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Future high-speed electrical motor technology will utilise wellstream hydrocarbon gas as cooling medium. Such integrated motor-compressors are currently under qualification for use on the sea floor in the North Sea. A vital part of the insulation system is the resin used to impregnate the motor windings and the resins ability to withstand chemical aging caused by the components inside the wellstream gas. The purpose of the resin in such a machine is to give mechanical support to the winding and to fill all gaps and voids inside the mainwall insulation, which consists of a mica paper tape. Various types of epoxy resins were exposed to an environment consisting of hydrocarbon gas, condensate and a mixture of water and monoethylene glycol (MEG). The specimens were built by casting the resin into a mould and curing it in an oven according to the procedure recommended by the resin manufacturers. According to the tests, the epoxy novolac and bisphenol A epoxy resin with BCl 3 accelerator were able to withstand their tensile strength and e-modulus during the exposure far better than the bisphenol F epoxy resin. The influence of an accelerator in an epoxy anhydride resin system was detected. Resins accelerated with zinc naphthenate provided the highest modulus before the tests, but were not able to retain it during the exposure. Resins accelerated with BCl 3 seemed to tolerate the environment better. The tensile strength of the resin was also dependent upon the amount of BCl 3 accelerator used.

Small CHP plants within the range of one megawatt electric power and a few megawatts thermal power might be well suited in supplying heat and electricity for small communities. Hermetically sealed turbo-generator improves the cost-effectiveness of such small-power CHP plants. In such a structure, the low pressure, low temperature steam from the turbine flows through the airgap of the generator. On the other hand, a hermetically sealed turbo-generator sets very high demands for the generator design. Steam in the air-gap is a substance, which traditional insulating materials cannot tolerate. Also, the thermal design of the machine requires special attention. This paper introduces a turbo-generator design with steamresistant insulation system and proper thermal design to operate in a hermetic small-power CHP plant.

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