Regulated Single-Phase Rectifier Circuit Solutions and Their Impact on Power Coefficient

Locomotive electric drives with DC commutator motors and smooth voltage regulation systems usually apply reversible power rectifiers based on partially or fully controllable semiconductor devices. The paper presents theoretical analysis of working processes of different single-phase bridge circuits. Reviewed circuits include: initial (or type) half-period thyristor-based circuit; asymmetrical circuit with two thyristor arms and two diode arms; half-period thyristor circuit with a shunting diode arm in parallel with the rectified subcircuit; contemporary transistor-based bridge circuit. Detailed time diagrams of working processes of the circuits demonstrate that application of different schematic solutions and new control algorithms allows for a significant decrease or complete elimination of phase shift between current and voltage curves on AC side of the electric drive (i.e. power transformer primary winding), making it possible for power coefficient of the rectifier to increase up to a maximum of 1.