Figure 1-29.-Power circuit.

Figure 1-29.-Power circuit.

and voltage spikes. Controlling the point during any

positive with respect to cathode, and a trigger pulse is

applied to terminals A and B. SCR1 will conduct current,

applied half cycle of ac voltage that the trigger pulse is

and SCR2 will block current like a normal rectifier bridge,

applied to the gate of the SCRs makes it possible to

for the remainder of the applied half cycle, as shown in

control the output power of the dc power supply.

The signal developed in the power section of the

figure 1-29. Diode D1 and thyrector SP1 (a General

voltage regulator (fig. 1-27) is used as dc control current

Electric silicon controlled diode used for ac surge

to the static exciter.

protection) are used to protect the circuit from transients

1-25