NORDAC SK 5xxE Manual
152
Subject to technical alterations
BU 0500 GB
8.5.3 Reduced overcurrent due to output frequency
To protect the power unit at low output frequencies (<4.5Hz) a monitoring system is provided, with which the
temperature of the IGBTs (
integrated gate bipolar transistor)
due to high current is determined. In order to
prevent current being taken off above the limit shown in the diagram, a pulse switch-off (P537) with a variable
limit is introduced. At a standstill, with 6kHz pulse frequency, current above 1.1x the nominal current cannot be
taken off.
x f
( )
In_60sec f
( )
In_1sec f
( )
f
0
2
4
6
8
10
12
14
16
18
20
0
0.5
1
1.5
2
2.5
I / I
N
Output frequency [Hz]
Prohibited region
The upper limiting values for the various pulse frequencies can be obtained from the following tables. In all
cases, the value (0.1…1.9) which can be set in parameter P537, is limited to the value stated in the tables
according to the pulse frequency. Values below the limit can be set as required.
230V devices:
Reduced overload capacity (approx.) due to pulse frequency (P504) and output frequency
Output frequency [Hz]
Pulse frequency [kHz]
4.5
3.0
2.0
1.5
1.0
0.5
0
3...8
200% 170% 150% 140% 130% 120% 110%
10
180% 153% 135% 126% 117% 108% 100%
12
160% 136% 120% 112% 104% 96% 95%
14
150% 127% 112% 105% 97% 90% 90%
16
140%
119%
105% 98% 91% 84% 85%
400V devices:
Reduced overload capacity (approx.) due to pulse frequency (P504) and output frequency
Output frequency [Hz]
Pulse frequency [kHz]
4.5
3.0
2.0
1.5
1.0
0.5
0
3...6
200% 170% 150% 140% 130% 120% 110%
8
165% 140% 123% 115% 107% 99% 90%
10
150% 127% 112% 105% 97% 90% 82%
12
130%
110% 97% 91% 84% 78% 71%
14
115% 97% 86% 80% 74% 69% 63%
16
100% 85% 75% 70% 65% 60% 55%
