TM 11-6130-381-14
through the collector of Q6103 and CR6116, so
UJT B1 to B2 voltage (Vbb), through R6122 and
that the beginning of the charging cycle in the
CR61 15, until it reaches the emitter peak voltage
UJT emitter circuit is controlled by a pedestal
(VP), and whereupon the UJT fired. The trigger is
voltage derived from the current flow in the
then coupled to the silicon-controlled rectifier
battery-charging path.
(SCR) goes through pulse transformer T6101,
e. Figure 4-4 shows waveforms in the trigger
firing the SCR whose anode-to-cathode voltage is
circuit. At the beginning of each cycle, the clipped
positive. Diode CR6129 (fig. FO-1) clamps the
sine wave rises to its maximum voltage, and C6114
base of the trigger pulse. The other SCR anode
circuit is reversed by bias due to the bridge
is brought rapidly to the pedestal voltage by the
arrangement and, therefore, does not conduct.
collector circuit of Q6103 and CR6115 (fig. 4-1).
Capacitor C6114 continued to charge toward the
f. The time at which the UJT fires is controlled
SWITCH S6002 has a switch guard that must be
by the pedestal voltage. As the pedestal voltage
loosened to set the SELECTOR SWITCH S6002
increases, the time required for the capacitor
to 115 V (switch guard pushed down), or 230 V
voltage to reach the emitter peak voltage (VP) is
(switch guard pushed Up). For ll5-volt ac input
decreased; as the pedestal voltage decreases, the
power operation, when SELECTOR SWITCH
time is increased. Changes in current flow in the
S6002 is set to 115V, the two primary windings of
b a t t e r y - c h a r g i n g path are felt at R6003 and
transformer T6001 are connected in parallel. For
produce an error signal at the input of differential
230-volt ac input power operation, when
comparator A6102 that causes a corresponding
SELECTOR SWITCH S6002 is set to 230 V, the
change in the pedestal voltage. This, in turn,
two primary windings of transformer ml are
changes the firing angle of Q600l and Q6002, and
connected in series. POWER ON indicator light
reduces the error signal and maintains a constant
DS6001 is connected screws one set of the primary
c u r r e n t flow in the battery-charging path.
windings of the transformer and illuminates to in-
R e s i s t o r s R6005 and R6006 provide trigger
dicate the presence of input power when AC POWER
isolation.
switch S6001 is set to ON, and power interlock
switch S6005 is actuated. CIRCUIT BREAKERS
4-2. Detailed Circuit Description
CB6001 and CB6002 provide circuit protection in the
event of short circuit or overloads. Although the
power circuit comsists of the ac power input cable
chassis is grounded to the input power source
and connector P6001, filter FL6001, capacitor
ground, the internal circuity of the battery charger
C6003 and C6004, power interlock switch S6006,
is referenced to the negative terminal of the battery
bleeder resistors R6011 and R6012, AC POWER
being charged for a floating ground. The returns of
s w i t c h S6001, SELECTOR SWITCH S6002,
all internal power sources are referenced to this
C I R C U I T BREAKER CB6001 and CB6002,
floating ground. Resistors R6011 and R6012 are
POWER ON indicator light DS6001, and power
s a f e t y bleed resistor for filter FL6001 and
transformer T6001. Power interlock switch S6005
capacitors C6003 and C6004. E l e c t m a g n e t i c in-
is actuated when the chassis is installed in its case,
terference suppression of the input power line is
and interrupts one leg of the input ac power when
the chassis is removed from its case. SELECTOR
4-4
