INVERTER CONNECTION WITH BRIDGE FOR TRANSFORMING DIRECT CURRENT INTO SINGLE PHASE OR MULTIPHASE ALTERNATING CURRENT

摘要

A forced commutation defect, a simultaneous thyristor ignition, may occur for different reasons. The objective of the invention is to eliminate by a relatively simple solution the simultaneous ignition of thyristors caused by energy malfunctions, overloads, voltage variations at the input side etc. The objective is achieved, by means of a bridge connection at the inverter that transforms the direct current into an alternating current. The direct current entry point of this bridge has a main connection made up of the two controlled bridge branches connected in series having front end and rear end leads; and having at least a first half-bridge with a midpoint current outlet having a thyristor in each bridge branch; and with another, second half-bridge connected to the direct current entry connection, having two bridge branches connected in series and with a midpoint current outlet; and having an alternating current load and a control unit consisting of the control circuit for the bridge branches with at least one outlet for the control signal, and an ignition circuit for the ignition of the thyristors having at least one current entry and one current outlet, as well as a control unit containing the beat impulse generator that commands the control circuit through at least one outlet connector, that determines the frequency of the alternating current, the number of connectors corresponding to the number of phases and the phase angle being determined accordingly. For the control of the closing capacity of the bridge branches in the direction of the current flow there is provided a unit controlling the current extinction covering at a time one pair of connectors of the individual front end and rear end pole connectors of the two bridge circuits connected in series and connected at least to the first half-bridge permitting thyristor ignition, in a state of longitudinal disruption that impedes flow of current in the two controlled bridge branches connected in series, and in a state of longitudinal perfect connection of any of the bridge circuits of the control unit giving a command impeding the ignition of at least one of the thyristors of the bridge branches in disrupted state inthe direction of current flow; and, having a forced commutation extinction unit independent of the thyristor ignition, the control unit having the outlet connectors for the counter-phase extinction command that changes every half-period the electric signal level and that is synchronized with the signal of at least one outlet conector of the beat impulse generator for the independent forced commutation extinction unit per phase.