Contact Material of Through Hole Electrical Slip Ring: Which One to Choose?

 

Introduction

The contact materials of the through hole electrical slip ring mainly refer to its precious metals and carbon brush materials. This part is generally installed at the rotation center of the equipment, the end of the shaft or other positions on the shaft. They are used to establish continuous electrical connections for different devices to conduct current and signals. And, they were divided into a variety of specifications and material options. Do you know which one is the best for your equipment?

 

1. Common Contact Materials

(1) Precious Metal Materials:

 

lGold: The color of gold is golden yellow, the density is 19.32 g/cm3, the melting point is  1064.43℃, and it is not easy to oxidize. In the through hole electrical slip ring, gold is used as a contact material, with extremely low contact resistance in use, to ensure stable current transmission. It is highly conductive and thermally conductive, being most suitable for high-end electronic equipment and precision instruments. But its cost is relatively high.

 

lSilver: Silver has a bright silver-white luster, a density of 10.59 g/cm3, a melting point of 961.78℃, and is easy to react with sulfides. Silver is also very conductive, second only to gold, and is often used in combination with graphite to form silver-graphite brushes. The graphite particles of this brush are dispersed in the silver matrix to form a continuous high-conductivity path. It carries power transmission for large industrial equipment and power systems.

lPlatinum: Platinum has a density of up to 21.45 g/cm3, a melting point of 1772℃. It's highly resistant to oxidation and corrosion. Platinum is relatively rarely used in through hole slip rings because its cost is very high. In special fields (such as aerospace, high-end medical equipment, etc.), platinum is used as contact material.

 

(2) Carbon Brush Materials:

 

lGraphite: The main component of graphite is carbon. It has low hardness, but also low cost. When in relative sliding contact, it can form a graphite-containing film layer to resist wear and increase lubricity. However, graphite has a relatively high resistance coefficient and a large contact voltage drop, so it is only suitable for motors with general speed.

 

lCopper Graphite: It is composed of copper and graphite, and has both the conductivity of copper and the lubricity of graphite. This material has a relatively low resistance and is suitable for motors with low voltage and high current. For example, in some large industrial equipment such as cranes and mining machinery.

  

lSilver Copper Graphite: This material aims to combine the advantages of silver, copper and graphite. Its cost is at a medium level and is more suitable for equipment such as CNC machine tools and automated production lines.

 

2. Considerations for Selecting Contact Materials

lConductivity: Gold is highly conductive but expensive, with a typical conductivity of about 455,000 S/m. Its high cost makes it unsuitable for all through-hole slip rings. Silver has a conductivity of about 63×10⁶ S/m, and copper has a conductivity of about 58×10⁶ S/m. These materials are preferred in applications involving high-speed data transmission or large amounts of current. They are often alloyed or composited with other metals. This makes them moderately priced and harder, making them widely used to transmit current and signals.

lWear Resistance: Through hole slip rings are subject to constant friction and wear during operation. Highly wear-resistant materials can extend the service life of the slip rings, such as carbon-graphite composites. Its wear coefficient is about 10⁻⁶ to 10⁻⁷ mm³/Nm, which can withstand the mechanical stress of sliding contact. Some metals and alloys, such as tungsten carbide and hard chrome plating, also have very high hardness. They can also resist wear in harsh environments, but are generally more expensive.

lCorrosion Resistance: In different operating environments, through-hole slip rings may be exposed to moisture, chemicals, and other corrosive elements. Among many materials, gold can withstand the most chemical corrosion and is not easy to oxidize. 316 stainless steel and nickel-based alloys are also suitable for many industrial environments. They are relatively resistant to rust and corrosion from moisture, weak acids and alkalis.

lCost: Cost is always a factor that needs to be considered. Compared with precious metals such as gold and silver, carbon graphite materials are relatively cheap. They can provide good conductivity and wear resistance at a lower cost. However, graphite materials are only suitable for equipment running at medium and low speeds. In some cases, we can combine multiple materials to achieve the required performance while reducing costs. For example, using a silver-plated copper core, as well as copper graphite.

 

Conclusion

In short, ByTune suggest that, when selecting through-hole slip ring contact materials, the specific requirements of the application must be considered. Conductivity, wear resistance, and cost, etc. all need to be carefully evaluated. In this way, you can find reliable performance and budget-friendly materials more quickly and accurately.