Siemens SINAMICS G130 Engineering Manual page 216

Fundamental Principles and System Description
Engineering Information
The maximum permissible system pressure in the heat sink relative to atmosphere and therefore in the cooling circuit
must not exceed 600 kPa (6 bar). If a pump which can exceed this maximum pressure is used, appropriate measures
must be taken in the plant to limit the pressure to the maximum permissible value. A relatively low pressure drop
between the coolant in the inflow and return flow lines should be selected so that pumps with a flat characteristic
curve can be used. The minimum pressure difference (pressure drop) across a heat sink should equal 70 kPa
(0.7 bar) to ensure that the required coolant flow rate (l/min) specified in the technical tables of catalog D 21.3 is
achieved. The maximum permissible pressure drop across a heat sink is 200 kPa (2 bar) because the risk of
cavitation and abrasion increases significantly owing to the high flow rates with larger pressure drops.
When the cooling circuit is dimensioned, it is recommended that the pressure drop between inflow and return flow
should be selected such that it satisfies the following formula:
"dPi" in this formula denotes the pressure drops of the individual components in the cooling circuit (pipes, valves,
SINAMICS units, heat exchangers, dirt filters, inspection glass, etc.).
Pressure drop as a function of volumetric flow for water (H2O) mixed with anti-freezes as the coolant
If a mixture of water (H2O) and anti-freeze is used as the coolant instead of pure water (H2O), both the kinematic
viscosity and the thermal capacity of the coolant change. The required pressure drops therefore needs to be adjusted
depending on the mixture ratio in order to ensure an adequate flow rate dV/dt through the units.
Depending on the mixture ratio of water (H2O) and anti-freeze (Antifrogen N, Varidos FSK or Antifrogen L) and the
coolant temperature, the pressure drops across the heat sinks vary as a function of the coolant flow rate dV/dt, as
illustrated in the diagrams below.
Coolant mixture comprising water and anti-freeze Antifrogen N or Varidos FSK
The following diagrams specify the pressure drop across the heat sink as a function of the volumetric flow rate dV/dt
for different liquid-cooled SINAMICS S120 units when Antifrogen N or Varidos FSK anti-freeze is used.
Varidos FSK has the same flow properties as Antifrogen N.
Pressure drop as a function of volumetric flow rate for Basic Line Modules in frame size FBL
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