Abstract: In gas-cooled electric machines with a closed cooling loop which is distributed over two heat exchangers, arranged on the upper or under side of the machine, only part of the circulating cooling gas is cooled so that the electric machine must be taken out of operation because of the danger of local ovewrheating. In order to overcome this, baffles are arranged adjacent to the heat exchangers so as to block the cooling gas on half the side of the opposite axial cooling gas passage regions of the heat exchangers, thus subdividing the cooling gas stream into two halves with opposite flow directions. The partial transfer of the cooling gas stream halves to the entire width of the axial cooling gas passage areas of the heat exchangers provides turbulence and a distribution of the cooling gas for uniform cooling also in the event of a failure of one heat exchanger.

Abstract: The grinding discs of a refiner driven by an electric motor carry on the end faces facing each other material-grinding barriers or cutters which are arranged in groups in sectors and extend parallel to each other. To reduce the torsional excitation of the rotor shaft of the electric motor occurring during the operation of the refiner as far as possible, the sectors have irregular pitch or different sector angles along the circumference of the grinding discs.

Abstract: A flywheel arrangement for an electrical machine having a shaft includes a flywheel and a flange-like structure on the shaft for defining a seating surface to accommodate the flywheel. Passages are formed in the structure for directing oil under pressure to the seating surface.