Datasheet

CPS20.121
C-Series
12V, 30A, SINGLE PHASE INPUT
22.3. EXTERNAL INPUT PROTECTION
The unit is tested and approved for branch circuits up to 30A (UL) and 32A (IEC). An external protection is only
required if the supplying branch has an ampacity greater than this. Check also local codes and local requirements. In
some countries local regulations might apply.
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 10A B- or C-Characteristic breaker should be used.
22.4. OUTPUT CIRCUIT BREAKERS
Standard miniature circuit breakers (MCB’s or UL 1077 circuit breakers) are commonly used for AC-supply systems and
may also be used on 12V 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 12V 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 power supplies with high current reserves and large output capacitors.
Furthermore, the impedance of the faulty branch must be sufficiently small in order for the current to actually flow.
The best current reserve in the power supply does not help if Ohm’s law does not permit current flow. The following
table has typical test results showing which B- and C-Characteristic MCBs magnetically trip depending on the wire cross
section and wire length.
Fig. 22-3 Test circuit
Maximal wire length
*)
for a fast (magnetic) tripping:
0.75mm² 1.0mm² 1.5mm² 2.5mm²
C-3A
9m 12m 18m 26m
C-4A
7m 10m 14m 22m
C-6A
4m 6m 10m 14m
C-8A
3m 5m 8m 12m
C-10A
3m 4m 7m 10m
B-6A
8m 11m 14m 24m
B-10A
5m 7m 10m 17m
B-13A
4m 6m 9m 14m
B-16A
3m 5m 7m 11m
MCB
Power Supply
22/26
AC
DC
+
-
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).
Apr. 2014 / Rev. 1.4 DS-CPS20.121-EN
All parameters are specified at 12V, 30A, 230Vac, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone [phone] Germany