Frequency-Cascade Electric Drive System for Induction Motor Starting Torque Stabilization

It is necessary to stabilize the dynamic torque of the motor at the start of mechanisms with cyclical action, such as machine tools, which perform the machining of large cylindrical parts and require their rotation. The research carried out has shown that such requirements are met by the proposed system of frequency cascade electric drive, based on an induction motor with a phase-wound rotor and equipped with additional elements enabling the transfer of sliding energy from the motor-rotor circuit to the DC link of the frequency converter. A pulsed control system of the inverter input current and correction of the control signals as a function of the motor torque value determined by means of a torque observer is proposed.