contact piece made from WCAg or WCAg/C.
First contact piece: Pin 30 is made from Cu/C, main part 20 is made from WCAg or WCAg/C.
Second contact piece made from CuCr/C or WCu/C.
First contact piece: Pin 30 is made from Cu/C, main part 20 is made from CuCr/C or WCu/C.
Second contact piece made from CuCr/C or WCu/C.
In case of Sn/C it has to be considered that Sn/c will become liquid during the brazing process of the VI, so combinations with pins made of Sn/C are limited to arrangements where the pin is in the lower contact (during the brazing process) and where the pin does not show an increase 36, i.e. the pin has to show a lowering 35 or it may be flat within the main part 20:

First contact piece: Pin 30 is made from Sn/C, main part 20 is made from WCAg or WCAg/C or CuCr/C or WCu/C.
Second contact piece made from WCAg or WCAg/C or CuCr/C or WCu/C or Cu/C.

Arrangement 330 - both contact pieces flat without pin and made from the same or from different materials:

One contact piece made from Ag/C.
Second contact piece made from WCAg or WCAg/C.
One contact piece made from WCAg/C.
Second contact piece made from WCAg or WCAg/C.
One contact piece made from Cu/C.
Second contact piece made from CuCr or CuCr/C or WCu or WCu/C or Cu.
One contact piece made from WCu/C.
Second contact piece made from CuCr or Cu.
One contact piece made from WCCu/C.
Second contact piece made from CuCr or CuCr/C or WCu or WCu/C or WCCu/C or Cu.
One contact piece made from MoCu/C.
Second contact piece made from WCMo/C or CuCr or CuCr/C or WCu or WCu/C or Cu.
One contact piece made from MoCCu/C.
Second contact piece made from CuCr/C or Cu.

Arrangement 340 - both contact pieces from the same material with flat or lowered conical pins:

Pin 30 is made from C, main part 20 is made from Cu or WCu or WCCu or WCCu/C or CuCr or CuCr/C or MoCu/C or MoCCu/C.
Pin 30 is made from C, main part 20 is made from Ag/C or WCAg or WCAg/C.

Arrangement 340 - both contact pieces from different materials with flat or lowered conical pins:

First contact: pin 30 made of C, main part 20 made of Cu.
Second contact: pin 30 made of C, main part 20 made of WCu or WCCu or WCCu/C or CuCr or CuCr/C or MoCu/C or MoCCu/C.
First contact: pin 30 made of C, main part 20 made of WCu.
Second contact: pin 30 made of C, main part 20 made of WCCu or WCCu/C or CuCr or CuCr/C or MoCu/C or MoCCu/C.
First contact: pin 30 made of C, main part 20 made of WCCu.
Second contact: pin 30 made of C, main part 20 made of WCCu/C or CuCr or CuCr/C or MoCu/C or MoCCu/C.
First contact: pin 30 made of C, main part 20 made of WCCu/C.
Second contact: pin 30 made of C, main part 20 made of CuCr or CuCr/C or MoCu/C or MoCCu/C.
First contact: pin 30 made of C, main part 20 made of CuCr.
Second contact: pin 30 made of C, main part 20 made of CuCr/C or MoCu/C or MoCCu/C.

Arrangement 350 - first contact with flat or lowered conical pin, second contact flat without pin:

First contact: pin 30 made of C, main part 20 made of Cu.
Second contact made of Cu/C or WCu or WCCu or WCCu/C or CuCr or CuCr/C or MoCu/C or MoCCu/C.
First contact: pin 30 made of C, main part 20 made of Cu/C.
Second contact made of Cu/C or WCu or WCCu or WCCu/C or CuCr or CuCr/C or MoCu/C or MoCCu/C.
First contact: pin 30 made of C, main part 20 made of CuCr.
Second contact made from CuCr, WCu or MoCu/C or MoCCu/C.
First contact: pin 30 made of C, main part 20 made of WCAg.
Second contact made from WCAg or WCAg/C or MoCu/C or MoCCu/C.
First contact: pin 30 made of C, main part 20 made of WCAg/C.
Second contact made from WCAg or WCAg/C or MoCu/C or MoCCu/C.
First contact: pin 30 made of C, main part 20 made of Ag/C.
Second contact made from Ag/C or WCAg or WCAg/C or MoCu/C or MoCCu/C.

The referred materials are:

Ag/C Silver with a few percent (0.1%...10%) of graphite; especially with 2% and with 4% of graphite.
WCAg Tungsten carbide silver, well known for contactor applications of MV Vls, especially with 10%...60% Ag
WCAg/C Tungsten carbide silver with a few percent (0.1%...10%) of graphite, especially with 10%...60% Ag and with 1% of graphite.
C Carbone, graphite, graphene, fullerene or diamond Cu Copper
Cu/C Copper with a few percent (0.1%...10%) of graphite; especially with 2% and with 4% of graphite.
CuCr Copper chromium with 18% ...35% of chrome, especially with 25% and with 35% Cr
CuCr/C Copper chromium with a few percent (0.1%...10%) of graphite and 18%...35% chrome, especially with 25% and with 35% Cr WCu Tungsten copper with 5%...40% of Cu
WCu/C Tungsten copper with a few percent (0.1%...10%) of graphite and 5%...40% Cu
WCCu Tungsten carbide copper with 10%...50% of Cu
WCCu/C Tungsten carbide copper with a few percent (0.1%...10%) of graphite and with 10%...50% of Cu
MoCu/C Molybdenum copper with a few percent (0.1%...10%) of graphite and with 10%...50% of Cu
MoCCu/C Molybdenum carbide copper with a few percent (0.1%...10%) of graphite and with 10%...50% of Cu Sn/C Tin with a few percent (0.1%...10%) of graphite

All percentages are weight percent.
The following relates to advantages of the material combinations:

Arc of nominal current

For all arrangements with at least one increased pin (arrangements 310 and 320): The arc is established at the location of the pin 30, as the current is flowing there in the moment of contact separation. The relatively low level of the load current compared to the short circuit current is not overstressing the material of the pin 30 (Ag/C, Cu/C, Sn/C).
At current zero, the low chopping current of Ag/C or Cu/C or Sn/C applies. Also the combinations where the pin is made of CuCr/C or WCu/C will show the low chopping current due to the content of C.
The combinations with pins made of WCAg, CuCr or WCu will also have a low chopping current due to the content of C of the opposing contact.
For all arrangements with flat contacts without pins (330):

The low chopping current of Ag/C or WCAg/C or Cu/C or WCCu/C or MoCu/C or
MoCCu/C applies independently from the location of the arc.

For all arrangements with pin or pins made of C (340, 350):
As the arc voltage of the material C of the inner area of pin 30 is lower than the arc voltage of the materials of the outer area of the main part 20, the arc of a low current will travel towards the inner area of the pin 30 and the low chopping current of C will apply.

Arc of short circuit current:

For all arrangements with at least one increased pin (310, 320):
While the arc is starting at the location of the pin 30, it will in short time be driven away from the centre of the contact pieces by the Lorentz force and pinch effect, so it will burn in the area of the main parts 20 of the contact pieces where the materials WCAg or WCAg/C or CuCr or CuCr/C or WCu/C are resistant against arcing. The chopping current will be low anyhow due to the high temperatures of the main part 20 in case of short circuit currents. Furthermore, the pin 30 will not be deteriorated by the high short circuit current.
For all arrangements with flat contacts without pins:
The possible short circuit current in case of Ag or Ag/C or Cu or Cu/C or Sn/C can be lower than known from for example WCAg, but still being sufficient for certain applications where the other advantages are more important, for example for load current switching of small motors.
For all arrangements with pin or pins made of C (340, 350):
Independently from its starting point, the arc will in short time be driven away from the centre of the contact pieces by the Lorentz force and pinch effect, so it will burn in the area of the main parts 20 of the contact pieces where the materials WCAg or WCAg/C or CuCr or CuCr/C or WCu or WCu/C or WCCu or WCCu/C or MoCu/C or MoCCu/C are resistant against arcing. The chopping current will be low anyhow due to the high temperatures of 20 in case of short circuit currents. Furthermore, the pin 30 will not be deteriorated by the high short circuit current.
Even Cu, Cu/C und Ag/C provide a certain resistance against arcing, which can be sufficient depending on the application.

Ohmic resistance:

For all arrangements with at least one increased pin (310, 320):
Here the pin 30 is the part that carries the normal load current of the contacts. The typical effect from prior arcing on Ag/C, Cu/C, Sn/C, CuCr/C or WCu/C is that C is depleted in the surface of the pin 30, so that pure metal remains at the surface of the pin 30 and therefore the ohmic resistance is low.
Materials like WCAg, CuCr or WCu are suitable here.
For all arrangements with flat contacts without pins (330):
The typical effect from prior arcing on Ag/C or WCAg/C or Cu/C or WCCu/C or MoCu/C or MoCCu/C or Sn/C is that C depleted in the surface of the pin 30, so that pure metal remains at the surface of the 30 and therefore the ohmic resistance is low.
WCAg is state-of-the-art for contactors, so it can also be used here.
For all arrangements with pin or pins made of C (340, 350):
Here, the main parts 20 of the contact pieces carry the normal load current of the contacts as it is the state of the art. In case the material of 20 contains C, the C will also be depleted at the surface due to the arcing, so that the ohmic resistance remains low.

Welding:

For all arrangements with at least one increased pin (310, 320):
Ag/C is well known for negligible micro welding. This behaviour is also valid for Cu/C, CuCr/C, WCu/C, Mo/C, WCCu/C, MoCCu/C and Sn/C due to the content of C.
For all arrangements with flat contacts without pins (330):
As at least one of the two contacts is made of a material containing a few percent of C, the tendency to micro-welding is very low also in these cases.
For all arrangements with pin or pins made of C (340, 350):
Here, the main parts 20 are characteristic for the welding behaviour. Even Cu, Cu/C und Ag/C provide a certain resistance against arcing, which can be sufficient depending on the application.

Manufacturing:

For all arrangements with at least one increased pin (310, 320):
The usual manufacturing process of Vls can utilize the connection of the VI components by brazing. Ag/C is more difficult here, as the C in the surface has the tendency to reject the solder. This can be overcome by a preceding heat treatment of the surface of the Ag/C, so that the surface consists of pure silver, or by an extrusion process where the Ag/C is surrounded by a tube made of pure silver, or by centric embedding of the Ag/C powder into the powder of the main part of the contact piece, for example WCAg, prior to the sintering of the contact piece.
In case the material of the main part of the contact is for example CuCr, a deep-drawn foil of Ni can be inserted between the CuCr and the Ag/C to avoid that too large quantities of brazing solder evolve from the mixture of Cu and Ag at soldering temperatures above 780°C.
For all arrangements with pin or pins made of C (340, 350): The pure carbon, is practically not brazeable. For the connection with the main part of the contact material 20 it is therefore given a conical shape 31 so that it is form-fitted in the main part of the contact and the stem. Brazing solder can be used to fill the gap between the main part 20 and the conical shape 31 and between the conical shape 31 and the stem. Further, brazing solder is suitable to connect the main part 20 and the stem.
The following reference numerals apply:

1 Contact piece with its stem
10 Stem
20 Main part of contact piece - also termed second contact part
30 Pin in contact piece - also termed insert or pin or first contact part
31 Conical pin in contact piece - a form of the first contact part 30
35 Lowering of 30 compared to 20 - a form of the first contact part 30
36 Increase of 30 compared to 20 - a form of the first contact part 30
40 Slits in contact piece
50 Central hole in contact piece - a form of the first contact part 30
100 Vacuum Interrupter
101 Fixed contact piece with stem
102 Movable contact piece with stem
110 Upper lid 1
20 Ceramic insulator
130 Lower lid
140 Bellows
201 Arc
202 Arc
310 Arrangement of two contact pieces with increased pins
320 Arrangement of one contact piece with increased pin and one contact piece without pin
330 Arrangement of two contact pieces without pins
340 Arrangement of two contact pieces with conical pins without lowering or increase
350 Arrangement of a contact piece with conical pin and a contact piece without pin

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed invention, from a study of the drawings, the disclosure, and the dependent claims.

Claims

A vacuum interrupter, comprising:
- a first carrier (101); and

- a second carrier (102);
wherein the first carrier comprises a stem (10) and a contact piece (1);

wherein the second carrier comprises a stem (10) and a contact piece (1);

wherein the contact piece of the first carrier comprises a first contact part (30) and a second contact part (20) surrounding the first contact part;

wherein the contact piece of the second carrier comprises a first contact part (30) and a second contact part (20) surrounding the first contact part; and

wherein a material of at least a portion of the first contact part of the first carrier is different to a material of the second contact part of the first carrier; and/or wherein a material of at least a portion of first contact part of the second carrier is different to a material of the second contact part of the second carrier.
Vacuum interrupter according to claim 1, wherein in a deactivated state the vacuum interrupter is configured hold the contact piece of the first carrier spaced from the contact piece of the second carrier and in an activated state the vacuum interrupter is configured to bring the contact piece of the first carrier and the contact piece of the second carrier into contact with one another; or wherein in a deactivated state the vacuum interrupter is configured hold the contact piece of the first carrier in contact with the contact piece of the second carrier and in an activated state the vacuum interrupter is configured to separate the contact piece of the first carrier from the contact piece of the second carrier.
Vacuum interrupter according to any of claims 1-2, wherein the first carrier is a fixed contact carrier and the second carrier is a movable contact carrier, and wherein in the activated state the vacuum interrupter is configured to move the second carrier; or wherein the first carrier is a movable contact carrier and the second carrier is a fixed contact carrier, and wherein in the activated state the vacuum interrupter is configured to move the first carrier.
Vacuum interrupter according to any of claims 1-3, wherein the material of all of the first contact part of the first carrier is different to the material of the second contact part of the first carrier; and/or wherein the material of all of the first contact part of the first carrier is different to the material of the second contact part of the first carrier
Vacuum interrupter according to any of claims 1-4, wherein a junction between the first contact part and the second contact part of the contact of the first carrier defines a plane, and wherein the first contact part comprises a portion (35, 50) with a surface below the plane and wherein the at least a portion of the first contact part is the remaining portion of the first contact part other than the portion with the surface below the plane; and/or wherein a junction between the first contact part and the second contact part of the contact of the second carrier defines a plane, and wherein the first contact part comprises a portion (35) with a surface below the plane and wherein the at least a portion of the first contact part is the remaining portion of the first contact part other than the portion with the surface below the plane.
Vacuum interrupter according to any of claims 1-4, wherein a junction between the first contact part and the second contact part of the contact of the first carrier defines a plane, and wherein the at least a portion of the first contact part comprises a portion (36) with a surface above the plane; and/or wherein a junction between the first contact part and the second contact part of the contact of the second carrier defines a plane, and wherein the at least a portion of the first contact part comprises a portion (36) with a surface above the plane.
Vacuum interrupter according to any of claims 1-6, wherein the material of the second contact part of the first carrier is WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or Cu/C or MoCu/C or Cu or WCu or WCCu or WCCu/C or MoCCu/C or Ag/C or Cu; and/or wherein the material of the second contact part of the second carrier is WCAg or WCAg/C or CuCr or CuCr/C or WCu/C or Cu/C or MoCu/C or Cu or WCu or WCCu or WCCu/C or MoCCu/C or Ag/C or Cu.
Vacuum interrupter according to any of claims 1-7, wherein the material of the at least a portion of the first contact part of the first carrier is Ag/C or Cu/C or CuCr or CuCr/C or WCu or WCu/C or MoCu/C or Sn/C or C; and/or wherein the material of the at least a portion of the first contact part of the second carrier is Ag/C or Cu/C or CuCr or CuCr/C or WCu or WCu/C or MoCu/C or Sn/C or C.
Vacuum interrupter according to any of claims 1-4, wherein a junction between the first contact part and the second contact part of the contact of the first carrier defines a plane, and wherein the at least a portion of the first contact part is a conical pin (31) that projects outwards from the plane; and/or wherein a junction between the first contact part and the second contact part of the contact of the second carrier defines a plane, and wherein the at least a portion of the first contact part is a conical pin (31) that projects outwards from the plane.
Vacuum interrupter according to claim 9, wherein the material of the at least a portion of the first contact part of the first carrier is carbon; and/or wherein the material of the at least a portion of the first contact part of the first carrier is carbon.
Vacuum interrupter according to any of claims 1-10, wherein the second contact part of the first carrier comprises one or more slits (40); and/or wherein the second contact part of the second carrier comprises one or more slits (40).
Vacuum interrupter according to any of claims 1-11, wherein the first contact part of the first carrier comprises one or more slits; and/or wherein the first contact part of the second carrier comprises one or more slits.
Vacuum interrupter according to claim 12 when dependent upon claim 11, wherein the one or more slits in the first contact part of the first carrier are a continuation of the one or more slits in the second contact part of the first carrier; and/or wherein the one or more slits in the first contact part of the second carrier are a continuation of the one or more slits in the second contact part of the first carrier.
Vacuum interrupter according to any of claims 1-13, wherein the material of the at least a portion of the first contact part of the first carrier is the same as the material of the at least a portion of the first contact part of the second carrier; and/or wherein the material of the second contact part of the first carrier is the same as the material of the second contact part of the second carrier.
Vacuum interrupter according to any of claims 1-14, wherein a shape of the at least a portion of the first contact part of the first carrier is the same as a shape of the at least a portion of the first contact part of the second carrier; and/or wherein a shape of the second contact part of the first carrier is the same as a shape of the second contact part of the second carrier.
A vacuum interrupter, comprising:
- a first carrier (101); and

- a second carrier (102);
wherein the first carrier comprises a stem (10) and a contact piece (1);

wherein the second carrier comprises a stem (10) and a contact piece (1);

wherein the contact piece of the first carrier is made from a first material;

wherein the contact piece of the second carrier is made from a second material; and

wherein the first material is Ag/C and the second material is WCAg or WCAg/C; or

wherein the first material is WCAg/C and the second material is WCAg or WCAg/C; or

wherein the first material is Cu/C and the second material is CuCr or CuCr/C or WCu or WCu/C or Cu; or

wherein the first material is WCu/C and the second material is CuCr or Cu; or

wherein the first material is WCCu/C and the second material is CuCr or CuCr/C or WCu or WCu/C or WCCu/C or Cu; or

wherein the first material is MoCu/C and the second material is WCMo/C or CuCr or CuCr/C or WCu or WCu/C or Cu; or

wherein the first material is MoCCu/C and the second material is CuCr/C or Cu.
A contact piece for a vacuum interrupter, comprising:
- a first contact part (30); and

- a second contact part (20);
wherein the second contact part surrounds the first contact part; and

wherein a material of at least a portion of the first contact part is different to a material of the second contact part.
A contact piece for a vacuum interrupter:
wherein a material of the contact piece is Ag/C or WCAg/C or WCAg/C or Cu/C or CuCr/C or WCu/C or Cu or WCCu/C or CuCr or CuCr/C or WCu/C or WCCu/C or MoCu/C or WCMo/C or MoCCu/C.