CS20.241, CS20.241-A1
C-Series
24V,
20A,
S
INGLE
P
HASE
I
NPUT
Preliminary
24.2.
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. The absorbing energy can be calculated according to the built-in
large sized output capacitor which is specified in chapter 6.
24.3.
E
XTERNAL
I
NPUT
P
ROTECTION
The unit is tested and approved for branch circuits up to 20A. 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.
24.4.
O
UTPUT
C
IRCUIT
B
REAKERS
Standard miniature circuit breakers (MCB’s or UL1077 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:
0.75mm²
1.0mm²
1.5mm²
2.5mm²
C-2A
29m
40m
56m
82m
C-3A
26m
35m
50m
77m
C-4A
21m
28m
36m
53m
C-6A
8m
10m
14m
25m
C-8A
4m
7m
11m
18m
C-10A
1m
2m
3m
6m
C-13A
-
-
-
-
B-6A
17m
24m
35m
53m
B-10A
12m
16m
23m
32m
B-13A
9m
13m
20m
29m
B-16A
4m
7m
9m
17m
MCB
Power Supply
AC
DC
+
-
+
-
Load
Wire length
S1... Fault simulation switch
S1
B-20A
1m
1m
2m
2m
*)
Don’t forget to consider twice the distance to the load (or cable length) when calculating the total wire length (+ and – wire).
Jan. 2012 / Rev. 0.5 DS-CS20.241-EN
Preliminary
All parameters are specified at 24V, 20A, 230Vac, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0 Germany
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