Electrical installation
68
───
Version: 2.1
eXtended Transport System
Earthing of the supply
No fuses exist
The figure below is for illustration purposes only. No necessary
fuses exist or are pictured in the simplified illustration.
Power Supply
24 V
48V
GND
24V
EtherCAT
cable
Power Supply
48 V
Control cabinet earth
3
3
3
4
4
1
1
2
2
2
4
4
4
3
3
1
1
1
2
2
2
2
2
2
2
1
1
1
4
4
4
4
4
4
3
3
3
3
3
3
3
3
3
3
3
4
4
3
3
3
4
4
1
1
1
2
1
1
2
2
1
2
1
2
2
1
1
2
Control circuit
Chapter 9.4.3.1. (earth leakage) of the EN60204-1 standard stipu-
lates that 24 V
DC
control circuits must be earthed. The earthing pre-
vents the automatic start-up of a machine in the case of a cross-cir-
cuit.
U
U
R 24 V
R 48 V
I 48V
I 48V
I 24V
I 24V
I compensation = 0 A
U 48 V
U 24 V
0,75 mm
2
0,75 mm
2
2,5 mm
2
2,5 mm
2
Modules
Supply line 3 x 2,5 mm / 2 x 0,75 mm
2
2
2,5 mm
2
Power supplies
Load current circuit
Beckhoff recommends that you don't earth the 48 V power
supply unit
The 24 V
DC
return line (0.75 mm
2
) could be overloaded.
If the 48 V power supply unit is earthed, the currents will be distrib-
uted to the 48 V
DC
and 24 V
DC
return lines in accordance with the im-
pedances. Equalizing currents will then flow via the earth on the
power supply unit, as a result of which the 24 V
DC
return line
(0.75 mm
2
) could be overloaded.
U
U
R 24 V
R 48 V
(I 24 V + I 48 V) / 2
I 48 V
(I 24 V + I 48 V) / 2
I 24 V
I compensation =
(I 24 V + I 48 V) / 2
U 48 V
U 24 V
0,75 mm
2
0,75 mm
2
2,5 mm
2
2,5 mm
2
2,5 mm
2
Modules
Supply line 3 x 2,5 mm / 2 x 0,75 mm
Power supplies
I compensation =
(I 24 V + I 48 V) / 2
2
2
