The service life of drive converters with voltage DC link depends on the current load
of the electrolytic capacitors in the DC link. The use of mains chokes can increase the
service life of the condensators to a considerable extent, especially when connecting to
„hard“ power systems or when under permanent drive load (continuous duty). For con-
tinuous duty (S1) drives with a medium duty of > 60%, KEB provided the use of mains
chokes with a terminal voltage (Uk) of 4%.
The term "hard" power system means that the nodal point power (
S
Net
) of the mains is
very high (>> 200) compared to the output rated power of the drive converter (
S
A
).
k =
S
Net
>> 200
e.g.
k =
2 MVA (Supply transformer)
= 303 ––> Choke required
––––
–––––––––––––––––––––
S
out
6.6 kVA (12G6)
3.4 Overload and Derating
80
100
120
140
160
180
200
220
fd
(6 Hz)
f0
(0 Hz)
f
out /
Hz
I
N
/ %
HSR
I
N
OC
I
max
09G6 / 8 kHz
10G6 / 8 kHz
07G6 (8 kHz) & 09/10G6 (4 kHz) =
Imax
Figure 1:
Maximum load and derating depending on the switching frequency
29
OVerLOAD AND DerATING
