DC pre-excitation starting control for induction motor base on flux identification and compensation

Vector control can not be well applied directly to the starting of large-power induction motors. The starting current is so large as to cause damage to power-conductors and the whole control system. A novel pre-excitation control strategy is proposed in this paper. A magnetic field is built in large power motor startup firstly, in which DC pre-excitation is adopted and the rotor flux orientation is set to coincide with the center line of motor’s one phase winding. With the completion of this pre-excitation, the control strategy is switched to the vector control. The excitation subsystem and the torque subsystem in the motor can be decoupled dynamically after this pre-excitation and vector control. The experimental results show that the motor’s starting current rises smoothly and its output torque has fast response. This control strategy is capable of reducing the motor’s starting current peak and improving the safety of induction motor’s startup.