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Special conditions
Extreme environments
An adjustable frequency drive contains a number
of mechanical and electronic components which
are vulnerable to environmental impact.
Do not install the adjustable frequency drive
in environments where liquids, particles
or gases in the air would damage the
electronics of the drive. Take all necessary measures
to protect the drive. There is a risk of fault trips
and reduced service life of the drive.
Liquids carried through the air can condense in the
adjustable frequency drive. Liquids may facilitate
galvanic corrosion of components and metal parts.
Steam, oil and brine may also cause corrosion of
components and metal parts. In these areas, it
is recommended to install units in cabinets. As a
minimum, cabinets should meet NEMA 12.
Particles in the air, such as dust, may lead to
mechanical, electrical and thermal faults in the
adjustable frequency drive. A typical indicator
of too many particles in the air is dust around
the fan. In very dusty areas, mounting the drive
in a cabinet is recommended. As a minimum,
cabinets should meet NEMA 12.
Aggressive gases, such as sulfur, nitrogen and
chlorine compounds, together with high humidity and
temperature, facilitate possible chemical processes
on the components of the adjustable frequency
drive. These chemical processes quickly damage the
electronics. In these areas, mounting in a cabinet with
fresh-air circulation is recommended, thereby ensuring
that aggressive gases are kept away from the drive.
NOTE
Installation of adjustable frequency drives
in extreme environments increases the risk
of down-time, and considerable reduction
of the service life of the drive.
Before the adjustable frequency drive is installed, check
whether there are liquids, particles or gases in the air.
Examine existing installations in the same environment.
Typical indicators of harmful airborne liquids are water or
oil on metal parts or corrosion. Too many dust particles
are typically observed on top of cabinets. Indication
94
VLT® 2800 Series
of aggressive gases in the air are black copper rails
and cable ends on existing electrical installations.
Galvanic isolation (PELV)
PELV (Protective Extra-Low Voltage) separation is
achieved with galvanic separators between control
circuits and circuits connected to the AC line potential.
These separators meet the requirements for increased
isolation in standard EN 50 178. Installation must be in
accordance with local and national PELV regulations.
All control terminals, terminals for serial communication
and relay terminals are safely separated from the
AC line potential, i.e. they comply with the PELV
requirements. Circuits that are connected to control
terminals 12, 18, 19, 20, 27, 29, 33, 42, 46, 50, 55,
53 and 60 are galvanically connected to one another.
Serial communication connected to terminals 67 -
70 is galvanically isolated from the control terminals,
although this is only a functional isolation.
The relay contacts in terminals 1 - 3 are separated
from the other control circuits with increased isolation,
i.e. these comply with PELV even if there is AC
line potential in the relay terminals.
The circuit elements described below form the safe
electric separation. They fulfill the requirements
for increased isolation and associated testing
pursuant to EN 50 178.
1. Optical isolation between basic motor control
and control card.
2. Optical isolation between basic motor control
and control card.
3. Isolation between the control card and
the power part.
4. Relay contacts and terminals relating to other
circuits on the control card.
PELV isolation of the control card is guaranteed
under the following conditions:
- TT network with maximum 300 Vrms between
phase and ground.
- TN network with maximum 300 Vrms between
phase and ground.
-
IT network with maximum 400 Vrms between
phase and ground.
At higher voltages only SELV is achieved.
MG.28.A8.22 - VLT is a registered Danfoss trademark
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