Puls UC10.241 DIN-Rail UPS Specification Guide
UC10.241, UC10.242
UC-Series
24V,
15A,
C
APACITOR
-
BASED
B
UFFER
M
ODULES
22.9. W
HAT DO
KJ
AND
KWS
MEAN
?
The units kJ (kilo Joule) or kWs (kilo Watt seconds) is used for specifying the installed storage capacitor size.
1 kJ = 1 kWs = 1000Ws
The stored energy of a capacitor can be calculated with the following formula:
Energy ( Ws ) =
C *U
2
2
For example: A 350F (Farad) capacitor which is charged to 2.5V has the following energy
26/27
*
2
.
5
E
= 350F
V
2
2
=1093
Ws = 1
.
09
kWs
E =
C * (U1
2
−U2
2
)
During discharging of the capacitor, the voltage decreases with the amount of discharge. A boost converter is needed
to generate a stable output voltage. The boost converter needs a minimum input voltage (cut-off voltage), which
reduces the amount of energy. The cut-off voltage usually depends on the load current, the lower the load current,
the lower the cut-off voltage.
Considering this voltage range, the energy can be calculated with the following formula (full charge voltage= U1=
2.5V, cut-off voltage= U2= 1V):
to generate a stable output voltage. The boost converter needs a minimum input voltage (cut-off voltage), which
reduces the amount of energy. The cut-off voltage usually depends on the load current, the lower the load current,
the lower the cut-off voltage.
Considering this voltage range, the energy can be calculated with the following formula (full charge voltage= U1=
2.5V, cut-off voltage= U2= 1V):
=
350* (2.5
2
−1
2
)
= 919Ws = 0.92kWs
2
2
The energy which can be used for the 24V loads is further reduced by the efficiency of the boost converter.
The UC10.241 has a rated capacitor size of 6kWs and the UC10.242 12kWs. This is the energy which can be used for
24V load at low load currents.
24V load at low load currents.
Calculation of the needed energy:
Example: A power of 45W is needed for 2 minutes:
= 45
= P *
E
t
W * 120 s = 5400Ws = 5 .4 kWs
Always check with the buffer time curve (see Fig. 6-1) if the load
can be powered for the required period of time!
Apr. 2014 / Rev. 2.0 DS-UC10.241-EN (REVC)
All parameters are specified at 24V, 10A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
All parameters are specified at 24V, 10A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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