Detailed Circuit Description

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

a. Input Power Ciircuit (fig. FO-1). The input

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