12 | SAMLEX AMERICA INC.
The voltage at the output terminals load + and load – will be as follows :
At no external load
approx. 14V
At 10A load
approx. 13.8V
At loads > 10A
approx. 13.8V minus 5mv per amp above 10A
when there is a requirement of un-interrupted D.C. Power to the load, an external
battery may be connected at the terminals b and battery –. when the input A.C.
Power is available, the load current is supplied by the power supply through isolating
Schottky Diode D1. At the same time, the battery is charged through resistors R1 & R2.
(These resistors will limit the maximum charging current to about 8 Amperes.)
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 9 under “Remote Monitoring & Signal-
ling”). This signal may also be used to indicate that the load is being powered by battery
(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).
SeCtION 9 |
Operation of Battery Back-up
R1
R2
D2
D1
NEGATIVE BUS BAR
POSITIVE BUS BAR
Battery -
B
Load +
Load -
R
LEGEND
D1, D2
Schottky Diode: 30V, 180A
R1, R2
Power Resistor: 0.78 OHM, 35W
R
Static Load Resistor: 120 OHM, 5W
Figure A
WARninG
the battery should be located in a well ventilated area to safely dissipate hydrogen gas
produced during the charging process.
