1.2.7 Environmental Considerations
Drives – both centrally-mounted and distributed in the plant - are exposed to the environment. As motor controls handle high voltages and currents at
the same time they must be protected from dust and humidity so that they do not fail or break down. Both manufacturers and installers must take account
of this and Danfoss Drives have designed the decentralised products with a deep concern in both aspects.
Decentralised motor controls must also meet increasing demands in respect of hygiene levels in pharmaceutical industries and in food- and beverage
production in particular, where drives are exposed to cleaning agents for extensive periods of time, high pressure hosing and the like. The exterior of the
decentralised motor controls must be designed in such a way as to achieve this. Complicated heat sinks as illustrated in the figure must be avoided as it
is difficult to clean and not resistant to common cleaning agents.
Danfoss decentralised drives are designed to meet the requirements as shown in illustration 1.9. There are no hard-to-clean places, blind plugs have no
notches or indentations and two-layer robust surface treatment - tested to withstand commonly used cleaning agents - protects the housing.
Illustration 1.8: Non-cleaning friendly pin fin heat sink versus the easy to clean Danfoss solution
All corners are rounded to prevent dust sticking, and the distance between ribs allows high-pressure air cleaning, hosing and easy cleaning with a brush.
These concerns are more or less irrelevant if not applied to all elements and standard AC motors are normally designed without these concerns in mind
– stressed by integrated fans and cooling ribs both difficult to clean. Danfoss has met the challenge by designing a range of aseptic geared motors. These
motors have no fans and only smooth surfaces. An IP65 enclosure class is standard as is the special CORO coating resistant to acid, alkali and cleaning
agents used in for instance food and beverage industry. See the photo of an example of the aseptic geared motor series in Illustration 1.10.
Illustration 1.9: Aseptic Danfoss geared motor
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 decentralised 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 vapour
VLT
®
Decentral FCD 300 Design Guide
1 The Decentral Concept
MG.90.S1.02 - VLT
®
is a registered Danfoss trademark
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