Thermal Monitoring Of The Power Unit During Load Duty Cycles And Continuous Operation - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information

Thermal monitoring of the power unit during load duty cycles and continuous operation

In both load duty cycle mode and continuous operation, the power unit of the SINAMICS G130, G150, S150
converters and S120 Motor Modules (Chassis and Cabinet Modules) is thermally monitored by three different
methods:
•
The output current is monitored by an I
•
The heatsink temperature is monitored by direct temperature measurements.
•
The chip temperature of the IGBTs is monitored by the thermal model which can calculate the exact
temperature of the IGBT chips on the basis of the heatsink temperature measurement plus other electrical
quantities such as pulse frequency, DC link voltage and output current.
If a power unit overload is detected by these monitoring functions, an overload reaction defined by the setting in
parameter P0290 is triggered. The following overload reactions can be parameterized:
•
Reduce output current in vector control mode or output frequency in V/f mode.
•
No reduction, but shutdown (trip) when the overload threshold is reached.
•
Reduce the output current or output frequency and pulse frequency (not by I
•
Reduce the pulse frequency (not by I
With many applications, the parameterizable overload reaction makes it possible to prevent instantaneous shutdown
when the power unit is overloaded briefly. For example, it is perfectly tolerable with most pump and fan applications
for the flow rate to drop briefly when the output current is reduced. If the drive is operating on a higher pulse
frequency than the factory setting in order to achieve a reduction in motor noise, for example, a possible overload
reaction would be to reduce the pulse frequency and thus maintain the flow rate.
If the parameterized overload reaction cannot reduce the overload sufficiently, then the drive will always shut down in
order to protect the power unit. This means that the risk of irreparable damage to the power unit as a result of
excessive IGBT temperatures is absolutely eliminated in all operating modes.
These protection mechanisms implemented in the SINAMICS units do, however, demand precise configuring of the
converter in relation to its load profile so that the drive can perform all the required functions without interruption by
overload reactions.
SINAMICS Engineering Manual – May 2008
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© Siemens AG
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