two durations of gate pulse. For example, for gating
angle 10 degrees and duration of the gate pulse
600pec, 92% of the time, when it is possible to
restore charge, is used to charge storage capacitor
on SSGD. For the same gate pulse duration, but
larger firing angle, the percentage of this time used to
restore voltage on storage capacitor is lower. Fig. 8,
also shows the percentage of total turn off time when
is possible to restore charge on storage capacitor. It
is clear that full SCR turn off time is possible to use to
restore the charge only for firing angle greater than
90 degrees.
The initial charge on capacitor Cgl is obtained from
the power frequency voltage across the SCR's during
the short time (approximately 70ms for storage
capacitor 660u9 between voltage being applied , and
initiation of gating the SCR's. Fig. 9 shows variation
of the charge time versus value of storage capacitor
for 2300V. The capacitor voltage drop during the turn
on of the SCR is given at Fig. I O .