Contemporary electric motors used in electric vehicles and traction drives operate under conditions that only a decade ago were considered extreme. Rising power density, higher operating frequencies, increasingly tight windings, and the demand for long service life under fluctuating climatic conditions mean that conventional impregnating resins are more and more often proving insufficient. Manufacturers are looking for solutions that simultaneously deliver excellent electrical insulation, high-temperature resistance, and stability against moisture and cyclic thermal loads. It is precisely in this context that the position of SILRES® H62 C resin is becoming increasingly prominent on the European market.
SILRES® H62 C is a one-component, solvent-free silicone resin based on phenyl-methyl resins, developed by WACKER. The product is ready to use and intended primarily for the impregnation of coils by the vacuum pressure impregnation (VPI) method. Unlike many traditional epoxy or polyester systems, SILRES® H62 C contains no solvents, which translates into zero VOC emissions, virtually zero shrinkage during curing, and the ability to safely cure in thick layers even when in contact with air. After curing, it forms a hard, transparent coating with a Shore D hardness of approximately 65 that retains excellent insulating properties over a very long period.
Particular attention is drawn to the thermal resistance of this resin. With an RTI of 239 °C, SILRES® H62 C meets the requirements of insulation classes N and R according to DIN EN 60085. In practical terms, this means that motors and generators can be designed to operate at higher winding temperatures without the risk of rapid insulation degradation. By comparison, many conventional organic resins begin to lose their properties already in the 180–200 °C range, especially under prolonged exposure and in the presence of moisture. The phenyl silicone structure of SILRES® H62 C withstands both continuous high temperatures and the rapid thermal cycles typical of traction motors and EV drives during dynamic driving far more effectively.
Another important advantage is the behaviour of the resin in the VPI process. Thanks to the possibility of reducing viscosity by heating to 60–80 °C (where viscosity drops to approximately 80 mPa·s), SILRES® H62 C penetrates even densely wound coils of modern high fill-factor motors very effectively. The absence of by-products during curing and the minimal shrinkage reduce the risk of voids and microcracks, which in the longer term become sources of partial discharges. In practice, this results in higher reliability and longer intervals between overhauls, which has a direct impact on the total cost of ownership (TCO) in both automotive and railway applications.
The environmental and regulatory aspect is also worth noting. European requirements concerning volatile organic compound emissions and REACH regulations are increasingly restricting the use of solvent-containing resins. As a completely solvent-free product, SILRES® H62 C makes it easier to meet these requirements and simplifies certification processes. In addition, the product complies with UL 94 V-0, which can be important when designing equipment that must meet fire safety standards.
The impregnation process using SILRES® H62 C is well-defined and repeatable. The winding is first thoroughly dried at elevated temperature, then subjected to vacuum, after which the vessel is filled with the heated resin. Following the wet vacuum phase, pressure is applied, and the winding is subsequently cured in an oven, preferably under continuous rotation, in order to achieve a uniform resin distribution and minimise drip losses. The manufacturer recommends that the thickness of the cured layer should not significantly exceed 100 μm – this minimises the risk of cracking caused by differences in the thermal expansion of the construction materials.
Beyond classic coil impregnation, SILRES® H62 C is also used as a binder for fibre composites and as a hydrophobising agent. In combination with suitable silicone elastomers, it is employed for sealing the ends of tubular heating elements, where it provides a durable moisture barrier even under high-temperature conditions.
For European manufacturers of electric motors, generators and traction drives, the choice of impregnating resin is no longer purely a technical decision – it is becoming an element of reliability and competitiveness strategy. SILRES® H62 C offers a combination of high thermal resistance, dielectric stability, weathering resistance and compliance with growing environmental requirements. As a result, it can genuinely extend the service life of windings and reduce the risk of costly field failures.
If you are interested in purchasing SILRES® H62 C or would like to discuss the possibility of using this resin in your impregnation processes, please write to us at: info@silray.pl
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