ABB ACS850 series, Application Manual

Page: 24 / 39

24
Example 1
The DC buses of three converters ACS850-04-103A-5 (E0), ACS850-04-0202A-5 (E)
and ACS850-04-430A-5 (G) are connected together. The main supply voltage is 400 V.
The total charging energy of the capacitors is
E
tot
= 1/2
·
(2400 µF + 4700 µF + 8600 µF)
·
(1.35
·
400V)
2
·
10–6 = 1866 J
The charging resistor of the ACS850-04-430A-5 (G) is able to withstand the whole
charging energy,
E
tot
= 2289 J <
E
r
= 5600 J.
Example 2
The DC buses of two ACS850-04-202A-5 (E) and three ACS850-04-430A-5 (G) are
connected together. The main supply voltage is 500 V. The total charging energy of the
DC link capacitors is
E
tot
= ½
·
(2
·
4700 µF + 3
·
8600 µF)
·
(1.35
·
500V)
2 ·
10–6 = 6971 J
E
tot
exceeds the energy pulse withstand of the ACS850-04-430A-5 (G) charging circuit.
Charging resistors of two ACS850-04-430A-5 (G) are able to withstand the charging
energy,
E
tot
= 6971 J <
E
r
= 2
·
5600 J.
External DC supply
The drive modules can also be supplied from an external DC supply. This can be the
case if:
•
the needed DC link power can not be handled with any available drive module. In
this case, some other diode supply unit can be used.
•
the regenerative power should be fed back to the AC supply. Then it is possible to
use ABB’s regenerative supply units (ISU).
6-pulse or higher pulse number diode supply or regenerative supply are suitable.
AC- or DC-choke is needed in external supply circuit to reduce drive units DC-link
capacitors ripple current to acceptable level.
Recommended choke relative reactance is 3%. Choke phase inductance is calculated
by formula L
v
=
X
×
U
2
÷ 2 π
fP
DC
Example
Needed DC power is 250 kW, supply frequency 50 Hz and supply voltage is 400 V.
L
v
= (0.03 × (400 V)
2
) ÷ (2 π × 50 Hz × 250 kW) = 61 µH.
The recommended charging resistor value is the same as the minimum or nominal
resistance of the highest power converter used given in the table in
Checking the
charging capacity .
Common DC configurations