Requirements Concerning Coolant And Cooling Circuit - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information

Requirements concerning coolant and cooling circuit

The coolant required for SINAMICS S120 Liquid-Cooled units is either water or a mixture of water and anti-freeze. In
the cooling circuit, electro-chemical processes can occur, which lead to corrosion. The occurrence of these
processes depends on several factors:
•
The type of cooling circuit (open or closed cooling system)
•
The materials used in the cooling circuit (metals, plastics, rubber seals and tubes)
•
The electro-chemical potentials in the cooling circuit
•
The chemical composition of the coolant and other additives (inhibitors, anti-freeze, biozides)
In order to prevent these corrosive, electro-chemical processes, or at least to keep them to a minimum, which will
allow problem-free operation of the cooling circuit for many years, the following points must be taken into account.
The cooling circuit should be a closed circuit. For units with an aluminium heat sink, through which the coolant
directly flows, a closed cooling circuit is absolutely essential. This is because only a closed circuit can prevent the
permanent infiltration of the cooling circuit by reactive oxygen and ensure that there is a permanent and stable,
chemical balance in the cooling circuit with aluminium heat sink. For units with heat sinks with an integrated stainless
steel heat exchanger a closed cooling circuit is not essential, but recommended. Under certain conditions, for these
units also open circuits can be used.
The materials used in the cooling circuit must be coordinated with one another so that they do not corrode as a
result of electro-chemical reactions. If units with an aluminium heat sink are used, mixed installations made up of
aluminium, copper, brass and iron should be avoided or, at least, limited. The use of plastics containing halogens
(PVC pipes and seals) should also be avoided. Recommended cooling circuits are closed cooling circuits with pipes
made of high-alloy steel (V2A or V4A) or, alternatively, with pipes made of ABS plastics. For the connections of the
liquid-cooled units to the pipes EPDM hoses should be used. Seals must be chloride, graphite and carbon-free.
The electrical potentials in the cooling circuit must be designed in such a way that no differences between the
electrical potentials of the individual components of the cooling circuit can occur. The rules stated in the section
"EMC-compliant installation for optimized equipotential bonding in the drive system" also apply here, whereby in
liquid-cooled systems not only all electrical components, such as converters and motors, must be fully incorporated in
the equipotential bonding, but also non-electrical components of the cooling circuit, such as pipes, pumps and heat
exchangers. As SINAMICS S120 Liquid-Cooled units are designed for potential-free operation, the grounding of the
units must be done with the largest possible cross-section.
The chemical composition of the coolant for SINAMICS S120 Liquid-Cooled units must be as follows:
Units with aluminium heat sinks, through which the coolant directly flows:
a) Deionised water, i.e. water with reduced electrical conductivity (5.....10 S/cm), such as "battery water" with
0.2 % – 0.25 % Nalco inhibitor 00GE056 or with 20 % - 45 % Antifrogen N anti-freeze, or
b) Filtered drinking/urban water with 20 % - 45 % Antifrogen N anti-freeze, or
c) Drinking or urban water of the quality specified below:
•
pH value
•
Chloride ions
•
Sulpfate ions
•
Nitrate ions
•
Dissolved solides
•
Total hardness
•
Electrical conductivity
•
Size of entrained particles
In addition 0.2 % – 0.25 % Nalco inhibitor 00GE056 or 20 % – 45 % Antifrogen N anti-freeze must be used.
SINAMICS Engineering Manual – May 2008
122/396
© Siemens AG
5.5 to 8.0
< 40 ppm
< 50 ppm
< 50 ppm
< 340 ppm
< 170 ppm
< 500 μS/cm
< 0.1 mm