TM 11-6130-266-15
The voltage of a battery to be charged is indicated prior
capacitors A8C2 through A8C5 is controlled by varying
to the application of ac power. The post regulator is
the firing angle of SCR's A4Q1 and A4Q2. This is
designed so that if the ac power is turned on after
accomplished by interposing self-saturating magnetic
connecting the output to a reverse polarity source
amplifier A4A1L1 between gate generator A4A2,
(exceeding 8 volts), the transfer control will lock out, and
A4A1T1, and the SCR gates. Net dc control winding
no output current will flow. Filter network FL2 is used to
current determines the phase angle. A short circuit
eliminate radio-frequency interference.
stabilizing winding provides magnetic amplifier gain
relatively independent of core characteristics
(temperature). This shunting reduces the frequency
4-2. Circuit Description
dependence over the range of 47 to 450 Hz to an
a. Input Power. The power supply receives 115 or
insignificant level. The series pass element voltage drop
230-volts ac power from the line via AC INPUT
is compared to a 2.0-volt dc reference, closing the loop.
receptacle J3 and AC circuit breaker CB1. The ac is
Free-wheeling diode A3CR4 and choke L1 prevent input
then routed through 230V-115V selector switch S1 to
current spiking, high-peak voltages, and excessive
transformer T1. Secondary winding 9-10 energizes AC
capacitor ripple current, while diode A3CR6 provides
indicator lamp DS1. From secondary winding 9-11, 42V
overvoltage protection when the voltage exceeds 36
ac is fed to auxiliary supply and control assembly Al
volts.
where it is converted to 16 and 32 volts do. The 32V de
d. Series Pass Element . The series pass element,
output of Al energizes relay A1K1 which, in turn applies :
comprising pass driver A3Q1 and series pass stages
32V de to the coil of transfer relay A6K1 via closed
A3Q2 and A3Q3, maintains a constant voltage or current
contacts 7-10 of A1K1. Energizing A6K1 connects the
output by receiving inputs from the voltage and current
output of the power supply, via contacts 2-4 of A6K1, to
sensing circuits. The dc voltage from the preregulator
DC OUTPUT receptacle J6 and DC OUT receptacle J7.
passes through a conventional triple Darlington series
Simultaneously, NORM indicator lamp DS2, which is
regulator element, consisting of pass driver A3Q1, series
connected across the coil of AGK1, goes on indicating
pass A3Q2, and pass driver A2Q1, before reaching the
the power supply is producing a normal do output
output. The series pass element is programmed by the
voltage.
voltage and current controls. Since the series pass
b. Transfer Control. A Schmitt trigger, comprising
element acts as a variable resistor, changes in the ac
input level detectors A1Q5 and A1Q7, senses line
input voltage are reflected across the element, enabling
voltage through auxiliary power supply rectifier diodes
it to maintain a constant output voltage.
A1CR1 through A1CR4. Switching occurs when the ac
e. Temperature Control. Temperature sensing
input power fails completely or when the input voltage
switch A3S1 controls the ac line voltage applied to
falls to 90 volts rms nominal (or 180 volts rms nominal
transformer A4A1T1 winding 1-2. This in turn, supplies
for a 230-volt input).
the ac power required to operate squaring gate
Relay driver A1Q9 is cut off causing relay A1K1 to drop
assembly A4A2. If the operating temperature of the
and deenergize relay A6K1. Deenergized contacts 4-1
power supply exceeds a maximum safe value, the
of A6K1 then switch the load to the external battery
sensing switch opens and disconnects power to A4A2.
connected at BATTERY in receptacle J8, and EMER
This action shuts down the power supply.
indicator lamp DS3 is energized. This action insures
Although AC indicator lamp DS1 remains on, the NORM
that there is no interruption of de power being furnished
indicator lamp DS2 goes out, indicating there is no dc
to the load.
output. The sensing switch closes automatically when
Both the AC and NORM indicator lamps go out as soon
the operating temperature falls to a safe value.
as battery power is connected to the load.
f. Comparator. The transient suppressor
EMER indicator lamp DS3 remains on until normal ac
comparator stage is A5Q3. The comparator has the
input power is restored, at which time the load is
following functions: it compares the voltage drop across
automatically returned to the power supply.
the series pass element to a reference within the
c. Preregulator and Control. The preregulator
comparator to maintain the 2.5-volt drop across the
circuit isolates the series pass element from input line
series pass element; it furnishes a compensation signal
variations. To maintain high efficiency, the voltage drop
to magnetic amplifier A4A1L1 so that the 2.5 voltage
across the series pass element is maintained at 2.5 volts
drop across the series pass element may be increased
(nominal) under all loaded output voltage or current
to 4 volts, when a no-load condition is indicated
conditions. The net de voltage in filter
4-2 Change 1
