Audio-frequency powerline carrier control system with a current supervisory device
AssigneeSiemens Aktiengesellschaft
InventorsKarl Klausecker, Manfred Muller
Life of this patent
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Abstract
A power line control circuit receives audio-frequency signals from a pulsed inverter that is transformer-coupled to the power line. A filter circuit is connected between the inverter and the coupling transformer primary circuit to transmit the audio signals and prevent power line frequencies from reaching the inverter. A magnitude-measuring circuit determines when output current from the inverter exceeds a certain value and controls an intervening circuit to reverse, briefly, the state of conductivity of the inverter.
Claims8
In an audio-frequency powerline carrier control system to be connected to an N-phase alternating current powerline, comprising:
- an audio-frequency signal transmitter comprising a controllable inverter with three-phase outputs having an impressed d-c input voltage;
- a plurality of current transformers, in a delta configuration, each coupled to a respective phase output of said inverter to feed the transmitted audio-frequency signal in series into the alternating current powerline;
- filter circuits in parallel with the current transformers;
- an ignition control connected to the inverter and a pulse generator to form ignition control pulses for the inverter to cause the inverter to produce, during a predetermined transmission period, audio-frequency phase voltages at its respective phase outputs, said control including an intervention input for limiting the peak current in order to decrease the voltage time area of the audio-frequency phase voltage in response to an intervention command;
- monitoring means determining the phase currents between the inverter and filter circuit adapted to provide an intervention command if a predetermined current limit for the peak current is reached, the improvement comprising:
- the monitoring means including a monitoring device connected to each phase output for detecting when the associated inverter phase output current exceeds a threshold current of predetermined magnitude to thereby deliver separate intervention commands for each phase when the phase current exceeds the limit, independently of the other phase currents;
- and
- intervention control means, one for each phase, connected to a corresponding one of the monitoring devices for intervening in the control of the respective inverter phase in response to an intervention command from a respective monitoring device, said intervention control means adapted to apply a d-c voltage component to the respective inverter output phase by decreasing the voltage-time area of the inverter phase output voltage half-cycle whose polarity corresponds to the sign of the peak, as compared to the average voltage-time area of such a half-cycle in the case of non-intervention.
Dependencies are inferred from the claim text.