
Installation
vacon • 53
Local contacts: http://drives.danfoss.com/danfoss-drives/local-contacts/
5
5.2
Cooling
Instead of using air for cooling, VACON
®
NX Liquid-Cooled drives are cooled with liquid. The liquid
circulation of the drive is usually connected to a heat-exchanger (liquid-liquid/liquid-air) which
cools down the liquid circulating in the cooling elements of the drive. Because the cooling elements
are made of aluminium, the cooling agents allowed to be used are drinking water, demineralized
water or a mixture of water and glycol.
There are two types of circulation system: open systems and closed systems.
An open system has no pressure, and allows free contact with air.
In a closed system, the piping is completely air-tight and there is pressure inside the pipes. The
pipes must be made of metal, or specific plastic or rubber that includes an oxygen barrier.
Preventing of oxygen diffusion in the coolant diminishes the risk of electrochemical corrosion of the
metal parts, and generation of rust deposits. Always use a closed system with VACON
®
NX Liquid-
Cooled drives.
In case there is no other option than using an open system, you must take several precautions.
1.
Use glycol and inhibitor in the coolant.
2.
Examine the water quality regularly, and add inhibitor accordingly.
3.
Yearly check that the properties of the cooling liquid are in accordance with the
specification in this manual.
In a closed circulation system, the following figures are recommended reference values. To avoid
electrochemical corrosion, it is necessary to add an inhibitor (e.g. Cortec VpCI-649) in the cooling
agent.
Add inhibitor to the cooling agent every 2 years and change the cooling agent every 6 years.
The addition of each 0.05% of VpCI-649 into the cooling agent increases the electrical conductivity
with 75-100 μS. The maximum value depends on the added dosage rate.
The heat-exchanger delivered by VACON
®
(HX) consists of stainless steel materials. The good
corrosion performance of stainless steel in district water systems is utilized and no disadvantage of
divergent metal filler is included. Nevertheless, some precautions must be taken to reduce the
corrosion risk on the stainless steel in high chloride waters, see Table 18. We recommend to use a
VACON
®
HX heat exchanger whenever possible.
NOTE!
If no heat-exchanger is used, actions must be taken to avoid electrochemical corrosion.
Specifically no brass or copper elements may be used in the liquid circulation of the drive.
Copper and brass may be used in the liquid circulation in case the liquid-cooled drive is equipped
with a nickel coated aluminum heatsink.
Specification: Drinking water
The attached table gives the chemical requirements for drinking water provided for by the Finnish
Ministry of Social Affairs and Health. These values are indicative.
Table 16. Drinking water chemical specification
Quality
Unit
Value
Acrylamide
μg/l
0.10
Antimony
μg/l
5.0
Arsenic
μg/l
10
Benzene
μg/l
1.0
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