How do I dimension the power
supply of my SmartWire-DT
topology?
39
02/11 MN05006002Z-EN
Figure 5:
Power supply in the SmartWire-DT network
a
Supply unit: SmartWire-DT gateway or SmartWire-DT power
feeder module
The following is valid in accordance with figure 5:
X
First determine the total current by adding the current
consumption of all SmartWire-DT slaves as listed in the
tables in the appendix of manual MN05006001Z-EN,
“SmartWire-DT Slaves”, including the current consump-
tion of the network connection (17 mA).
X
Refer to the illustration „Line resistance of SmartWire-DT
ribbon and round cable in the device and contactor
supplies“, page 37 or the table „Line resistance of the
SmartWire-DT ribbon cable and round cable“ page 36 for
the total line resistance subject to consideration of the
length of the various SmartWire-DT line types.
I
G
I
n
I
RB
U
L1
U
V
U
1
U
2
U
3
U
n
U
L2
U
L
3
U
Ln
R
L1
R
L2
R
L
3
R
Ln
R
B
SWD
(1)
SWD
(2)
SWD
(
3
)
SWD
(n)
a
L1
U
V
= U
VP
= 14.5 V DC
U
1
= U
V
- R
L1
x (I
1
+ I
2
+ I
3
+ … + I
n
+ I
RB
)
U
2
= U
1
- R
L2
x (I
2
+ I
3
+ … + I
n
+ I
RB
)
U
n
= U
n-1
- R
Ln
x (I
n
+ I
RB
)
h
Caution!
In the case of this simplified formula the current limitation
due to the cable resistance remains unconsidered and the
rated operational current of the individual SmartWire-DT
slaves is assumed at all times. The result is valid at a
supply voltage U
n
f
of 10.5 V DC.
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