Design; Power Limit - ABB ACS800 Application Manual

Design

Power limit

Total output power limit of the common DC system can be calculated with
equation 1.
P
out.tot
P
out.tot
and P
Only converters, which are connected to the main supply, are used for the power
limit calculations.
The power correction factor, k, for each combination can be found from Table 1.
When several converters are connected to the main supply, the least efficient power
correction factor is chosen from table 1, i.e. the smallest factor. See
Example2.
Table 1 Power correction factors
R2-R3
R4
R5-R6
R7-R8
Explanations of Table 1:
NO: The supply of the smaller converter MUST NOT be connected, because the
converters have different input chokes. Frame sizes R2...R3 have DC chokes and
frame sizes R4...R8 AC chokes.
C: If both converters are connected to the main supply, the DC links MUST be
connected together via contactor because the converters have different charging
circuits. In R2...R4 the charging resistors are in series with the DC capacitors and in
R5...R8 the charging resistor is in parallel with the input bridge. The DC contactors
are switched on after all of the DC links are charged and the converters are in the
READY state.
Note: The P
main supply.
⋅
= P + k P
1cont.max
is the instantaneous power limit of the installation. P
the highest drive power rating of the converters.
n.cont.max
R2-R3
k=0.5
NO
NO
NO
value is higher if the smallest converter is not connected to the
out.tot
⋅
+ k P
2cont.max n.cont.max
ACS800
R4
NO
k=0.7
k=0.7 C
k=0.7 C
(equation 1)
is the lowest
1cont.max
Example1
R5-R6 R7-R8
NO NO
k=0.7 C k=0.7 C
k=0.7 k=0.6
k=0.6 k=0.7
11
and
Design