Short time emergency supply for frequency converter system - uses single synchronous machine with flywheel as energy store

摘要

During normal operation of the static frequency converters the synchronous machine, and its flywheel, runs as a motor connected to the converter bus-bar. The mains is connected via a solid state switch to the converter bus-bar. Mains interruptions, or major voltage depressions, are sensed by a logic unit. The bus-bar connector is put into the blocking mode and the machine goes over to the generating state, providing energy from its rotating mass to supply the converter loads. On restoration of the mains the machine is tripped, the converter rectifier sections blocked, and the connection between converter bus-bar and mains re-established. Subsequently, the converters are restored to normal operation and the machine reconnected. The converter interruption time on mains restoration is some 0.05 second. The motor stored energy is typically sufficient for maintaining converter output for 3 seconds. In the normal state the machine acts as power factor correcter for the converters. A typical application is to variable speed drives in synthetic yarn mfr.