Precise frequency power generation from an unregulated shaft

A system for generating precise frequency power from an unregulated shaft is described. The system comprises a high-frequency variable-speed generator, a semiconductor frequency changer, an output filter, and a voltage and frequency regulator. The semiconductor frequency changer employs silicon p-n-p-n switches as the power handling components. The operation of a typical frequency changer is described, and an oscillogram is presented which verifies the performance. Also, the ability of the frequency changer to supply a lagging reactive load is illustrated. The generator described is a brushless Secsyn type. The rotor of this machine has no rotating exciting windings and is of tubular steel construction which permits very-high-speed operation. This results in a lightweight system. Voltage regulation is accomplished by controlling both the frequency changer and the excitation of the generator. This improves speed of response. The frequency regulator is open-loop with a frequency transient that is no more than wave distortion. The accuracy of the system frequency is determined entirely by the accuracy of the frequency reference which can be as high as 0.001%. Application of the system to emergency power systems, auxiliary power systems, and secondary power systems is mentioned.