Convertisseur de fréquence

摘要

1,111,021. Semi-conductor circuits. GENERAL ELECTRIC CO. 19 July, 1966 [13 Sept. 1965], No. 32358/66. Heading H3T. [Also in Divisions G3 and H2] A cyclo-converter having controlled rectifiers 18, 20, 22, Fig. 1, supplies a polyphase load 56 from a polyphase source 4 which may be a variable frequency generator. The controlled rectifiers are driven by " modulators " 12, 14, 16 which are arranged together with the blanking circuit 24 so that no firing signal is applied to any controlled rectifier when it is reverse biased. A reference oscillator 32 of fixed or variable frequency determines the output frequency, which is always less than the input frequency. The control circuitry for one controlled rectifier is shown in more detail in Fig. 3. Transformer 58 has its primary connected to the converter input. The voltage induced in winding I.P. of secondary 62 switches on transistor 98 when controlled rectifier AIP is forward biased to energize the modulator circuit 12, this includes pulse transformer 72, 68, 74 and silicon controlled switch 66 which is fired by a voltage 90 degrees displaced to the voltage in winding I.P. of secondary 62 derived from winding I.P. of the phase shifting secondary 64 combined with the reference voltage received at 86 and a bias voltage at 95. The reference oscillator and current limiting circuit are shown in Fig. 4. A signal proportional to the current to the converter is fed to the cathode-gate of the silicon controlled switch 116. The anode is connected to the output of the reference oscillator 134. If the converter current becomes excessive the silicon controlled switch fires and short-circuits the oscillator output for a few cycles until capacitor 132 becomes charged. After this the cathode-gate, anode-gate and anode act as an NPN transistor and convert the voltage regulator unit 140 to current regulating operations. In normal operation signals from the reference oscillator 134 and phase-splitter 136 are clipped at 138 to the magnitudes required for each phase by the voltage regulators which compare the output voltage received through lines 34, 36, 38 with the reference voltage across Zener diode 166. The clipped signals are fed to the modulators (Fig. 1) (through filters 142 if a sine wave output is required).