Study on Large Asynchronous Motor Starting Check for Auxiliary Power System

Large-capacity 600 MW air-cooling units and 1000 MW thermal generators are being incorporated into power system in China. As a result, demands for large-capacity, high voltage grade plant motors are increasing. However, large-capacity motors usually cause voltage fluctuations, hence undermining reliability and stability of the entire power plant. Therefore, analyzing motor starting in large-capacity asynchronous motors of auxiliary power system is crucial. Characteristics of large-capacity motors in their self-starting, self-starting in series and self-starting in group are examined, as well as effects of locked-rotor current factor on starting current, bus voltage and terminal voltage in motor starting. Then calculations about starting voltage under different start-up modes are presented. Simulations are conducted on starting of large-capacity motors in a 1000 MW unit as the locked-rotor current factor runs from 4 through 6.5. Comparisons of theoretical calculation and simulation results verify the correctness of setting locked-rotor current factor at 4.