2
magnetized, it creates a back e.m.f. across the gate
winding, limiting current flow. As magnetism of the
core increases, the rate of change in flux decreases,
resulting in a decrease in back e.m.f. This action
continues until the core becomes fully magnetized
(saturation). At this point no further change in flux
density occurs. Resistance across the gate winding is
then limited by the series resistance of the gate
winding and field winding, and current flow is maxi-
mum. Control and regulation are accomplished by
resetting the core of the magnetic amplifier at some
point below saturation during the half-cycle the gate
winding is not conducting. This is done by applying dc
control current to magnetic amplifier control winding
(C1-C2) and is referred to as magnetic reset or bias.
Increasing the control current resets the magnetic
amplifier core further below saturation. The further
the core is reset below saturation the more back
e.m.f. will be present across the gate winding. Thus,
the less current will flow through the gate winding and
exciter field. The magnetic amplifier reacts in an
opposite manner when control current is decreased.
E. Stability
The voltage regulator includes a negative feedback
system stability circuit designed to prevent oscillation
(hunting) of the generator output voltage. The circuit
consists of capacitors C2, C5, resistors R5, R6, R16
and a stability adjust potentiometer R7 .
F. EMI Suppression
Filter RFI is included in the voltage regulator input
power circuit to reduce conducted EMI to negligible
levels.
G. Test Voltage (optional)
A dc voltage proportional to the set sensing voltage is
available at terminals A and F- as an option.
