engleski

Influence of Microslip on Harmonic Motion of Turbine Generator

This paper is concerned with the influence of the microslip in turbine generator rotor slot wedges on dynamic instability at speeds close to the first critical rotational speed. A simple microslip model, i.e., discrete numerical microslip model, has been used. Assuming thet vibration shape of the turbine generator is the first mode shape, energy input to the vibrations due to internal damping caused by microslip is analysed during one vibration period. For rotational speeds above the first critical rotational speed, the energy input is positive, which increases vibrations. The influence of wedge parameters, such as length, the force in the spring between the wedges and the rotor windings and the coefficient of friction, on the energy input to vibrations has been studied. It has been shown that the energy input grows almost linearly with the wedge cross-section area increase. The wedge length increase causes the energy input to grow asymptotically toward a certain definite value. The increase of both the cofficient of friction and the force in the spring between the wedges and the rotor windings causes the energy input to decrease asymptotically toward zero. The energy input decreases to zero in cases of high rotational speeds. It has been stated that the correct choice of the wedge parameters may have significant influence on the dynamic stability of the turbine generator rotating close to first critical rotational speed.

turbine generator; dynamic stability; microslip

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