Speed control device for ac electric motor

摘要

A speed control apparatus of an AC motor according to the invention has current controllers for performing proportional integration control of an excitation component current and a torque component current of two components on rotating Cartesian two-axis coordinates into which a current of the AC motor is separated. The speed control apparatus comprises a first subtracter 1 for finding torque component voltage saturation amount DeltaVq from torque component voltage component Vq' output from a torque component current controller 47a and torque component voltage command Vq* output from a torque component voltage limiter 54a, a first integrator 2 for holding the torque component voltage saturation amount DeltaVq, a magnetic flux command corrector 3a for outputting magnetic flux command correction amount Deltaphi2d from the held torque component voltage saturation amount DeltaVq' and rotation angular speed omega of Cartesian two-axis coordinates, and a second subtracter 4 for subtracting the magnetic flux command correction amount Deltaphi2d from magnetic flux command phi2d* and outputting magnetic flux correction command phi2d*cmd.