method of generation of polyphase sinusoidal current adjustable frequency, device for implementing the method, and application of this method to the control of a static converter

摘要

1,093,218. Converting. J. VERMOTGAUD. Sept. 20, 1965 [Sept. 22, 1964], No. 39978/65. Heading H2F. An N-phase sinusoidal voltage of variable frequency and amplitude is generated from a single-phase sinusoidal voltage of variable amplitude and an N-phase rectangular voltage. Each phase of the polyphase voltage modulates a voltage from the sinusoidal input, and filters extract from the modulated signals the components having a frequency equal to the difference of the two input signals. The output frequency is varied by varying either input frequency, and the output amplitude depends on the amplitude of the sinusoidal input. In an embodiment the apparatus provides an output R, S, T (Fig. 4) which controls an inverter supplying an induction motor. The single-phase input 20 is fed to the parallelconnected primaries of transformers 40 in the modulators 25, 26, 27. Each phase of the threephase input 21 controls a pair of transistors 42, 43 connected to the secondary windings as shown. The inputs 20, 21 may be derived from a single oscillator through conventional frequency dividing and waveform changing circuits (Fig. 5, not shown).