CP20.241-R1, CP20.241-R2,

CP20.241-R3

CP-Series

June 2017 / Rev. 0.1 DS-CP20.241-R2-EN

All parameters are typical values specified at 20A, 230Vac, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.

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P R E L I M I N A R Y

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.

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. 25-4 Test circuit

Maximal wire length

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

MCB

Power Supply

AC

DC

+

-

Load

+

-

B-20A

1m

1m

2m

4m

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).