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Buffer Block


Prevents Equipment Stoppage, Data Loss,and Other Problems Resulting from Momentary Power Failures


Model S8T-DCBU-02
Input Voltage 24 to 28 VDC
Current Charging 0.4 A
Standby 0.18 A
Output voltage For 24 V: 22.5 V typ., 22.0 V min.
For 28 V: 26.4 V typ., 25.8 V min.
Output current 2.5 A
Backup time
Time required until the voltage drops from the fully charged level down
to 21.6 VDC
1,000 ms min. (for an output current of 1.2 A)
500 ms min. (for an output current of 2.5 A)
READY indicator Yes (color: green)
READY output Yes (relay: 24 VDC, 0.1 A max.)
Backup indictor Yes (color: red)
Backup output Yes (relay: 24 VDC, 0.1 A max.)
Overcurrent protection Reverse-L dropping, automatic reset, overcurrent detection point:
5.8 to 6.8 A
Overvoltage protection Yes
Parallel operation Yes (Up to 4 Blocks)
Series operation No
Other Ambient operating
Refer to the derating curve in Engineering Data. (with no condensation
or icing)
Storage temperature -25 to 65°C
Ambient humidity Operating: 25% to 85%; Storage: 25% to 90%
Dielectric strength *4 1.0 kVAC for 1 minute (between all DC connection terminals and PE
terminals; Detection current: 20 mA)
500 VAC for 1 minute (between all DC connection terminals/PE
terminals and all signal output terminals; detection current: 20 mA)
Insulation resistance 100 MΩ min. (between all DC connection terminals and PE terminals)
at 500 VDC
Vibration resistance *5 *6 10 to 55 Hz, 0.375-mm single amplitude for 2 h each in X, Y, and Z
Shock resistance *5 *6 150 m/s2, 3 times each in ±X, ±Y, and ±Z directions
EMI Conducted
Emission *5
Conforms to EN61204-3 EN55011 Class B and based on FCC Class A
Conforms to EN61204-3 EN55011 Class B
EMS Conforms to EN61204-3 High severity levels
UL: UL508 (Listing; Class 2: Per UL1310) *7
cUL: CSA C22.2 No.107.1 (Class 2: Per No. 223) *7
EN: EN62477-1
SEMI SEMI F47-0200
Weight 450 g max.

Reference Value

Item Value Definition
Reliability (MTBF) 135,000 hrs min. MTBF stands for Mean Time Between Failures, which is calculated according
to the probability of accidental device failures, and indicates reliability of devices.
Therefore, it does not necessarily represent a life of the product.
Life expectancy 10 yrs. min. The life expectancy indicates average operating hours under the ambient
temperature of 40°C and a load rate of 50%.
Normally this is determined by the life expectancy of the built-in aluminum
electrolytic capacitor.