DC motor thyristor control system - permits supply level to be reduced to near zero using auxiliary thyristor

摘要

A DC Supply control is esp used for regulating the speed of a motor. It uses main (Th1) and auxiliary (Th3) thyristors which allow the power supply level to be reduced to a value close to zero and the duration of each current excursion from zero to be varied. The main switching thyristor is in parallel with an extinction thyristor itself in series with an inductance and capacitor, the total circuit including a parallel starter diode. An auxiliary thyristor (Th3) is connected in series with the thyristor (Th2) controlling extinction and is triggered at the same frequency. Alternative arrangements allow this auxiliary thyristor to be mounted in series with that controlling the main switching line.