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Electrical contact can cause galvanic corrosion under
wet or humid conditions. This can occur between
housing (Aluminium) and screws (stainless steel). One
possible consequence is that screws become stuck
and therefore impossible to unfasten in a maintenance
situation. Galvanic corrosion will not be found on
Danfoss decentralized products, as the housings
are fully coated and nylon washers underneath
the screws protects the coating. The complete
coating and the unique gasket design prevent pitting
corrosion, which can occur under gaskets.
Tightly enclosed equipment is susceptible to water
build-up inside the enclosure. This is especially the case
where equipment is exposed to ambient temperature
differences under wet conditions. As a decreasing
ambient temperature lowers the surface temperature
inside the enclosure, water vapor tends to condensate.
At the same time pressure inside the enclosure will
drop and cause humid air from the outside to penetrate
non-hermetic polymer gasket materials and cable
glands. When the enclosure heats up again, only the
vaporized water will escape, leaving more and more
condensed water inside the enclosure. This can lead
to water build-up inside the enclosure and eventually
cause malfunction. The phenomenon is illustrated in
the figure, with a cyclic temperature fluctuation.
The pumping effect in tight enclosures
Build-up of water inside enclosures can be prevented
by membranes that prevents fluids to penetrate but
allows for vapor to pass, as known from fabrics used for
outdoor clothing. A special cable gland with this kind of
12
Decentral Solutions
material is offered by Danfoss to eliminate this problem.
The cable gland should be used in applications
exposed to frequent temperature fluctuations and
humid environments as in equipment used only during
daytime where the inside temperature tends to fall to
the ambient temperature during the night.
Installation flexibility
Danfoss decentralized solutions offers exceptional
installation flexibility. Flexibility is supported
by a number of benefits:
•
Mountable on Danfoss geared motors
•
Decentralized panel mounting possible
•
Handheld control panels
•
PC software for configuring and logging
•
Single or double-sided installation
•
Service switch optional
•
Brake chopper and resistor optional
•
External 24 V backup supply optional
•
M12 connections for external sensors optional
•
Han 10E motor connector optional
•
Fieldbus support (Profibus DP V1, DeviceNet,
As-Interface)
•
Compatibility with standard AC supply systems
(TN, TT, IT, delta grounded)
For further details see the chapter on The
decentralized product range.
MG.90.F2.22 - VLT is a registered Danfoss trademark
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