Demands on insulation
In high-voltage systems, the operating voltage available from the drive battery is always above 200 V, often above 500 V. Some OEMs even use around 800 V. These high voltages place very high demands on the electrical insulation. The feedthrough terminals are a particular challenge for the automotive industry and its suppliers. For a long time, high voltage was not rooted in the DNA of this industry. “SCHOTT can, however, point to more than 80 years of experience in sealing metal to glass,” says R&D manager Akira Fujioka. “We have been producing such components for stationary air conditioners and refrigerators for over 60 years,” he adds.
The conditions in road vehicles are extreme. Meeting the industry’s usual requirements in terms of environmental factors, vibrations and severe temperature fluctuations is a tough challenge. In addition, there are the conditions in the compressor itself. The terminal must withstand the various refrigerants such as R134a, R1234yf and R744 (CO₂). At an operating pressure of up to 200 bar (20 megapascals), carbon dioxide makes the greatest demand. The insulation also has to withstand the high voltage. Creepage distances are particularly critical. SCHOTT uses several high-quality materials to optimize the design, including glass. This acts as an electrical insulator and separates the metal contact pins from the support plate. Glass is a core competence of SCHOTT. For 140 years, the company has been known for special high-quality glass types. The company also has a high level of expertise in connecting glass to metal.
Synthetic elastomer for extra protection
There is another material that makes electric compressor terminals from SCHOTT unique, namely an elastomer. While glass is responsible for the actual mechanical connection, the parts made of synthetic rubber prevent condensation which would otherwise shorten the creepage path and encourage sparkover. The elastomer can of course withstand the different lubricating oils for compressors such as PAG and POE. SCHOTT uses different sealing materials on the inside and outside. “After conducting an extensive series of tests our engineers have found the ideal combination,” says Akira Fujioka. The elastic components make the connections more reliable and durable. The highest quality standards also apply to the carrier plates. They must be very flat and smooth so that they too sit tight against the compressor housing.