Identification of mechanical impedance of an electric machine drive for drivetrain design

This paper proposes a method for identifying mechanical impedance of an electric machine drive for drivetrain design and analysis. The mechanical impedance describes the dynamics of an electric machine as seen from its mechanical terminals. It depends not only on the electric machine but also on the control system, which should be taken into account when analyzing torsional vibrations. If the black-box input-output time-domain models of the electric machine and its control system are available, the mechanical impedance can be extracted from simulations. The proposed identification method is based on signal injection in time-domain simulations. At steady-state operating points, an excitation signal is injected into the rotor speed and the response is observed in the electromagnetic torque. The method is validated by comparing the identified mechanical impedances with the corresponding analytical solutions.