Electrical Installation Of Motor Cables - Danfoss VLT AQUA Drive FC 202 Design Manual

How to Install
continued with the lowest possible HF
impedance.
F-frame requirements
F1/F3 requirements:
Motor phase cable quantities must be multiples of 2,
resulting in 2, 4, 6, or 8 (one cable is not allowed) to
obtain equal numbers of wires attached to both inverter
module terminals. The cables are required to be equal
length within 10% between the inverter module terminals
and the first common point of a phase. The recommended
common point is the motor terminals.
5 5
F2/F4 requirements:
Motor phase cable quantities must be multiples of 3,
resulting in 3, 6, 9, or 12 (1 or 2 cables are not allowed) to
obtain equal numbers of wires attached to each inverter
module terminal. The wires are required to be equal length
within 10% between the inverter module terminals and the
first common point of a phase. The recommended
common point is the motor terminals.
Output junction box requirements:
The length, minimum 2.5 meters, and quantity of cables
must be equal from each inverter module to the common
terminal in the junction box.
NOTICE
If a retrofit application requires unequal numbers of
wires per phase, consult the factory for requirements
and documentation or use the top/bottom entry side
cabinet busbar option.

5.3.6 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 - 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 14-01 Switching Frequency.
Aluminum conductors
Aluminum conductors are not recommended. Terminals
can accept aluminum conductors but the conductor
surface has to be clean, free of oxidation and sealed with
neutral acid free Vaseline grease before the conductor is
connected.
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Design Guide
Furthermore, the terminal screw must be retightened after
two days due to the softness of the aluminum. It is crucial
to keep the connection a gas tight joint, otherwise the
aluminum surface oxidizes again.
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