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3.6 Example Calculation for the Power Supply
The power supply must be calculated individually for each station installation. Therefore the
simultaneity factor g and the current demand of each module, as well as the devices to be
connected must be established (refer to the example calculation table).
In the example station, an EPXPNS001 network adapter is configured with four EP-1214 modules
and eight EP-2218 modules. The cumulative current demand for each module is now calculated to
determine whether and at which point a EP-7631 power-feed module must be positioned to refresh
the current path. A power-feed module must always be used where the current demand
exceeds 10 A.
Note: The power refresh must be separately calculated for the input and output current paths. The
system voltage need not be considered during this step.
Note: Use the RSTi-EP Power Supply Configuration Guide to perform this calculation automatically.
3.6.1 Calculation of the Current Demand for the Input Current
The current consumption of the network adapter must be considered for the main power supply,
and the sum of consumption values is multiplied by the simultaneity factor g for each following
module:
I
network adapter
SYS
+ (I
+ I
) + (I
x g) module 1
SYS
IN
S
+ (I
+ I
) + (I
x g) module 2
SYS
IN
S
+ Σ ((I
+ I
) + (I
x g)) modules 3 to
SYS
IN
S
4
= Cumulative current demand
In the case of an additional power supply (power refresh) with a EP-7631 power-feed module, only
the sensor power supplies and the module current consumption have to be considered:
((I
+ I
module x) x g)
IN
S
+ ((I
+ I
module y) x g)
IN
S
+ Σ ((I
+ I
) x g) n modules
IN
S
= Cumulative current demand
GFK-2958E
I
Current consumption from the system current path
SYS
I
Current consumption from the input current path
IN
I
Power supplies for the connected sensors
S
I
Current consumption from the system current path
SYS
I
Power supplies for the connected sensors
S
RSTi-EP User Manual
Chapter 3: Configuration
31
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