Regulator Diagram (Lamar); Balancing Circuit Operation - Piper Navajo PA-31 Service Manual

BUS
PIPER NAVAJO SERVICE MANUAL
A967
ENCAPSULATED
CONTROL ASSY.
R
OPAR
CW4
FIELD
c
3
T
GND
Figure 11-33. Regulator Diagram (Lamar)
d. Thereafter, whenever alternator output voltage (as applied to the "BUS" terminal)
falls below the desired regulation value, the comparison transistor Q1 will supply increased
current to driver transistors Q2/Q3, which in turn will drive power transistor Q4 to a higher
value of field current. This will result in alternator output voltage increasing to a value
which will restore balance between the two voltages applied to Q1.
e. Conversely, if alternator output voltage (as applied to the "BUS" terminal) increases
due to a greater engine speed or reduced loading of the electrical system, the comparison
transistor Ql will act to reduce current flow to the driver transistors Q2/Q3, and thus
reduce the drive to power transistor Q4. This will result in a reduction of alternator field
current and automatically restore balance between the two voltages applied to comparison
transistor Q 1.
f. Capacitors C1 and C2 function, together with their related transistors, in a way to
smooth alternator output ripple and voltage spikes so that the alternator field current is
controlled at a steady value.
g. The LAMAR solid state regulator controls alternator field current to a steady value
as required by the electrical load conditions and engine speed. It does not continuously
switch field current between high and low values as do mechanical regulators and the
switching type of electronic regulators.
h. The design of this unit is such as to provide an alternator output voltage that does
not vary with ambient temperature.
1 1-46. BALANCING CIRCUIT OPERATION. (Considering two identical alternators and
regulators having the "PAR" terminals of the regulators connected.)
a. Balancing circuit operation is initiated within one regulator whenever individual field
voltages delivered by the regulator units to their related alternators are not equal.
Reissued: 10/12/79 ELECTRICAL SYSTEM
4C7