ABB ACS850 - Common DC Capacitance; DC Link Capacitance; Energy Capacity in Common DC

28
Common DC capacitance
Many acceleration and deceleration processes are typical for applications with high
performance machinery drives. It is useful for such applications to connect those drives
into the common DC link to utilize also the DC link energy storage behavior. In the
common DC system, all the capacitor banks of the individual drive modules are
connected in parallel and they act as a common energy storage. This provides the
following advantages:
• The need for the braking resistor in the drive system may be eliminated. The heat
dissipation in the control cabinet is considerably reduced.
• The energy stored in the DC bus capacitors during the regenerating can be used
afterwards for the motoring power. The energy demand from the supply is then
reduced.
DC link capacitance
Each drive module has its own capacitor bank. The capacitance value of each drive
size is given in the table below.
C
dc
C
dc
ACS850 Type
µF
ACS850 Type
µF
03A0-5, 03A6-5 120 103A-5 2400
04A8-5, 06A0-5, 240 144A-5 3600
010A-5 370 166A-5, 202A-5 4700
014A-5, 018A-5 740 225A-5, 260A-5, 290A-5 7050
025A-5, 030A-5, 670 430A-5 8600
044A-5, 050A-5 1000 521A-5 10800
061A-5 1340 602A-5 12900
078A-5, 094A-5 2000 693A-5, 720A-5 15100
Energy capacity in common DC
The energy capacity W
dc
in the common DC system can be determined in following
way:
()
(
)
22
321
2
dclim,dc
dcndcdcdc
DC
UU
C...CCC
W −×
+
+++
=
Where:
• C
dc1
…C
dcn
are the actual capacitance values of the drive modules connected to the
common DC link.
• U
dc,lim
is the DC link voltage level that is allowed for the system.
• U
dc
is the actual DC link voltage level in a normal situation.
The actual DC link voltage to be used in energy calculations should be calculated as:
•
acdc
UU ×= 2
Common DC configurations