Safety information
18 Operating instructions RHD
ELTROPLAN
-
REVCON
Elektrotechnische Anlagen GmbH
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 maxi-
mum inductivity can be calculated.
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 feedback maximum
allowed rise of the DC-voltage
∆
U
GL
=100V, the top level of the AC-current of the de-
vice
the inductance per unit length L´
and the inductance of the DC-bus ´choke
L
ZKD
are known the maximum longitude of the
conductors can be calculated with the following equation:
L
L
L
i
U
C
l
ZKD
GL
′
−
′
⋅
∆
⋅
=
2
2
max
ˆ
eff
I
i
×
=
2
ˆ
2
(
)
2
2
max
ˆ
i
U
C
L
GL
∆
⋅
=
eff
I
i
×
=
2
ˆ
2
(
)
25
,
0
ln
´
0
+
=
⋅
µ
r
a
l
L
π
