Design of an efficient starting circuit for LCI-fed synchronous motor drives

In this paper, after going through different starting schemes used in industry and literature to accelerate LCI-fed wound-field synchronous machines (WFSMs) from standstill, an efficient forced-commutation circuit is designed based on the field-oriented control strategy in stator flux reference frame. The proposed circuit can use SCR devices with current rating much smaller than that of the main switches. A complete explanation of the circuit operation and its parameters design procedure is presented. Then, simulation studies are conducted to verify the theoretical analysis and the results are compared with those of a common starting scheme. Comparisons show the superiority of the proposed circuit especially in terms of torque pulsations.