Power frequency control of a pump turbine as an example for the operation with adjustable speed of hydraulic machines

摘要

The characteristics of different types of hydraulic turbo machines are examined for the operation with adjustable speed. The investigation is made for a pump turbine with a Francis type runner, an axial type turbine with fixed as well as adjustable runner, and ifnally a Pelton turbine. Varspeed systems can be realised with different combinations of electrical machines and frequency converters. Howeve,r hte operating range of the frequency converter plays an important role for the optimization of the turbine characteristics and is therefore taken into account. For reaction turbines a more smooth running as well as reduced cavitation can be achieved with the variation of speed. Above all, the hydraulic efficiency especially at part load and for low head is considerably improved. This improvement can be achieved for Pelton turbiens as well. As an example, a power frequency control for a pump turbine is presented using adjustable speed. Copyright direct C 1998 IFAC