8.
If the input A.C. power is interrupted, the external battery feeds the load instantane-
ously through the Schottky Diode
D2
(
D2
will by-pass the resistors
R1
&
R2
). Voltage
available to the load will be approximately 0.4V lower than the battery voltage due to
forward voltage drop across
D2
.
Availability of AC power is signaled for remote monitoring through an opto-coupled
signal through the D-Sub connector (see page 5 under “Remote monitoring & Signal-
ing”). This signal may also be used to indicate that the load is being powered by bat-
tery (In case external battery is used for battery back-up).
When the input AC power returns, the battery will be isolated and the load current will
once again be supplied by the power supply. The discharged battery will recharge
through
R1
&
R2
(R1&R2 are in parallel offering a net resistance of 0.39 Ohm).
NOTE:
The value of charge limiting resistors is based on a typical 100AH deep cycle
marine battery. If a different type of battery is used, the value of the resistor should
be adjusted to meet associated charging requirements.
OUTPUT VOLTAGE ADJUSTMENT
NOTE : The voltages indicated are at no load and are measured at any of the module
output pads under S5 and S6 or at the DC bus before the Schottky Diode D1.
Parallel Operation Under Forced Current Share Control
The output voltage of each module
measured at the module output pads under
S-5 and
S-6
(See Fig.1) is
factory pre-set at 14.2 V
. A precision multi turn potenti-
ometer
VR1
is provided for fine adjustment of the output voltage of the module
(The adjustment range is 13.8 V to 14.6 V )
.
For the forced current share control to work properly, it is important that the output
voltage of each module connected in parallel is exactly the same. When 2 or more
modules are operating in parallel under forced current share control and if the output
voltage of any module is below 14.2 V, it’s current share control circuitry will not
function properly and it’s LED will start flashing. The LEDs of the other modules
which are putting out 14.2 V will remain continuously lighted and the output voltage of
the common DC bus (before the Schottky Diode
D1
) will be 14.2 V.
If the output voltage of any module is higher than 14.2 V, it’s LED will remain continu-
ously lighted but the LEDs of all the other modules will flash randomly. The output
voltage of the common DC bus (before the Schottky Diodes
D1
) will read the higher
voltage of this module.
Adjusting the output voltage of the modules at no load
NOTE :
The output voltage is adjusted by multi turn potentiometer VR1 ( Fig.1). As the
adjustment is very fine, multiple turns will be required even for small voltage change.
Turn clockwise for decreasing and anti clockwise for increasing
.
The adjustment range
is 13.8V to 14.6V
As explained under
OPERATION OF BATTERY BACK UP
on page 7, although the
output voltage at the module terminals
S5
and
S6
( Fig.1) or at the common DC bus
(before the Schottky Diode
D1
) is tightly regulated at the preset value of 14.2 V +/-
1%, the voltage at the output terminals
Load +
and
Load -
will vary between 14 V at
no load to 13.35 V at full load of 100 A due to the forward voltage drop of the isolat-
ing Schottky Diode
D1
and the drop along the DC bus and wiring.
