Beechcraft 20138 - Block Analysis

3-2
BLOCK ANALYSIS
Figure
3-3
shows
a
simplified block
diagram of the
voltage
regulating
portion of the
Model
20138.
This portion contains a
parallel
voltage
sensing
circuit,
involving
transistors
Q3,
Q4 and
QS,
and a series
switching
circuit,
involving transistors
Q6
and Q7.
SERIES
B
FROM
+
28V
S#ITCHING
BUSS CIRCUIT
Q6
-
Q7
TO FIELD
VOLTAGE
REGULATOR
SENSING
VOLTS
CIRCUIT
ADJUST.
Q3
-
Q4
GROUND
FIG.
3-3
BLOCK DIAGRAM
-
REGULATOR
Operation:
If the
aircraft buss
voltage
is
below
the preset
level
(regulator
voltage
adjust) the series
switching
circuit will
close.
This
action
causes current to
flow from
the battery
through the field
winding
to ground.
If the alternator has a
gain of thirty,
then
thirty
times this
current will flow
into the battery, causing
its voltage to
increase.
3-5