Danfoss VLT Micro Drive FC 51 Design Manual page 48

How to Install
6.8.2 Motor Cables
See chapter 9 Specifications for maximum dimensioning of
motor cable cross-section and length.
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Use a shielded/armored motor cable to comply
with EMC emission specifications.
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Keep the motor cable as short as possible to
reduce the noise level and leakage currents.
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Connect the motor cable shield to both the
decoupling plate of the frequency converter and
to the metal cabinet of the motor.
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Make the shield connections with the largest
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possible surface area (cable clamp). This is done
by using the supplied installation devices in the
frequency converter.
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Avoid mounting with twisted shield ends
(pigtails), which spoils high frequency shielding
effects.
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If it is necessary to split the shield to install a
motor isolator or motor relay, the shield must be
continued with the lowest possible HF
impedance.
6.8.3 Electrical Installation of Motor Cables
Shielding of cables
Avoid installation with twisted shield ends (pigtails). They
spoil the shielding effect at higher frequencies.
If it is necessary to break the shield to install a motor
isolator or motor contactor, the shield must be continued
at the lowest possible HF impedance.
Cable length and cross-section
The frequency converter has been tested with a given
length of cable and a given cross-section of that cable. If
the cross-section is increased, the cable capacitance, and
thus the leakage current, may increase, and the cable
length must be reduced correspondingly.
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VLT Micro Drive FC 51
Switching frequency
When frequency converters are used together with sine-
wave filters to reduce the acoustic noise from a motor, the
switching frequency must be set according to the sine-
wave filter instruction in parameter 14-01 Switching
Frequency.
Aluminum conductors
Aluminum conductors are not recommended. When using
aluminum conductors, ensure that the conductor surface is
clean and the oxidation is removed and sealed by a
neutral acid-free grease before connecting the conductor.
Retighten the terminal screw after 2 days due to the
softness of aluminum. It is crucial to keep the connection a
gas-tight joint, otherwise the aluminum surface oxidizes
again.
6.8.4 EMC-correct Electrical Installation
General points to be observed to ensure EMC-correct
electrical installation.
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Danfoss A/S © 01/2016 All rights reserved.
Use only shielded/armored motor cables and
shielded/armored control cables.
Connect the shield to ground at both ends.
Avoid installation with twisted shield ends
(pigtails), since this ruins the shielding effect at
high frequencies. Use the cable clamps provided
instead.
It is important to ensure good electrical contact
from the installation plate through the installation
screws to the metal cabinet of the frequency
converter.
Use star washers and galvanically conductive
installation plates.
Do not use unshielded/unarmored motor cables
in the installation cabinets.
MG02K402