Cooling Circuit Configuring Information - Siemens SINAMICS S120 Equipment Manual

Cooling circuit, coolant properties and protection against condensation
9.1 Cooling circuits
9.1.3

Cooling circuit configuring information

The operating pressure must be set according to the flow conditions in the supply and return
lines of the cooling circuit. The required coolant flow rate per time unit must be set according
to the technical data of the relevant devices. The devices are normalized to a rated pressure
of 70 kPa (for water as coolant).
If a mixture of antifreeze and water is used as a coolant, the rated pressure must be
calculated according to the ratio.
The maximum permissible pressure to atmosphere in the heat sink and thus in the cooling
circuit must not exceed 6 bar. If the pump used can reach a maximum pressure in excess of
this value, appropriate measures (safety valve p ≤ 6 bar, pressure control or similar) must be
implemented by the customer to ensure that the maximum pressure limit is not exceeded.
The lowest possible differential pressure between the coolant in the supply and return lines
should be selected to allow use of pumps with a flat characteristic.
The maximum differential pressure across a heat sink is 150 kPa (for water as coolant);
higher differential pressures significantly increase the risk of cavitation and abrasion.
Figure 9-3 Pressure drop as a function of volumetric flow
Water cooling systems with series-connected SINAMICS devices should be avoided for the
following reasons:
● The risk of cavitation and abrasion increases as a result of the high total volumetric flow.
The material-dependent maximum velocity is exceeded.
● It is not possible to connect SINAMICS S120 in series because the total volumetric flow
inherent to any series connection requires system pressures in the 600 kPa range or
above.
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Water-cooled chassis power units for common cooling circuits
Manual, 08/2017, 6SL3097-4AM10-0BP0