Self-commutated rectifier to improve line conditions

When thyristor rectifiers are used for electrical drives, reactive power is produced with fundamental and harmonic frequencies. Especially in single-phase traction lines, with their low short-circuit power, a technical solution of this problem, applicable mainly to thyristor-driven rail cars and locomotives, had to be found. In this paper, the sector-control system of a self-commutated unsymmetrical bridge is described. In the unsymmetrical half-controlled bridge connection, the two thyristors can be quenched by adding a self-commutating device. This attachment (supplement) can be applied to the single bridge or to two bridges in series (sector control). By using this self-commutating attachment, it is possible to shift the fundamental of the current to a leading angle with respect to the voltage. The resultant cos ÿ can be brought to unity or even to leading values.