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Tungsten-Copper for SF6 circuit breakers.

WCu Switching ContactsTungsten copper (WCu) materials are used for arcing contacts in SF6 circuit breakers for high and medium voltage applications. At the heart of the switching chamber, WCu arcing contacts are exposed to extreme mechanical and thermal stresses, with temperatures ≥ 20,000 K being reached during arcing. 

 

 

 

 

Tungsten-copper has unique material properties. A high level of temperature resistance is one of the most important advantages of tungsten, while the copper content increases the electrical and thermal conductivity.

 

  • excellent arc resistance
  • outstanding electrical conductivity
  • high strength
  • good machinability 
  • very good thermal conductivity
  • low thermal expansion 

Typical properties and values for our WCu materials:

 

Material

A15Ni A20Ni A20NiF FG20 A25NiF A30Ni
W [wt.%] 85 80 80 80 75 70
Cu [wt.%] 15 20 20 20 25 30
Additives [wt.%] ≤ 1.0 ≤ 1.0 ≤ 1.0 ≤ 1.0 ≤ 1.0 ≤ 1.0
Grain size [µm] up to 50 up to 50 20 - 25 4 - 8 20 - 25 up to 50
Density [g/cm3] 15.7 15.2 15.2 15.2 14.5 14
Hardness [HV30] 205 200 190 220 190 135
Compressive strength [N/mm2] 250 200 240 350 160 60
Electrical conductivity [m/Ωmm2] 17 18 18.5 18.5 21 23
Thermal expansion [10-6/K] 7.5 8.9 8.9 8.8 9.7 11
Burn-off behaviour **** *** *** **** ** **

**** outstanding, *** very good, ** good 

 

Low levels of arc erosion: With the right material mix.

 

Burn-off behaviour of tungsten-copper By choosing the right proportions of tungsten and copper, we are able to optimize the product's arc erosion properties. We obtain the lowest arc erosion rates at a tungsten content of 80 % by weight. Depending on the voltage and current intensity as well as on economic considerations, we can vary the tungsten content between 60 and 90 % by weight to meet your exact requirements.

The arc erosion behavior of tungsten-copper is also affected by the grain size of the tungsten, depending on whether it is used as the cathode (C) or anode (A) and in an SF6 or air atmosphere:

 

burn-off behaviour of WCu 

Source: Gessinger, Melton, 1977

Electrical conductivity of our tungsten-copper materials:

Electrical conductivity of tungsten-copper

 

Our Ni-activated sintering process means that PLANSEE WCu materials have a low susceptibility to cracking while at the same time offering excellent electric conductivity.

Greater endurance: With a well defined grain structure.

A15Ni

A15Ni

A20Ni

A20Ni

A20NiF

A20NiF

FG20

FG20

A25NiF

A25NiF

A30Ni

A30Ni

 

The higher the applied voltage and current, the more resistant to arc erosion the contact material must be. PLANSEE is able to modify the arc erosion resistance of WCu by, among other things,choosing the right grain size for the tungsten. 

Ready to install: WCu contact systems.

Ready to install Komponente

 

Ready-to-install contact systems help save you time. Just contact us! We can also cut your assembly times.

 

 

From the raw material to the finished product, we handle every production stage in-house: Our specialists at PLANSEE Powertech will develop your own customized materials with high arc erosion resistance and perform cost-effective, near-net shape sintering, back-casting, machining, joining, coating and assembly operations. This ensures that you benefit from reliable high quality.

WCu contact materials for use in vacuum.

WCu Ready-to-install component for vacuum chambers WCu contacts for ring ain units and reclosers

We also have the right materials for use in vacuum chambers, for instance in ring main units or reclosers. Switch contacts in VFG (very fine grained) quality are ultra-pure and boast outstanding electric conductivity. We offer different VFG materials with three different levels of copper content to meet different requirements:

 

 

  • VFG10 (90 % tungsten by weight, 10 % copper by weight)
  • VFG20 (80 % tungsten by weight, 20 % copper by weight)
  • VFG30 (70 % tungsten by weight, 30 % copper by weight)

 

Typical properties and values for our VFG materials:

 

Material

VFG10 VFG20 VFG30
W [wt.%] 90 80 70
Cu [wt.%] 10 20 30
Grain size [µm] 4-8 4-8 4-8
Electrical conductivity [m/Ωmm2] 22 25 30
Density [g/cm3] 16.5 15.2 14
Vickers hardness [HV] 220 210 130
O2 content [ppm] 50 50 50
N2 content [ppm] 20 20 20
H2 content [ppm] 5 5 5

 

We use powder metallurgical techniques to manufacture our composite materials so that we can offer you precisely the combination of different material properties that you need. The most important steps: We mix the input materials and then press and sinter the resulting material. This is the most cost-efficient way of giving our contact materials the required electrical properties.

 

Microstructure VFG10

 

Microstructure VFG20 

 

Microstructure VFG30 

VFG 10    VFG 20   VFG 30 

From idea to product in record time.

FEM image of a WCu switching component To achieve the perfect design for a switch contact, we combine the material data for our WCu materials with the thermal and mechanical conditions they will be subjected to.

 

 

 

 

In a remarkably short time, our engineers develop switch contacts with outstanding make/break capacity and a particularly long service life. It goes without saying that we use state-of-the-art FEM and CAD methods for this work. The FEM image, for instance, shows the stress simulation for a tulip contact.

Have you got a new idea? We'll help you put it into practice. Thanks to our know-how and efficient production for arcing contacts, we save time, boost performance and help reduce switching chamber maintenance costs.

 

Many power engineering groups have been calling on our experience for years.

Schneider Electric also appreciates the top performance we provide and awarded us as a "preferred supplier" for several times.

More products for power engineering.

Find out more about our copper-chromium and tungsten carbide-silver switching contacts.

Set us a challenge!

Mike Böning will identify the best material and design solution for your application.

 

Tel: +41 62 7691062
mike.boening@plansee.com

 

 

Set us a challenge!

 

Mike Böning will identify the best material and design solution for your application.

 

Tel: +41 62 769 10 62
mike.boening@plansee.com
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