External Dc Supply - ABB ACS850 Application Manual

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
= 1/2 · (2400 µF + 4700 µF + 8600 µF) · (1.35 · 400V)
E
tot
The charging resistor of the ACS850-04-430A-5 (G) is able to withstand the whole
charging energy,
= 2289 J < E
E
tot
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
= ½ ·(2 ·4700 µF + 3 ·8600 µF)· (1.35 ·500V)
E
tot
exceeds the energy pulse withstand of the ACS850-04-430A-5 (G) charging circuit.
E
tot
Charging resistors of two ACS850-04-430A-5 (G) are able to withstand the charging
energy,
= 6971 J < E
E
tot

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
Example
Needed DC power is 250 kW, supply frequency 50 Hz and supply voltage is 400 V.
L = (0.03 × (400 V)
v
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
charging
Common DC configurations
= 5600 J.
r
= 2 · 5600 J.
r
2
= X × U ÷ 2πfP
v DC
2
) ÷ (2π × 50 Hz × 250 kW) = 61 µH.
capacity.
· 10–6 = 1866 J
2
·10–6 = 6971 J
2
Checking the