Assembly In Action: Heat-Conducting Polyurethane Extends Life of Transformers
May 31, 2011
At its manufacturing plant in Ajka, Hungary, Schwa-Medico GmbH Transformatorenbau & Industrieprodukte makes four types of electronic transformers specially designed for photovoltaic converters. The transformers, in turn, are sent to a plant in Germany, where they are installed in inverters and integrated into photovoltaic systems.
Hoping to increase productivity to meet market demand, Schwa-Medico recently installed an A300 material preparation and feeding system in its Hungary facility. Made by Scheugenpflug, the system pots Schwa-Medico’s coiled products with heat-conducting polyurethane, which dissipates any heat build-up in the transformer.
“We were looking for a technically advanced system that met all of our needs, was easy to operate and available at short notice,” says Wolfgang Schmidt, CEO of Schwa-Medico.
One of the challenges faced by the company is that its four transformers vary in shape and require different amounts of urethane for potting. The A300 met that challenge-thanks to its Windows-based interface, which can be programmed to a customer’s exact production requirements. In addition, the A300 can handle abrasive materials, such as the hard, jagged fillers in heat-conducting polyurethane.
Potting is carried out in two phases, which is standard for coiled products. Due to the polyurethane’s moisture sensitivity, all dispensed material is tempered, carefully homogenized and held under a constant vacuum.
In the first cycle, components are precisely metered by an eight-nozzle metering head fitted with a static mixer for two-component materials. Then the hardening agent is mixed thoroughly with the resin in the mixing tube and poured directly into the components in the vacuum chamber. The resin protects the transformers from any adverse environmental effects.
After the first potting cycle, which is conducted at a pressure of approximately 20 millibars, the vacuum chamber is ventilated so the resulting pressure difference fully immerses the coil in the filling material. The finishing layer is performed under normal atmospheric pressure. The system pots 112 parts per tray at an average cycle time of nine seconds per part.
Schwa-Medico machine operators who have worked with the A300 are satisfied with its ease of operation, simple programming options, reliable results and long-term stability. In fact, Schmidt says the system has enabled Schwa-Medico to provide a 20-year warranty on its transformers.
For more information on material preparation and feeding systems, call 770-218-0835 or visit www.scheugenpflug.de.