VLT® 5000 Crane
Installation
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Earthing of Braided Screened/armoured
Control Cables
Generally speaking, control cables must be braided screened/armoured and the screen must be connected
by means of a cable clamp at both ends to the metal cabinet of the unit.
The drawing below indicates how correct earthing is carried out and what to be done if in doubt.
1.
Correct earthing
Control cables and cables for serial
communication must be fitted with cable
clamps at both ends to ensure the best
possible electrical contact.
2.
Wrong earthing
Do not use twisted cable ends (pig-
tails), since these increase the screen
impedance at high frequencies.
3.
Protection with respect to earth potential
between PLC and frequency converter
If the earth potential between the frequency
converter and the PLC (etc.) is different, electric
noise may occur that will disturb the whole system.
This problem can be solved by fitting an equalising
cable, to be placed next to the control cable.
Minimum cable cross-section: 16 mm
2
4.
For 50/60 Hz earth loops
If very long control cables are used,
50/60 Hz earth loops may occur. This problem can
be solved by connecting one end of the screen to
earth via a 100nF capacitor (keeping leads short).
5.
Cables for serial communication
It is recommended to use twisted-pair
cables to reduce the differential mode interference
between the conductors.
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Safety Earthing
NB!:
The frequency converter has a leakage
current and must be earthed appropriately
for safety reasons. Use earth terminal,
which enables reinforced earthing.
Apply national safety regulations.
MG.50.N4.02 - VLT is a registered Danfoss trademark
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