Cooling Circuit And Coolant Requirements - Siemens SINAMICS G130 Engineering Manual

Cooling circuit and coolant requirements for mixed configurations consisting of units which have a heat sink made
either of stainless steel or aluminum are equally as stringent as the requirements applicable to configurations
comprising units which all have an aluminum heat sink.
The heat sink of the most liquid-cooled units is equipped with power unit components on both sides. These include
the power semi-conductors of the rectifier and the inverter, the DC link capacitors and the symmetrizing resistors of
the DC link. Consequently, the power losses of all the main components are absorbed by the coolant. Only the very
small power losses of the electronic boards and the busbars are dissipated into the ambient air (see table above).
The Control Unit required to operate the devices is not an integral component of the Power Modules.
The functionality of the liquid-cooled units corresponds to that of the corresponding air-cooled units. This includes
overload capacity, factory-set pulse frequency, current derating factors for increased pulse frequencies, possibility of
parallel connection of up to four identical power units and derating factors for the parallel configuration. Exception:
Motor Modules that are specially designed for applications with highly dynamic loads such as, for example, servo
presses: 6SL3320-1TE41-4AS3 and 6SL3325-1TE41-4AS3.
All air-cooled system components of air-cooled units can also be used for the liquid-cooled variants. These include
power components, such as line-side or motor-side reactors and filters (except for the line filters according to
category C2 and the Braking Modules which can be used only in air-cooled units due to their cooling principle), as
well as electronic components such as Communication Boards, Terminal Modules and Sensor Modules.
1.16.3

Cooling circuit and coolant requirements

The coolant required for liquid-cooled SINAMICS S120 units is a mixture of water and anti-freeze. Electro-chemical
processes can occur in the cooling circuit and cause corrosion. These processes depend on a number of 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, biocides)
In order to prevent these corrosive, electro-chemical processes, or at least keep them to an absolute minimum and
so ensure 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.
A closed cooling circuit is absolutely essential for units with an aluminum heat sink. This is because only a
closed circuit can ensure complete separation between the coolant and the surrounding atmosphere and so prevent
infiltration of reactive oxygen into the cooling circuit. Only in this way can it be ensured that there is a continuous and
stable chemical balance in the cooling system.
The closed system is recommended for units with a stainless steel heat sink. Under certain boundary
conditions concerning the water quality, open systems can also be used for units of this kind, see section "The
chemical composition of the coolant".
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 aluminum heat sink are used, mixed installations made up of
aluminum, 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. Insulating EPDM hoses with
an electrical resistance of > 10
Semperit. Seals must be free of chloride, graphite and carbon.
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 it is not only necessary to fully incorporate all electrical components such as transformer,
converter and motor into the equipotential bonding system, but also non-electrical components of the cooling circuit,
such as pipes, pumps and heat exchangers. As liquid-cooled SINAMICS S120 units are designed for potential-free
operation, the grounding of the units must be done with the largest possible cross-section.
Fundamental Principles and System Description
9
Ω/m must be used to make hose connections, e.g. Semperflex FKD supplied by
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