By Shannon Wetzel, MetalcastingDesign.com 

As electricity navigates the jungle of society, copper clears its path. Second only to silver in conductivity, copper makes our reliance on electricity possible. In 2006, an estimated 21,000 tons of copper-base castings were shipped to the electrical industry. Whether it’s a circuit breaker component or a computer part, copper plays an important role in the efficiency of electrical equipment.

This 6,000-amp rectifier for a high-amperage industrial electrical breaker cast via permanent mold was converted from an assembly of machined copper bar stock. Prototypes failed to pass the required 6,000-amp heat rise tests. The one-piece, 34-lb. pure copper casting design, which incorporated heat-dissipitating fins and eliminated resistive mechanical joints, passed the heat rise test.

Amped Up

Recently, the electrical industry has trended toward energy conservation. In order to dissipate as much electricity as possible, components made of materials with the highest levels of conductivity are increasingly in demand.

Although silver has the highest conductivity of any metal, it’s expensive and easily tarnished. Pure copper exhibits slightly less conductivity, but its relative affordability has made it the default material for these applications. Producing a high quality part that meets pure copper standards is difficult, but metalcasters have shown it’s possible—and common—to meet the requirements.

Metalcasting facilities with tight operations and good melting control can help electrical part designers benefit from pure copper’s conductivity and the casting processes’ geometrical flexibility.

“Any part can be made in various processes, but only one is optimal,” said Karl Schweisthal, president of permanent mold caster Piad Precision Castings, Greensburg, Pa. “We’ve converted copper parts that are brazed together into one-piece castings, as well converted parts machined from bar stock.”

A major electrical equipment manufacturer needed a new breaker design that was compact and cost efficient in order to compete with international firms. A copper line conductor used in a 1,200-amp breaker originally was machined from an extruded bus bar to which a smaller copper pad was brazed. The manufacturer worked with Piad to design a one-piece precision casting that eliminated all secondary operations except for the tapping of two holes. Additionally, the electrical performance of the line conductor was improved. The line conductor passed all heat rise and short circuit tests and exhibited a smooth surface finish adequate for electrical contact surfaces.