This is a 180 ° turn-on type, each thyristor in the resistive load conduction 180 ° per cycle, adjacent thyristor two trigger pulse interval of 60 ° commutation carried out in the same bridge arm, Such as a phase VT1 and VT4, b phase VT3 and VT6, c phase VT5 and VT2. At any moment in each cycle there is a tube on each phase. In order to ensure a reliable inductive load ...