November/December 2020

TECHNOLOGY n 19 www.drivesncontrols.com November/December 2020 US RESEARCHERS HAVE developed a process that, they say, can boost the conductivity of copper wire by about 5%, thus either improving the efficiencies of electric equipment such as motors – or reducing their weight while operating with the same efficiency. The researchers, from Pacific Northwest National Laboratory (PNNL), have teamed up with General Motors to test the improved copper wire in components for vehicle motors. As part of a cost- shared research project, they validated the increase in conductivity and also found that the copper is also more ductile – it can stretch further before it breaks. In other respects, the material behaves like standard copper, so it can be welded and subjected to mechanical stresses with no loss of performance. No specialised manufacturing methods are needed to use the enhanced copper in motors. The new material can be used in any application that uses copper to transport electrical energy, including cables, power transmission systems, generators, batteries and wireless chargers. The improved performance is achieved by adding graphene – a highly conductive, extremely thin sheet of carbon atoms – to copper and using this to produce wire with a higher conductivity than pure copper. A first-of-its-kind machine, incorporating patented and patent-pending technologies, combines and extrudes the metal and composite materials. The process, called Shape (Shear-Assisted Processing and Extrusion), applies an oppositional, or shear, force by rotating a metal or composite as it is pushed through a die to create a new shape. Deforming the metal causes internal heating which softens it and allows it to be formed into wires, tubes or bars. “Shape is the first process that has achieved improved conductivity in copper at the bulk scale, meaning it can produce materials in a size and format that industry currently uses, like wires and bars,” says Glenn Grant, principal investigator at PNNL. “The benefit of adding graphene to copper has been investigated before, but these efforts have focused primarily on thin films or layered structures that are extremely costly and time-consuming to make. The Shape process is the first demonstration of a considerable conductivity improvement in a copper-graphene composite made by a truly scalable process.” Previous attempts to add graphene to copper have run into problems because the additives did not blend uniformly, creating clumps and pores within the structure. The new process eliminates the pores while also distributing the additives uniformly within the metal, which may explain the improved electrical conductivity. “Shape’s uniform dispersion of the graphene is the reason why only really tiny amounts of additive are needed – about six parts per million of graphene flakes – to get a substantial improvement of 5% in conductivity,” explains PNNL material scientist, Keerti Kappagantula. “Other methods require large quantities of graphene, which is very expensive to make, and still have not approached the high conductivity that we've demonstrated at a bulk scale. R&d engineers at GM have verified that the high-conductivity copper wire can be welded, brazed, and formed in the same way as conventional copper wire, suggesting seamless integration into existing motor manufacturing techniques. “Higher conductivity copper could be a disruptive approach to light-weighting and/or increasing efficiencies for any electric motor or wireless vehicle charging system,” says Darrell Herling of PNNL's Energy Processes and Materials Division. According to a report on electric vehicles produced by the US Department of Energy in 2018, motor efficiencies need to be improved to boost EV power densities. Additionally, components need to fit within increasingly smaller spaces available in vehicles. Reducing motor volumes has, until now, been limited by material properties and by the electrical conductivity limitations of conventional copper windings. ‘More conductive’ copper will lead to more efficient motors SIEMENS HAS announced a compact integrated drive system aimed at horizontal conveyor applications. The Sinamics G115D system combines a motor, frequency converter and gearbox, and is available in either wall-mounting (0.37–7.5kW) or motor-mounting (0.37–4kW) versions. The robust system is available in IP ratings up to IP66 and can be used in harsh environments, and in temperatures from –30 to +55°C. It is suitable for applications in intralogistics and airports, as well as in the automotive, and food and beverage industries. The drive system can be commissioned quickly and integrates with Siemens’TIA (Totally Integrated Automation) portal, including its Startdrive commissioning software, or the Sinamics G120 Smart Access Module (SAM) Web server tool for setup and diagnostics. The system also integrates with Siemens’ MindConnect portfolio and is compatible with Mindsphere applications such as Analyze MyDrives, enabling cloud-based analyses. Support for Profisafe and STO (Safe Torque Off ) SIL2 is built in, facilitating certification. The drive can be used with controllers such as the Simatic S7-1200 or Simatic ET200 for motion control. https://drivesncontrols.news/p6vt8 PNNL materials scientist Keerti Kappagantula holds an ultra-high conductivity copper wire with graphene additives produced using the PNNL-developed process that could help to boost motor efficiencies. Photo: Andrea Starr / PNNL n All-in-one distributed drive system targets conveyors