Nord Drivesystems NORDAC LINK SK250E-FDS - Reduced Output Power; Increased Heat Dissipation Due to Pulse Frequency; Figure 6: Heat Losses Due to Pulse Frequency

8 Additional information
BU 0250 en-3021 189
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8.4 Reduced output power
The frequency inverters are designed for special overload situations. For example, 1.5x overcurrent
can be used for 60 s. For approx. 3.5 s, 2x overcurrent is possible. A reduction of the overload
capacity or its duration must be considered for the following circumstances:
• Output frequencies < 4.5 Hz and DC voltage (stationary pointer)
• Pulse frequencies greater than the nominal pulse frequency (P504)
• Increased mains voltages > 400 V
• Increased heat sink temperature
The following characteristic curves can be used to obtain the corresponding current/power limit.
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8.4.1 Increased heat dissipation due to pulse frequency
This illustration shows how the output current must be reduced, depending on the pulse frequency for
230V and 400V devices, in order to avoid excessive heat dissipation in the frequency inverter.
For 400V devices, the reduction begins at a pulse frequency above 6kHz. For 230V devices, the
reduction begins at a pulse frequency above 8kHz.
The diagram shows the possible current load capacity for continuous operation.
1.2
0.4
k
400V
f
pul
s
k
230V
f
puls
163 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]
Figure 6: Heat losses due to pulse frequency
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