As a backup, the system accepts a secondary power input from a dc battery bank (125 to

250 Vdc nominal). The dc secondary input is diode-isolated and combined with the

3-phase diode bridge output. These sources energize the dc link, which is an unregulated

source voltage for the control output power through the IGBTs. The dynamic discharge

(DD) circuit limits the dc link voltage level during events such as load rejection or unit trip.

The converter output section uses IGBTs to pulse-width modulate the dc link source

voltage to its final value. The chopping frequency of the IGBTs is approximately 1.000

Hz. This output is fed to the exciter field as a regulated voltage or current. An output

shunt monitors the field current. Continuous dc output is provided up to 100% rating with

temporary forcing capabilities up to 210%. Regulated output flows through a dc contactor

to the exciter field.

The EX2100e Regulator system contains interface boards that are interconnected through

a high-speed serial link (HSSL) and cabled to their associated I/O terminal boards.