CP20.245-R2
CP-Series
24V,
20A,
S
INGLE
P
HASE
I
NPUT
Aug. 2022 / Rev 1.1 DS-CP20.245-R2 EN
All parameters are typ. values specified at 24V, 20A, 230Vac, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24.3.
B
ACK
-
FEEDING
L
OADS
Loads such as decelerating motors and inductors can feed voltage back to the power supply. This feature is also called
return voltage immunity or resistance against Back- E.M.F. (Electro Magnetic Force).
This power supply is resistant and does not show malfunctioning when a load feeds back voltage to the power supply.
It does not matter whether the power supply is on or off.
The maximum allowed feed-back-voltage is 35Vdc.
24.4.
E
XTERNAL
I
NPUT
P
ROTECTION
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.
24.5.
O
UTPUT
C
IRCUIT
B
REAKERS
Standard miniature circuit breakers (MCB’s or UL 1077 circuit breakers) are commonly used for AC-supply systems and
may also be 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 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. 24-4
Test circuit
Maximal wire length
*)
for a fast (magnetic) tripping:
MCB
Power Supply
AC
DC
+
-
+
-
Load
Wire length
S1... Fault simulation switch
S1
0.75mm²
1.0mm²
1.5mm²
2.5mm²
C-2A
34m
45m
64m
101m
C-3A
27m
36m
52m
79m
C-4A
19m
26m
35m
56m
C-6A
9m
12m
16m
23m
C-8A
4m
8m
12m
18m
C-10A
4m
6m
9m
15m
C-13A
2m
3m
4m
5m
B-6A
23m
30m
38m
67m
B-10A
11m
14m
21m
32m
B-13A
7m
12m
17m
23m
B-16A
4m
6m
8m
11m
B-20A
1m
1m
2m
4m
*) Don’t forget to consider twice the distance to the load (or cable length) when calculating the total wire length (+ and – wire).