Parallel Operation of VSCF Electrical Power Generators

The application of Variable speed Constant Frequency (VSCF) electric power generation systems has been limited to aircraft not requiring parallel operation of multiple channels. New applications in large multi-engine aircraft will require continuous parallel operation of installed channels to provide better system reliability and even loading of the generators. Parallel operation of VSCF equipment is similar in implementation to the familiar constant speed generator systems. The VSCF approach yields better overall performance than conventional systems due to inherent accuracies attainable with electronic power systems. Synchronous operation with precise phase angle control between channels is provided during either parallel or split modes of operation. Auto-paralleling of channels thus results in very small amplitude transients and virtually no frequency or phase angle transients on the bus. No Break Power Transfer (NBPT) from ground power or auxiliary power to aircraft power and vice versa result in minimal transients. This paper will treat the design philosophies and performance data of a production ready system as it relates to parallel operation and NBPT.