Bus transfer of multiple induction motor loads in a 400 megawatt fossil power plant

A computer model capable of simulating multiple induction motors during bus transfer is described and its results compared with field tests. Optimum switching times are specified based on bus residual voltage and phase angle that will maintain motor inrush currents below ANSI/NEMA criteria. Recent papers have documented the inadequacy of the ANSI/NEMA resultant V/Hz criteria for assuring that motor-shaft torques remain below acceptable levels following bus transfer. The presented results support these findings, but indicate that the combination of high and low-inertia motors fed from the same bus will reduce motor peak-shaft torques when compared to individual transfer of low-inertia motor/pump units alone