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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
÷ 2πfP
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
) ÷ (2π × 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
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