Operating Power

Three-phase ac is applied to the power isolation transformer to provide operating power to the regulated

power supply and the semiconverter power rectifier bridge.

When the generator is placed into operation, residual voltage will pass through the normally closed contacts

of K1. It is then rectified and applied to the generator field. When the generator output voltage builds up to

a sufficient value, K1 (connected across the output of the regulator power supply) energizes, and the

contacts open, removing the voltage build-up circuits. Thereafter, the power bridge output is established by

the gating pulses from the firing circuits. The minimum residual voltage required for build-up without flashing

is approximately 5% of nominal.

Flash and Overflash Protection (SSE 250 Series Only)

This circuit provides 125 Vdc to the generator field during start-up. When the generator output voltage rises

to 35% of nominal, the flashing voltage is removed and the static exciter regulator takes over. If the output

voltage does not build up in 25 seconds, the flashing voltage removed by the overflash protection circuitry.