Safety information
Operating instructions SVCD(S)
17
123456278
-
419A58
Elektrotechnische Anlagen GmbH
1
Length of the DC-connection
The maximum inductivity of the DC-connection between output B6 Bridge of the in-
verter and the power feedback device mustn't exceed a certain level, as this inductivity
inducts an additional voltage to the DC-bus, when the IGBT’s are switched off. To
avoid an overload to the components of the power feedback unit, this additional voltage
must not exceed 100V. Resulting from this and other relevant characteristics of the
power feedback unit (DC-capacity and absolute maximum value of the grid current) the
maximum inductivity
(
)
2
2
max
ˆ
i
U
C
L
GL
∆
⋅
=
can be calculated.
The maximum valid line inductance for the feedback unit and the coupling inductance
between the two DC lines
(
)
25
,
0
ln
0
/
+
=
⋅
µ
−
+
r
a
l
L
π
follows at a by the ampacity specified
cross section of the conductor a maximum length of the connecting cable.
This inductivity always has to be higher or equal than the sum of the DC-bus inductivity
of the frequency inverter and the conductor inductivity of the DC connection.
The DC-bus inductivity of the frequency inverter has only to be considered, if it is
placed between the inverter B6 bridge and the power feed-back unit. The cables, which
are normally used for power applications, have an inductance per unit length of about
0,6µH/m.
If the values of the input capacitance C, the during power feed back maximum allowed
rise of the DC-voltage
∆
U
GL
=100V, the top level of the AC-current of the device (
i
ˆ
=2*I
eff
),, the inductance per unit length L´
(
)
25
,
0
ln
´
0
+
=
µ
r
a
L
π
and the inductance of the
DC-bus ´choke
L
ZKD
are known the maximum longitude of the conductors can be calcu-
lated with the following equation:
L
L
L
i
U
C
l
ZKD
GL
′
−
′
⋅
∆
⋅
=
2
2
max
ˆ
