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Apparatus for converting a multiphase alternating current with variable frequency into a multiphase alternating current with fixed, lower frequency.
Apparatus for converting a multiphase alternating current with variable frequency into a multiphase alternating current with fixed, lower frequency.
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机译：用于将具有可变频率的多相交流电转换为具有固定的较低频率的多相交流电的设备。
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1352949 Control of cycloconverters GENERAL ELECTRIC CO 19 April 1971 [11 March 1970] 23746/71 Heading H2F In a cycloconverter having feedback from the output to the gate control circuits for the main converting element, the feedback is arranged to be reduced as a function of output current and power factor so as to reduce the likelihood of mis-commutation of the main converting elements when operating on loads of poor power factor. Fig. 1 (not shown) relates to a block diagram of a three-phase cycloconverter comprising six groups of three thyristors arranged to convert the varying frequency output of an aircraft generator 10 into a constant 400 Hz output. The gate circuits of the thyristors are controlled in dependence on the output from a three-phase reference oscillator which feeds gating circuits or modulators with control pulses, the phase of which is determined by feedback circuits which may provide voltage regulation, wave shape correction or to minimize D.C. components. Each phase may have a feedback loop 88 including a twin T filter 30 arranged to block the 400 Hz fundamental and, after combination with other feedback loops in an operational amplifier 90, is fed to a modulator (not described in detail) controlling a pair of antiparallel groups of thyristors. The Specification describes with the aid of Figs. 6 and 7 (not shown) that for a given power factor load, the graph of input current against output current reaches a minimum at approximately half load. A signal dependent on power factor can thus be determined by monitoring the input current by means of transformers 60, 61, 62, the outputs of which are rectified so as to provide a negative going signal across capacitor 67. At low power factors, this signal will be less negative than the reference voltage across a Zener diode 93 so that a corresponding signal will be provided at the collector of transistor 97 which is added to a further signal from the common point of rectifiers 72... 74 which is proportional to load current. Field effect transistor 76 is shunted across the feedback loop 88 and is arranged to reduce the feedback if the output current is 1À25 times the rated value at unity power factor and at progressively lower currents at lower power factors, reducing to 0À5 times the rated load current at the zero power factor. The reduction in feedback is stated to reduce the likelihood of mis-commutation of the main converting elements.
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