Danfoss VLT HVAC Drive FC 100 Series Design Manual page 80

5. How to Install
5.2.3. Electrical Installation of Motor Cables
Screening of cables
Avoid installation with twisted screen ends (pigtails). They spoil the screening effect at higher frequencies.
If it is necessary to break the screen to install a motor isolator or motor contactor, the screen 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.
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
Aluminium conductors
Aluminium conductors are not recommended. Terminals can accept aluminium conductors but the conductor surface has to be clean and the oxidation
5
must be removed and sealed by neutral acid free Vaseline grease before the conductor is connected.
Furthermore, the terminal screw must be retightened after two days due to the softness of the aluminium. It is crucial to keep the connection a gas tight
joint, otherwise the aluminium surface will oxidize again.
5.2.4. Removal of Knockouts for Extra Cables
1. Remove cable entry from the frequency converter (Avoiding foreign parts falling into the frequency converter when removing knockouts)
2. Cable entry has to be supported around the knockout you intend to remove.
3. The knockout can now be removed with a strong mandrel and a hammer.
4. Remove burrs from the hole.
5. Mount Cable entry on frequency converter.
5.2.5. Enclosure Knock-outs
Illustration 5.2: Cable entry holes for enclosure B1. The suggested use
of the holes are purely recommendations and other solutions are pos-
sible.
Illustration 5.3: Cable entry holes for enclosure B2. The suggested use
of the holes are purely recommendations and other solutions are pos-
sible.
80
Par. 14-01.
Illustration 5.4: Cable entry holes for enclosure C1. The suggested use
of the holes are purely recommendations and other solutions are pos-
sible.
Illustration 5.5: Cable entry holes for enclosure C2. The suggested use
of the holes are purely recommendations and other solutions are pos-
sible.
MG.11.B7.02 - VLT ® is a registered Danfoss trademark
®
VLT HVAC Drive Design Guide