Stator Vibration Comparison for DFIM under the Influence of Sinusoidal and Converter Excitation to Rotor Circuit

Doubly Fed induction Machine (DFIM) has a very versatile application with rating ranges from a few kW in wind power applications to hundreds of MW in hydropower applications. The rotor circuit of this machine is connected to the grid through a back-to-back voltage source converter. If the frequency and order of exciting EM force conflicts with natural frequency of the machine structure, high level of vibration may result into mechanical resonance. The stator vibration of electrical machine is generated by the electromagnetic forces acting on the surface of the stator tooths. In this paper, a comparative analysis of stator vibration has been presented for DFIM with its rotor winding excited through pure sinusoidal excitation (an ideal case) and voltage source converter. Parameters selected for comparison are vibration acceleration and the associated deformation. Since converters are also a source of harmonics, electromagnetic forces so generated have been analyzed here. Modal analysis has also been done in addition to finding out the machine’s natural frequencies.