Required Partitioning - Siemens SINAMICS G130 Engineering Manual

General Engineering Information for SINAMICS
Engineering Information
3.6.5

Required partitioning

Partitions must be installed in the cabinet in order to prevent "air short circuits" or undesirable air circulations inside
the cabinet. This effect can impair the cooling of components mounted in the cabinet, cause them to overheat and
shut down the drive.
The fans integrated in the air-cooled SINAMICS S120 Chassis units and in the air-cooled SINAMICS G130 Chassis
units produce a vertical upward air flow, thereby creating underpressure at the bottom of the cabinet and
overpressure at the top. The underpressure conditions at the bottom of the cabinet cause cold air from outside the
cabinet to be sucked in through the air openings at the bottom. This cold air flows upwards through the Chassis,
heating up as it moves. The overpressure conditions at the top of the cabinet cause the heated air to be blown out of
the cabinet through the air openings at the top.
Cooling conditions can be described as optimal whenever all the cold inlet air sucked in at the bottom of the cabinet
exits as heated outlet air after it has flown through the Chassis.
These conditions can be achieved only
through the placement of partitions in the
cabinet. The purpose of these partitions is to
prevent air short circuits in the cabinet, i.e. to
hinder the heated air at the top from flowing
back down inside the cabinet. The diagram on
the right illustrates the air flow conditions in
the cabinet when suitable horizontal and
vertical partitions are used.
Without partitioning, the internal pressure
conditions could cause a major part of the
heated air to flow inside the cabinet from the
top along the sides and the front of the
Chassis down to the bottom. The result would
be that the Chassis would suck in heated air
as cooling air. As a consequence the cooling
conditions would deteriorate significantly,
causing the internal components to overheat.
Appropriately shaped sheet-metal or plastic
components can be used as partitions. The
partition must make close contact around all
four sides of the Chassis and with the side
panels and the door of the cabinet. It must
also be designes in such a way that the air
flow exiting the cabinet at the top is not
pushed into the cross-beams, but is guided
around it.
Guidance of cooling air in the cabinet / required partitioning
It is absolutely essential to provide partitioning in cabinets with degree of protection IP20 and even more in cabinets
with higher degrees of protection. This is because the wire lattices or filter mats used in highly protected cabinets
increase the flow resistance through the cabinet openings in proportion to the degree of protection and the risk of
internal air short circuits rises accordingly.
a number of Chassis units of the same frame size is installed in a single cabinet, each producing approximately
If
similar flow conditions (as illustrated in the diagram above), it is generally sufficient to install horizontal partitions in
the cabinet so as to prevent the flow of air from the top to the bottom inside the cabinet.
In contrast, if several Chassis units of widely differing frame sizes producing very dissimilar flow conditions are
mounted in the same cabinet, the individual units must be separated not simply by horizontal partitions, but by
vertical partitions as well. There is otherwise a risk that Chassis units of smaller frame sizes and correspondingly low
fan capacity will no longer be able to generate a satisfactory cooling air flow. This is because the overpressure
created at the top of the cabinet by the Chassis units with bigger frame sizes will increase too far.
SINAMICS Engineering Manual – November 2015
269/528
Ó Siemens AG