Piper SEMINOLE PA-44-180, Maintenance Manual

Page: 226 / 881

LAMAR MODEL NO. B-00392-1 VOLTAGE REGULATOR OPERATION
1. The Lamar no. B00392-1 voltage regulator delivers a pulse width modulated field control output, as
required, to maintain the alternator output voltage.
2. An overvoltage protection is incorporated, which latches off regulator output following an overvoltage
event.
3. The regulator is protected against damage due to output (field) short to ground. A short will latch off
the output until reset.
4. Momentarily turn OFF 14 Volt power supply to reset latch off caused by either an overvoltage or
shorted output.
5. Field pulse rise and fall times are slowed to be more that 50 microseconds.
6. Refer to Figure 24-8 to check overvoltage operation. Temporary indicator will be activated when
overvoltage circuit locks out. (See CAUTION.)
7. In an operating system (2 units with equalizer connection), an excess current in one shunt, due to an
overvoltage condition in that side, will cause the opposite side overvoltage sensing to be desensitized.
The side causing the overvoltage will be selectively tripped. Excess shunt current will then fall to
zero, which permits the normal side overvoltage sensitivity to restore to its calibrated value.
8. Except for the equalizer connection, the left and right alternator systems are independent of each other.
The equalizer connection will NOT cause a failure in one system to disable the other normal operating
system.
9. The equalizer circuit may be faulted to either ground or the bus with no damage to either system.
Balancing action and selectivity of the overvoltage trip protection will be lost. If the equalizer faulted
to the bus, system voltage will increase to the limit of balancing circuit control authority (less than 1
Volt). The overvoltage operating point of both systems will be elevated to the value provided for
selective trip action (approximately 2 Volts above the normal overvoltage trip calibration point).
Figure 24-8. Lamar 00392-1 Regulator Overvoltage Test Method
ADJUSTING VOLTAGE REGULATOR UNIT. (LAMAR MODEL NO. B-00392-1)
The only adjustment necessary to maintain the alternator system is the adjustment of the voltage control on
the voltage control unit. A voltage of 14 volts dc is automatically maintained. All other adjustments are made
at the time of installation and need not be reset.
— CAUTION —
IN-AIRCRAFT TESTING WITH ALTERNATOR RUNNING IS NOT
RECOMMENDED. DO NOT BYPASS REGULATOR BUS TO FIELD AS A
MEANS OF CHECKING ALTERNATOR WITH ALTERNATOR RUNNING.
PIPER AIRCRAFT
PA-44-180/180T
AIRPLANE MAINTENANCE MANUAL
24 -23-10
Page 24-22
Revised: June 20, 1995
1J10
PURE D. C.
REGULATED
SUPPLY
PRECISION
V/M
B-00392-1
REGULATOR
IND.
RED BLUE
+
-
PTT
BLACK
TEMPORARY INDICATOR. USE A 28 V
B U L B O R A R E L A Y . N O O T H E R
CONNECTIONS ON THE BLUE CIRCUIT
DURING THE TEST PROCEDURE