Basler Electric MVC301 - Manual (Page 5)

2-1
SECTION 2
PRINCIPLES OF OPERATION
2-1. GENERAL
a. The Electronic Manual Voltage Control (MVC-301) is a phase-controlled, silicon-controlled,
rectifier (SCR) bridge. By adjusting the external MANUAL VOLTAGE ADJUST control, the firing
angle of the SCR change providing an adjustable voltage level to the exciter field.
b. During start-up, the build-up circuit holds the SCRs power bridge at maximum output. When the
voltage has built-up to approximately 30 Vac, the internal build-up circuit relinquishes control to the
external MANUAL VOLTAGE ADJUST.
c. The AUTO-OFF-MAN voltage control mode switch allows transfer from the voltage regulator to
the Manual Voltage Control or from Manual Voltage Control to voltage regulator. A free wheeling
diode remains connected to the field to allow safe switching without arcing.
d. The MVC-301 is designed to operate from 120 or 240 Volt nominal sources without any electrical
changes such as tap selection or terminal connections. Taps are provided to select 32, 63, or 125
volt maximum outputs.