On wound rotor induction machine rotor electrical unbalance recognition using stator frame vibration spectral analysis

This paper investigates the torque and vibration signal spectra of wound rotor induction machines when subjected to different levels of rotor electrical unbalance. A harmonic machine model numerical study is first performed to identify the electromagnetic torque signal spectral components related to operation without or with electrical unbalance. Once the understanding of the correlation between the operating conditions and the torque spectral content is established, a series of laboratory tests are conducted to evaluate the manifestation and detectability of electromagnetically induced vibration matching the identified disturbance frequencies in the torque model study. The magnitude of rotor electrical unbalance spectral signature in the vibration signal is assessed for a range of unbalance levels in measurements taken on two different wound rotor machine designs.