Analysis of Electromagnetic Torque Pulses of Squirrel Cage Induction Generator During Connection with Power Grid

The connection of the induction machine with a power grid causes pulses of an electromagnetic torque with a high gradient. This effect is especially dangerous in systems with a transmission gear of a large ratio, like in hydropower schemes, because the torque pulses can generate very high stress on the gearbox and turbine bearings. In this paper an electromagnetic torque of the squirrel cage induction generator during the connection with a power grid is investigated. The mono-harmonic circuit model of the squirrel cage induction generator is prepared and verified on the laboratory test bench. This model is used to analyze the electromagnetic torque curve. Special attention is put into investigation of a torque pulse amplitude. The reduction method of the pulse amplitude by using the series RL branch is also presented.