Appendix A Charging Circuit Capacity; Frame Sizes R; Frame Sizes R5 - ABB ACS800 Application Manual

Appendix A Charging circuit capacity

The total power of the common DC system P
is not connected directly to the main supply. To determine whether it is possible to
leave some converters unconnected, the total charging energy of the DC capacitors
and associated inrush currents must be analysed.
Frame sizes R...R4
In frame sizes R2...R4 the charging resistor is in series with the DC capacitors and
all DC buses are charged via their own resistors despite of the main supply
connection. The inrush current remains at an acceptable level, if the maximum
number of unconnected converters per one connected converter is five.
Note: Always connect the biggest converter to the main supply.
Frame sizes R5...R8
In frame sizes R5...R8 the charging circuit is in parallel with the input bridge. The
charging resistor of the connected converter limits the number of the unconnected
converters. The charging circuit of the connected converter must be able to
withstand the total charging energy E
E
rconnected
E
rconnected
The charging energy of the DC link capacitors of a single converter can be
calculated with equation 8.
E =
C
DC
U
net
The total charging energy of the system E
of single converters.
E
tot
>
E
tot
= charging resistor's energy pulse withstand of the connected
converter
1
⋅ ⋅ ( ⋅
-- - C
1.35 U
DC net
2
= capacitance of the DC-bus capacitor. See
= actual supply voltage
1
⋅ ( ...
-- -
= C + + C
DC1
2
out.tot
, i.e.
tot
2
)
is calculated by summing the energies
tot
2
) ⋅ ( ⋅ )
1.35 U
DCn net
is higher if the smallest converter
Table 3.
Appendix A Charging circuit capacity
25
equation 7
equation 8
equation 9