Installation and Commissioning
Manual SCA-340 / SCA-340-L sysmik.de 19
Fig. 3.2.2.3: Derating diagram of maximum internal power dissipation
Please refer to the manuals of the Inline terminals to find out the load of the logic
supply.
Maximum load on the logic supply (2 A) and on USB (2 x 500 mA) leads to a 100%
power dissipation of 2.7 W:
P
V
= 1.0 V × I
L
+ 0.7 V × I
USB
P
V
= 1.0 V × 2.0 A + 0.7 V × 1.0
A = 2.7 W
This power dissipation can be maintained up to a maximum environmental
temperature of 40 °C (104 °F). For higher temperatures, the load (P
PERI
and P
USB
)
must be reduced according to Fig. 3.2.2.3.
Example 1: Horizontal mounting position
For an environmental temperature of 55 °C (131 °F) and horizontal mounting, the
power dissipation is limited to 87 %, which means 2.35 W. Supposed I
L
is fully
loaded with the max. allowed 2 A, then the USB ports can support a maximum of
0,5 A:
I
USB
=
0.87 P
V
– 1 V
×
I
L
0.7 V
I
USB
=
2.35 W – 2 W
0.7 V
= 0.5 A
0
20
40
60
80
100
-25 -15 -5 5 15 25 35 45 55
P
v
[%]
T
env
[°C]
horizontal mounting
other mounting positions
T
env
[°C] environmental temperature in °C
P
v
[%] Power dissipation of internal Scalibur supply in %
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