In vacuum interrupters, contact materials are critical to ensure reliable operation and service life. The main materials of vacuum interrupter contacts usually include:

1. Copper (Cu): It is often used because of its excellent electrical conductivity. Copper can form alloys with other materials to enhance their properties.

2. Copper alloy: Commonly used alloys include copper-chromium alloy (Cu-Cr) or copper-tungsten alloy (Cu-W). These alloys have higher wear resistance and thermal stability, which is essential for discontinuous high current.

3. Silver (Ag): Sometimes used for its excellent conductivity and low contact resistance. Silver contacts are often used in applications with higher performance requirements, but may be less common due to cost and easy oxidation.

4. Tungsten (W): Tungsten is known for its high melting point and is often used in high-voltage applications. It can be used as a contact tip or as part of a composite material.

5. Composite Materials: Some vacuum circuit breakers use composite materials that combine different metals to optimize performance characteristics such as conductivity, wear resistance, and thermal stability.

The choice of contact material depends on the specific application, operating conditions and performance requirements of the vacuum interrupter. The material must be able to withstand high temperatures, mechanical wear and the effects of arcing during operation.

 

 

 

High voltage vacuum circuit breakers often use copper-chromium (Cu-Cr) contacts for several important reasons:

 

1. High Electrical Conductivity: Copper is known for its excellent electrical conductivity, which is critical to minimizing power losses and ensuring efficient operation in high-voltage applications.

2. Arc resistance: Adding chromium to copper enhances the material's ability to resist arcing. Arcing occurs when contacts are disconnected, and copper-chromium alloy helps to extinguish the arc quickly, thereby reducing contact wear and extending its service life.

3. Wear resistance: Copper-chromium contacts have higher wear resistance than pure copper contacts. This is especially important in applications where contacts are frequently switched on and off, as it helps maintain the integrity of the contact surface over a long period of time.

4. Thermal stability: The alloy has good thermal stability, which enables it to perform well at high temperatures generated during operation, especially under fault conditions.

5. Mechanical Strength: Copper-chromium alloy has enhanced mechanical strength, which is beneficial to maintain contact integrity and reliability under mechanical stress.

6. Reduced contact resistance: The combination of copper and chromium helps maintain low contact resistance, which is critical for efficient operation and minimizing heat generation during current flow.

 

Overall, the use of copper-chromium contacts in high-voltage vacuum circuit breakers provides a balance between electrical performance, durability, and reliability, making them well suited for demanding applications.