UC10.241, UC10.242
UC-Series
24V,
15A,
CAPACITOR-BASED
DC-UPS
23.
A
PPLICATION
N
OTES
23.1.
E
XTERNAL
I
NPUT
P
ROTECTION
The DC-UPS is tested and approved for branch circuits up to 50A. An external protection is only required, if the
supplying branch has an ampacity greater than this. If an external fuse is necessary or utilized, minimum requirements
need to be considered to avoid nuisance tripping of the circuit breaker. A minimum value of 20A B- or C-Characteristic
breaker should be used.
Check also local codes and local requirements. In some countries local regulations might apply.
23.2.
O
UTPUT
C
IRCUIT
B
REAKERS
The output of the DC-UPS is equipped with an electronic current limitation. An overload or short-circuit on the output
is electronically protected and cannot cause any harms, independent of which sizes of power supplies are used on the
input of the DC-UPS.
However, some applications require branch circuit or branch circuit conductor protection. Therefore standard
miniature circuit breakers (MCB’s or UL 1077 circuit breakers) are commonly used on 24V branches.
MCB’s are designed to protect wires and circuits. If the ampere value and the characteristics of the MCB are adapted to
the wire size that is used, the wiring is considered as thermally safe regardless of whether the MCB opens or not.
To avoid voltage dips and under-voltage situations in adjacent 24V branches which are supplied by the same source, a
fast (magnetic) tripping of the MCB is desired. A quick shutdown within 10ms is necessary corresponding roughly to
the ride-through time of PLC's. This requires high peak currents to open the circuit breaker in the required time.
Furthermore, the impedance of the faulty branch must be sufficiently small in order for the current to actually flow.
The following table has typical test results showing which C-Characteristic MCBs magnetically trip depending on the
wire cross section and wire length.
Fig. 23-1
Test circuit
Maximal wire length
*)
for a fast (magnetic) tripping:
0.75mm² 1.0mm² 1.5mm² 2.5mm²
22/27
C-2A
20m 25m 39m 58m
C-3A
12m 14m 24m 39m
C-4A
3m 3m 4m 4m
MCB
DC-UPS
Output
+
-
Load
+
-
Wire length
S1... Fault simulation switch
S1
*)
Don’t forget to consider twice the distance to the load (or cable length) when calculating the total wire length (+ and – wire).
23.3.
P
ARALLEL
U
SE TO
I
NCREASE
O
UTPUT
C
URRENT
Do not use the DC-UPS in parallel to increase the output power.
May 2016 / Rev. 2.2 DS-UC10.241-EN
All parameters are specified at 24V, 10A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0 Germany
