Burkert Type 8644 - Manual (Page 32)

28 - 8644/phoenix
S
YSTEM
D
ESCRIPTION
POWER LOSS
Formula for calculation of the power loss of the electronics
P
EL
= P
Bus
+ P
Peri
Substituting the maximum currents of 2 A (logic) and 0.5 A (for analog terminals) in the formula for
calculation of the power loss with periphery connected, we obtain:
P
PERI
= 2.2 W + 0.35 W = 2.55 W
This 2.55 W corresponds to 100 % network loading capacity in the derating curves.
Derating
ATTENTION!
Make sure that at an ambient temperature above 40 °C, the nominal loading capacity
given by the derating curves is not exceeded. As can be seen from the formula, the total
loading with attached periphery (P
PERI
) is the relevant quantity. If for example no current is
consumed by the analog supply, the fraction of the current from the logic supply may be
greater.
Where
P
EL
Total power loss in the terminal
P
BUS
Power loss for bus operation without peripheral loading (constant)
P
PERI
Power loss with periphery connected
I
LN
Current consumption of participant n from logic supply
n Index designating the number of participants connected (n = 1 to a)
a Number of participants connected (supply with logic voltage)
Σ
I
Ln
Sum of all current consumed by participants from the 7.5 V logic supply (max. 2 A)
I
LM
Current consumption of participant m from analog supply
m Index designating the number of nalog participants connected (m = 1 to b)
b Number of analog participants connected (supply with analog voltage)
Σ
I
Lm
Sum of all current consumed by participants from the 24 V analog supply (max. 0.5 A)
a
n=0
b
m=0
W
A
W
A
P
EL
= 2,6 W + (1,1 x
Σ Σ Σ Σ Σ ΙΙΙΙΙ
Ln
) + (0,7 x
Σ Σ Σ Σ Σ ΙΙΙΙΙ
Lm
)
a b
n=0 m=0