抄録
A stress measurement technique was developed in order to reduce the disturbance caused by electromagnetic field. Using this technique, a series of short circuit tests were carried out on 21000kVA two-pole turbine generators. The stress and displacement induced on the stator end windings were examined under various short circuit voltages. The mechanical strength of the stator end windings was discussed in comparison with the measured stress and the bending strength of stator windings and was also discussed in relation to the variations in tangent delta and breakdown voltage characteristics. The results obtained are as follows.
(1) The stress measurement technique developed in this study is effective for the stress measurement on electric appliances which are exposed to strong magnetic field.
(2) The stator end windings can be bent repeatedly tangentially in the direction to increase the stator end windings' curvature and radially in the opposite direction to the rotor.
(3) The maximum amplitudes of stress and displacement of the stator end windings increase in proportion to the square of short circuit voltage. But they depend on the magnitude of the direct component in short circuit current and tend to increase with it.
(4) When the direct current component appears relatively large, the predominant frequency of the stress and displacement is 60Hz, but with decreasing of direct current component 120Hz frequency becomes predominant. When it is small, 120Hz frequency is predominant.
(5) It is considered that within this test condition there is no mechanical damage which would cause the reduction of electric characteristics under further service operation.
