Fundamental Principles and System Description
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
161/528
Permissible output current in operation without overload with occasional
periods of low output frequencies as a function of the output frequency
1.12.3.1.2 Operation without overload with frequent periods of low output frequencies < 10 Hz
In this case, the converter must be configured to ensure that the thermal monitoring model does not trigger
inappropriate overload reactions and that the lifetime of the IGBTs is not significantly reduced.
If the converter is to be operated frequently, i.e. for a period corresponding to more than approximately 1 % to max.
2 % of its total operating period, or continuously at output frequencies of less than 10 Hz without intervention of an
overload reaction and without risk of premature IGBT failure, the output current must be reduced as a function of the
output frequency according to the derating curve below.
Permissible output current in operation without overload with frequent periods
of low output frequencies as a function of the output frequency
1.12.3.2 Operation with high overload at low output frequencies < 10 Hz
As the output frequency decreases, the absolute chip temperature T
Chip
reaches its limit value after ever shorter
periods of overload with the result that the thermal monitoring model might eventually intervene after very short
periods of overload. This must be taken into account at the configuring stage.
As the output frequency decreases, the temperature swing ΔT
Chip
also increases continuously during the overload
period. If the periods of overload occur frequently or periodically with more than approximately 1 % to max. 2 % of the
total operating period, measures must be taken to ensure that the lifetime of the IGBTs is not reduced.
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