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CuCr switching contacts

Copper-chromium switching contacts for medium voltage

Vacuum circuit breakers in a voltage range of 1 KV to 245 KV are used in millions of applications with our copper-chromium contacts to interrupt and close circuits for industrial companies and households alike.

Copper provides excellent electrical and thermal conductivity for the contact material – the most important prerequisite for ensuring minimum loss of the flowing electricity. When the switching contacts break the circuit, an arc is formed that places high stress on the material. Thanks to the use of our heat-resistant chromium, the resistance to arc erosion of the CuCr contact is increased enormously, thus reducing the welding tendency significantly. Therefore, chromium prevents the CuCr contacts from welding together. Chromium also has a high oxygen affinity and acts as a getter when gases are released during switching processes.

Your advantages at a glance:

  • Mechanical strength and low gas content

  • Excellent resistance to arc erosion

  • Low welding
    tendency

  • Economical production of near-net shapes

  • Very good dissipation of short-circuit currents

  • Breaking capacity up to 90 kA

Copper and chromium compositions for your applications

We have developed several material compositions with copper-chromium for your applications. A chromium content of 25 percent by weight is your best bet if arc extinguishing at both low and high frequencies as well as at a low chopping current is crucial for your application. However, if erosion resistance and a low tendency to wear are critical then a chromium content of 25 to 43 percent by weight will provide the best results.

You can see here where our copper-chromium materials are used in the arcing chamber. The materials must be particularly resistant to arc erosion especially at the contact surfaces. For this, we recommend our proven materials with a chromium content of 2 to 43 percent by weight: CC98, CC90, CC75, CC70, and CC57.

Comparison of our copper-chromium materials for switching contacts and electrode supporting materials:

 

Material CC-98 CC90 CC-75 CC-70 CC-57
Power interruption ο ο ++++ ++++ ++++
Burn-off behavior ο ο +++ ++++ ++++
Conductivity ο ο ++++ +++ ++
Chopping current ο ο ++ +++ ++++
Wear properties ο ο ++ +++ ++++
Capacitive interruption ο ο +++ +++ ++++
Amount of chromium (percent by weight) 2 10 25 30 43
Amount of copper (percent by weight) 98 90 75 70 57
O content [ppm] 150 215 650 675 700
H content [ppm] 5 5 5 5 10
N content [ppm] 15 30 100 105 110
Density [g/cm3] 8.70 8.6 8.05 7.90 7.60
Hardness [HV30] 110
(HB62.5/2.5)
138
(HB62.5/2.5)
70 75 85
Electrical conductivity [m/Ωmm2] 48 42 31 28 21
Welding resistance ο ο +++ +++ ++++

++++ excellent, +++ very good, ++ good ο CC-98 is used as support material (electrode) contact.
The table shows typical values for indication purpose only. For construction and design, please order our more detailed specifications.

Advantages of powder metallurgy manufacturing

We only use high-quality chromium- and copper powder in the powder metallurgy manufacturing process for our CuCr contact materials. We press and sinter the switching contacts to the final shape and near-net shape, and then process them into the final switching contacts. This results in a very fine-grained and homogeneous microstructure, which makes our switching contacts particularly durable.

Numerous practical tests prove that our switching contacts have a significantly longer service life than products produced by melting processes. When contact materials are made using melting processes, the individual output materials are less evenly distributed. An accumulation of copper can lead to contact welding and cause considerable damage to the vacuum switch.

Highest purity and quality

The purity of the contact material has an important influence on its switching properties. The lower the oxygen content in the switching contact, the lower the probability of re-ignition. That's why we use particularly pure materials.

We manufacture all CuCr switching contacts according to ISO 9001 guidelines. The design of our switching contacts is geared towards the requirements of our customers. Our experts would be happy to help you select the optimal design and the most suitable material. Our Swiss location Plansee Powertech specializes in materials for switching contacts.

More about Plansee Powertech

Other products for energy technology

Are you interested in our other contact materials? Then please visit our product pages for switching contacts made of tungsten-copper as well as for use in a vacuum: