Beechcraft 20138 - Theoryof Operation; Basic Requirements

SECTION III
-
THEORY
OF
OPERATION
3-1
BASIC
REQUIREMENTS
Aircraft
alternators,
in common with many
other
generators,
obtain
output current control
varying
the
current through a
separate
field
winding.
An
increase in field
current will
cause
an increase in
output
current.
The ratio
of field current to
output
current, for
a
given RPM,
is
known
as the
alternator gain. Typically,
an alternator
might have
a gain of
about
thirty
under average conditions; it
will be
seen
that
a relatively
small
change
in field current
will
cause a large
change
in
output
current.
Early
regulators
used
a
special
form
of
variable resistance
between
the
field terminal and the
battery
to control the current,
this
type is known
as a
carbon pile
regulator.
(Figure
3-1
below).
SERIES
ELEMENT
FIELD
ALTERNATOR
VOLTAGE
SENSING
00NTROL
ELEMENT
GROUND
FIG
3-1
VOLTAGE
REGULATOR
-
VARIABLE
RESISTANCE TYPE
3-1