Danfoss 176F7300 Manual page 82

EMC-correct Electrical Installation
General points to be observed to ensure EMC-correct electrical installation:
- Use only shielded motor cables and shielded control cables.
NOTE: Suggested shielded cable type, like that supplied by Southwire.
- Connect the shield to ground at both ends.
- PG Cable Glands, of the type shown below, are recommended. Avoid installation with
twisted shield ends (pigtails), since this ruins the shielding effect at high frequencies.
NOTE: Suggested cable gland, "Jacob PG", supplied by ALTECH.
- It is important to ensure good electrical contact from the installation plate through the
installation screws to the metal cabinet of the VLT adjustable frequency drive.
- Use toothed washers and galvanically conductive installation plates.
- DO NOT use unshielded motor cables in the installation panels.
The installer is responsible for the final EMC properties and compliance with the Low
Voltage Directive for the installation.
Use of EMC-correct cables
Shielded/armored cables are recommended to optimize EMC immunity of the control
cables and the EMC emission from the motor cables. The ability of a cable to reduce the
in- and outgoing radiation of electric noise depends on the transfer impedance (Z
shield of a cable is normally designed to reduce the transfer of electric noise; however, a
shield with a lower Z value is more effective than a shield with a higher Z
T
stated by cable manufacturers, but it is often possible to estimate Z
physical design of the cable. Z
• The conductibility of the shield material.
• The contact resistance between the individual shield conductors.
• The shield coverage, i.e. the physical area of the cable covered by the shield - often
stated as a percentage value.
• Shield type, i.e. braided or twisted pattern.
can be assessed on the basis of the following factors:
T
80
VLT ® MICRO
). The
T
. Z is rarely
T T
by assessing the
T