User manual

4 Conguration | Calculation of power loss
27Manual u-remote1432790000/08/12.2015
4.7 Calculation of power loss
The power loss of the eldbus coupler is calculated als fol-
lows:
P
coupler
= P
0
+ N
*
P
mod
+ I
in
*
ΔU
in
+ I
out
*
ΔU
out
P
0
Static power loss in the eldbus coupler 24V
*
I
SYS
I
SYS
Current consumption from the system current
path
See table "Cur-
rent demand" in
section4.5
N Number of modules
P
mod
Power loss due to module supply from the
system current path
0.02 W
I
in
Current fed in through the input current path
ΔU
in
Voltage drop across the contacts in the input
current path
0.18 V
I
out
Current fed in through the output current path
ΔU
out
Voltage drop across the contacts in the output
current path
0.18 V
The power loss of a u-remote station is calculated using the
power loss of the eldbus coupler and the power loss of the
individual modules. It depends on the current in both current
paths. It is assumed that there is a maximum power loss
(
P
module
) of 2watts for the modules.
P
station
= P
koppler
+ N
*
P
module
Maximum values were assumed for these calculations. If you
need detailed calculations, please contact the Weidmüller
Service.
4.8 Feedback energy in DO modules
With digital output modules, power is fed back through the
channels when inductive loads are switched off. The respec-
tive permissible breaking energy is noted in the technical
data of the DO modules. Depending on the switching fre-
quency the breaking energy leads to additional energy loss
in the output module.
If the maximum permissible output power loss of a module
is exceeded, the module shuts down temporarily.
Feedback energy can be prevented by install-
ing external freewheeling protection. With it,
the same switching rate can be achieved with
an inductive load as with a resistive load.
Calculation of output power loss
The module specic data needed to calculate the output
power loss are provided in the ATEX certicate which you
can download from the Weidmüller website.