Over Temperature Protection - Samlexpower SEC-1223BBM Owner's Manual

Switch mode dc power supply with battery backup

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Table of Contents

SeCtIOn 4 |

Battery Backup Function is Used - external Battery is connected

If the load tries to draw current higher than the current limit value of 25A of the Power

Supply Section, the output voltage of the Power Supply Section will not be regulated

and the voltage at the Load Terminals (3, 4) will drop. Portion of overload current

beyond 25A will now be fed from the battery and the battery will start draining at this

differential current. for example, if the overload current was 40A, the Power Supply Sec-

tion will provide 25A and the battery will provide the balance 15A. The battery will start

draining at 15A. The voltage at the Battery Terminals (5, 6) will start dropping and will

be equal to the voltage corresponding to its actual State of Charge. The voltage at the

Load Terminals (3, 4) will be around 0.3 ± 0.1V below the voltage at the Battery Termi-

nals (5, 6). External 25A fuse (f2) on the load side will blow only on sustained current

≥ 25A for > 100 sec but will not blow at higher short duration surge currents deter-

mined by its Time Current characteristics. for example, based on the Time Current

Characteristics of 32V, 25A fuse Type ATC-25 from Cooper Bussmann, the fuse can pass

extremely high currents for shorter durations is as follows:

•

550A for 10 ms

•

170A for 100 ms

•

40A for 1 sec

•

25A continuous (for > 100 sec)

In case of short circuit on the load side, the external 25A fuse (f2) on the load side will

blow because of very high additional current supplied by the battery (Additional battery

current supplied into the short circuit on the load side = Short circuit current - 25A from

the Power Supply Section). for example, if a short circuit current of 170A tries to flow

for > 100 ms, 25A will be supplied by the Power Supply Section and the balance 145A

will be supplied by the battery. As the external 25A fuse (f2) on the load side will see

170A and the external 25A fuse (f1) on the battery side will see 145A, the external 25A

load side fuse (f2) will blow first.

PRotection AGAinSt ReVeRSe PoLARitY oF BAtteRY connection

In case of reverse polarity of battery connection, internal Diode connected across the

battery output terminals will be forward biased and the external 32V, 25A battery side

fuse (f1) will blow.

cAUtion!

reversal of polarity may result in permanent damage to the unit and to the load.

DAMAGe DUe to ReVeRSe PoLARitY iS not coVeReD UnDeR WARRAntY.