21
VLT
®
3500 HVAC
MG.35.B1.02 – VLT is a registered Danfoss trademark
Section 1Section 1Section 1Section 1Section 1
Section 2Section 2Section 2Section 2Section 2
Section 3Section 3Section 3Section 3Section 3
Section 4Section 4Section 4Section 4Section 4
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Cable for serial communication
The cable for serial communication should be
screened.
The screen should be installed using a clamp on the
VLT frequency converter (see the instructions for in-
stallation, pp.
pp.
pp.
pp.
pp. 21-22, item B).
With regard to cable specifications and instructions
for installation in general, reference is made to the
PROFIBUS product manual.
Equalising currents
Efforts should be made to avoid possible equalising
currents that may occur when the control cable
screen is connected to the chassis (earthed) at both
ends. Equalising currents occur because of voltage
differences between the VLT frequency converter
chassis and the chassis of the controlling device.
They can be avoided by making a tight fit with the
cabinet chassis rear plate, thereby ensuring that any
equalising currents will run via the chassis rear plates
and their joints, not via the cable screens.
Control cables
Control cables should be screened. The screen
should be connected using a clamp to the VLT
frequency converter chassis (see the instructions for
installation, pp. 21-22, item C). Normally, the screen
should also be connected to the PLC or similar of the
controlling device (follow the instructions for use of the
device in question).
In connection with very long control cables and
analogue signals, 50 Hz ripple loops may occur in rare
cases, depending on the installation. This is because
of interference coupling from the mains supply cables.
In this connection it can be necessary to break the
screen or possible insert a 100 nF capacitor between
screen and chassis.
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2.6 EMC corr
ect installation
VLT 3502-3511
