Burkert Type 8644 - Manual (Page 34)

30 - 8644/phoenix
S
YSTEM
D
ESCRIPTION
Example:
Current loading of periphery supply: 8A
Ambient temperature: 55 °C
1. Nominal loading capacity of the logic and analog supply: 50 % (from graph)
I
LLogik
= 1 A, I
LAnalog
= 0.25 A
P
PERI
= 1.1 W + 0.175 W
P
PERI
= 1.275 W (equals 50 % of 2.55 W)
2. Possible logic current when analog supply is not loaded:
P
PERI
= 1.1 W/A x I
LLogik
+ 0 W
P
PERI
/ 1.1 W/A = I
LLogik
I
LLogik
= 1.275 W / 1.1 W/A
I
LLogik
= 1.159 A
Common potentials
Main and segment supply lie electrically at the same potential. Their common mass is led from the bus
terminal via the potential shunter as reference mass GND to the participants.
Analog supply and 7.5 V logic supply are generated from the main supply. Their common mass LGND lies
electrically at the same potential as GND and is led from the bus terminal via the potential shunter as
reference mass LGND to the participants.
Protective features
Overvoltage Protective diodes at input (destroyed on continuous
(segment supply /main supply) overloading)
Loading peaks up to 1500 W are short-circuited by the input
diode.
False polarity Parallel polarity protection diodes; in case of error, the
(segment supply /main supply) high current through the diodes causes the upstream fuse
toblow.