NORD Drivesystems BU0180 - Manual (Page 165)

9 Additional Information
BU 0180 GB-0914 Pre-series version 165
9.4 Reduced output power
The frequency inverter is designed for certain overload situations. For example, 1.5x overcurrent can be
used for 60 sec. For approx. 3.5 sec a 2x overcurrent is possible. A reduction of the overload capacity or its
time must be taken into account in the following circumstances:
o Output frequencies < 2Hz and constant voltages (needle stationary)
o Pulse frequencies greater than the default pulse frequency (P504)
o Increased mains voltage > 400 V
o Increased heat sink temperature
On the basis of the following characteristic curves, the particular current / power limitation can be read off.
9.4.1 Increased heat dissipation due to pulse frequency
This illustration shows how the output current must be reduced, depending on the pulse frequency for 230 V
and 400 V devices, in order to avoid excessive heat dissipation in the frequency inverter.
For 400 V devices, the reduction begins at a pulse frequency above 6 kHz. For 230 V devices, the reduction
begins at a pulse frequency above 8 kHz.
Even with increased pulse frequencies the frequency inverter is capable of supplying its maximum peak
current, however only for a reduced period of time. The diagram shows the possible current load capacity
for continuous operation.
1.2
0.4
k 400V f puls
k 230V f puls
16 3 f puls
4 6 8 10 12 14 16
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
I / I
N
Pulse frequency [kHz]