Installation and Commissioning
18
sysmik.de
Manual SCA-340 / SCA-340-L
3.2.2.3
Current Consumption Calculation for a Scalibur Station (with Terminals)
To find a suitable external power supply, the current consumption of the entire
Scalibur station has to be considered:
I
IS
= I
SCA
+ I
USB
+ I
K
+ I
AS
I
IS
current consumption of the entire Scalibur Inline station
I
SCA
current consumption of the Scalibur
I
USB
current consumption of connected USB devices
I
K
current consumption of connected terminals
I
AS
current consumption of sensors and actuators, fed by the Inline station
The current consumption of a Scalibur (without terminals) is maximum 170 mA.
I
SCA
= 0.17 A
Please consult the manual of the connected USB device to find out the actual
current draw from USB.
The respective USB currents IUSB1 and IUSB2 are weighted by a factor of 0.24,
resulting in the equation:
I
USB
= (I
USB1
+ I
USB2
) × 0.24
The current consumption of the connected terminals can be found in their manuals.
The following rules of thumb apply:
The current provided by U
ANA
influences the total current directly.
The current provided by U
L
applies to the total current with a factor of 0.36.
The following formula applies:
I
K
= I
A
+ I
L
× 0.36
I
A
current from U
ANA
(max. 500 mA)
I
L
current from U
L
(max. 2.0 A)
See the according datasheets in order to determine the current consumption of the
connected actuators and sensors.
For an estimation it is often sufficient to check, whether the supply can be provided
completely by the Scalibur, that is without power or boost terminals.
Without power and boost terminals and regardless of the circuits U
M
und U
S
, the
maximum current consumption of the Scalibur with connected terminals is 1.7 A.
In addition there are the current requirements of the sensors and actuators, whereas
the current through feather keys and keyways is limited to a maximum of 8 A.
Note:
When selecting an external power supply, plan sufficient reserves. also into account
that it could come to a current increase to a multiple of the rated current in the moment of
turn-on caused by input capacities. Power supplies with over current shut-down must have a
sufficient response delay to avoid start-up problems.
3.2.2.4
Derating of Terminal and USB Supply
Because USB and the Inline terminals are supplied by Scalibur’s internal power
supply unit, an increased load there increases Scalibur’s internal power dissipation.,
Therefore, a derating has to be observed, which is depending on the mounting
position (see Fig. 3.2.2.4). The recommended mounting position (with least derating)
is horizontally (that is, clipped to a horizontal DIN rail on the wall).
The internal power dissipation caused by USB loads (P
USB
) and the connected Inline
terminals (P
PERI
) is calculated according to chapter 0.