Selischi - The Polytechnical Institute of Bucharest ROMANIA
Guzun - The Polytechnical Institute of Bucharest ROMANIA

Economic reasons are imposing for the large water power pumping stations to be driven by the medium speed synchronousimotors-, as in the case under study, rated 2 x 10 MN, 1000 rpm, 6 W. On the same way of considerations, the direct asynchronous-starting seems to be the most attractive among several other methods offered by the standard coarses in electrical machines. However, the simplicity of the direct start-up scheme is balanced by other serious inconvenients such as heavy stresses imposed on both sides, the motor and the supply ing network; well designed and selected with starting squirrel cage, could sustain prolonged stresses during the start-up period within non-prohibitive starting time, resulting from acceptable.dynamic torque. The latter applied to the motor is imposed to the driving scheme by the level of the short, circuit power existing in the supplying network, here levelled at 500 and 700 MVA for the step 110 kV. The problem is to point out the right scheme to ensure the safer start-up regime, heaving the data of the short circuit level and the water resistant. torque from the pump.