Example Of A Closed Cooling Circuit For Liquid-Cooled Sinamics S120 Units; Example Of An Open Cooling Circuit For Liquid-Cooled Sinamics S120 Units - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information
1.16.4

Example of a closed cooling circuit for liquid-cooled SINAMICS S120 units

The following diagram shows a typical example of a closed cooling circuit. This cooling circuit is absolutely essential
for units with aluminum heat sink, through which the coolant directly flows. It is also highly recommended for units
with a heatsink with integrated stainless steel heat exchanger. In the diagram all important cooling circuit components
are shown.
The pressurizer, which must have a closed design, ensures an approximately constant pressure in the cooling
system even when there are large variations in the coolant temperature. It must always be installed directly on the
suction side of the pump, at which a minimum pressure of 30 kPa (0.3 bar) is required. The pump circulates the
coolant, whose flow area should be made of stainless steel. The maximum system pressure of the cooling circuit to
atmosphere must not exceed 600 kPa (6 bar). A pressure-relief valve must be installed for this purpose. The system
pressure is displayed on the pressure indicator. The pressure difference at the SINAMICS units produced by the
pump between the inflow and return flow must, on the one hand, be large enough to ensure the coolant flow rate
(coolant requirement) required for the cooling of the SINAMICS units as specified in Catalog D 21.3. On the other
hand, the pressure difference should not be unnecessarily high so as to avoid a significantly increased risk of wear as
a result of cavitation and abrasion caused by excessively high flow rates. Since the units are dimensioned such that
the volumetric flow rate (coolant requirement) stated in Catalog D 21.3 is reached with pure water as coolant at a
pressure difference of 70 kPa (0.7 bar), the pressure difference at the units should be dimensioned for between
around 100 kPa (1.0 bar) and maximum 200 kPa (2.0 bar) in order to ensure a particular volumetric flow rate margin
and also to keep the potential wear within acceptable limits.
Liquid-cooled SINAMICS S120 units in Chassis format: Recommendation for a closed cooling circuit
The connecting pipes between the individual components of the cooling circuit should be made of stainless steel or
ABS plastics. The seals must be chloride, graphite and carbon-free. To relieve the mechanical load on the SINAMICS
units, they must be connected by means of short insulating EPDM hoses with an electrical resistance of > 10
the pipework of the cooling system. Ideally, the heat exchanger as well as the piping, should be made of stainless
steel. However, if absolutely necessary, copper heat exchangers may be used, as long as the cooling circuit is of
closed type and the correct concentration of inhibitors or anti-freeze is used. Dirt traps retain dissolved solides
> 0.1 mm in size and prevent clogging of the heat sinks in SINAMICS units. The inspection glass is recommended for
diagnosing clouding or discolouration of the coolant, which indicates that corrosion and wear may have been
occured. . The bypass valve is required for the purpose of temperature control (condensation prevention).
1.16.5

Example of an open cooling circuit for liquid-cooled SINAMICS S120 units

The following diagram shows a typical example of an open cooling circuit. This type of cooling circuit must not be
used with units with aluminum heat sinks, through which the coolant directly flows, due to high oxygen levels. It can,
therefore, only be used with units with integrated stainless steel heat exchangers.
SINAMICS Engineering Manual – November 2015
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