Generating adjustable, phase-fixed thyristor ignition pulses - comparing max. values of sawtooth voltage flanks with reference voltage

摘要

The ignition pulses are generated for a grid control set of a polyphase rectifier or inverter with thyristors. The pulses are generated by smoothing the synchronisation mains voltage and generating rectangular pulses corresponding to the frequency of the smoothed mains voltage. Time-linear rising sawtooth voltages are generated, with starting points derived from the rising flanks of the rectangular pulses. A control voltage is compared with the flanks of the sawtooth voltages for deriving of ignition pulses from intersection points of the control voltage with the flanks. The max. values of the flanks of all time-linear rising sawtooth voltage are compared with a single reference voltage. When the latter has been exceeded the sawtooth voltages are reduced to its value, while they are raised to this value when being below the reference voltage.