Copper alloy electrical contact

for circuit breakers

Overview
Copper‑chromium (CuCr) switching contacts are used in vacuum circuit breakers covering 1 kV to 245 kV to interrupt and close circuits. Copper provides high electrical and thermal conductivity while chromium increases resistance to arc erosion and reduces welding tendency by acting as a heat‑resistant phase and oxygen getter.

Your advantages at a glance

• Good mechanical strength and low gas content
• Excellent resistance to arc erosion
• Low welding tendency
• Economical near‑net shape production by powder metallurgy
• Effective dissipation of short‑circuit currents
• Breaking capacity up to 90 kA (depending on design)

Copper‑chromium compositions and recommendations
Multiple CuCr compositions are available depending on the application. For effective arc extinction at low and high frequencies with low chopping current, chromium ≈ 25 wt% (e.g. CC75) is recommended. For superior erosion resistance and minimal wear, chromium contents in the 25–43 wt% range (e.g. CC75–CC57) provide best results. Typical designations: CC98, CC90, CC75, CC70, CC57.

Comparison table (selected typical values)
Material | CC‑98 | CC‑90 | 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 | +++ | +++ | ++++
Chromium (wt%) | 2 | 10 | 25 | 30 | 43
Copper (wt%) | 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 | +++ | +++ | ++++

Manufacturing and quality
CuCr switching contacts are produced by powder metallurgy: high‑purity copper and chromium powders are pressed and sintered to near‑net shapes and then machined to final geometry. Powder metallurgy yields a fine‑grained, homogeneous microstructure with improved durability compared to melt routes. Products are manufactured under ISO 9001 quality management and can be tailored to customer specifications.

Applications / Typical use
Used in arcing chambers and on contact surfaces of vacuum circuit breakers where resistance to arc erosion, low welding tendency and good short‑circuit dissipation are required. Recommended grades: CC98, CC90, CC75, CC70, CC57.

Characteristics / technical specifications

• Typical grades: CC98, CC90, CC75, CC70, CC57
• Chromium content: 2–43 wt% (grade dependent)
• Copper content: complementary to chromium (e.g. CC98 = 98 wt% Cu)
• Electrical conductivity: ~48–21 m/Ω·mm² (grade dependent)
• Density range: ~7.60–8.70 g/cm³
• Hardness (HV30): ~70–138 (depending on grade)
• Typical impurity levels (O/H/N): O 150–700 ppm, H 5–10 ppm, N 15–110 ppm
• Breaking capacity: up to 90 kA (application dependent)
• Manufacturing: powder metallurgy (press & sinter), near‑net shape, final machining
• Standards: produced according to ISO 9001