Eaton Rapid Link 5 - Page 52

2 Engineering
2.6 Power bus
48 Rapid Link 5 · RAMO5 · RASP5 05/20 MN034004EN www.eaton.com
Calculate the short-circuit current and the voltage drop as specified in
DIN VDE 0100 to make sure that the protection requirements are being met.
The power bus' cable length can be calculated as follows:
Figure 18: Example: RAMO5
Requirements for the group protection device during short-circuits.
The short-circuit current I
k
must be greater than the tripping current of the
short-circuit trip actuator I
rm
. It depends on the impedance or length of the
energy bus and the stub line.
Depending on the power bus’ length and the configuration of the power
branches, the total of all RAMO5 and RASP5 supply system currents during
continuous operation must not exceed 25 A (4-mm
2
power bus).
l =
U
0
x 1000
– Z
v
– (Z
stub
xl
stub
)
I
rm
Z
power bus
l = Cable length (maximum: 100 m)
U
0
= 230 V (single-phase no-load voltage)
I
rm
= Tripping current of short-circuit release
z
v
= External supply impedance (e.g., 100 mΩ)
Z
Stub
= 35.50 mΩ/m (stub line 1.5 mm
2
)
Z
power bus
= 13.40 mΩ/m (power bus 4.0 mm
2
)
21.50 mΩ/m (power bus 2.5 mm
2
)
￫
Take the voltage drop under load into account when selecting
the cable cross-section.
The user is responsible for taking other applicable standards
(e.g., VDE 0113, VDE 0289) into account.
3 AC 400 V∼, 50/60 Hz
I
rm
I
k
Q1
l
M
3 ∼
RAMO
1.5 mm
2
4 mm
2
I >
l
Stich
1.5 m
(4.92 ft)
1.5 m
(4.92 ft)