Electrical Installation Of Motor Cables - Danfoss VLT HVAC Drive FC 102 Design Manual

How to Install
F Frame Requirements
F1/F3 requirements: Motor phase cable quantities must be
multiples of 2, resulting in 2, 4, 6, or 8, to obtain an equal
number 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.
F2/F4 requirements: Motor phase cable quantities must be
multiples of 3, resulting in 3, 6, 9, or 12, to obtain an equal
5 5
number 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.
F8/F9 requirements: 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.
F10/F11 requirements: Motor phase cable quantities must
be multiples of 2, resulting in 2, 4, 6, or 8, to obtain an
equal number 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.
F12/F13 requirements: Motor phase cable quantities must
be multiples of 3, resulting in 3, 6, 9, or 12, to obtain an
equal number 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.
F14 requirements: Motor phase cable quantities must be
multiples of 4, resulting in 4, 8, 12, or 16, to obtain an
equal number 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, a
minimum of 8 ft [2.5 m], and quantity of cables must be
equal from each inverter module to the common terminal
in the junction box.
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Design Guide
NOTICE!
If a retrofit application requires an unequal number of
wires per phase, consult the factory for requirements
and documentation or use the top/bottom entry side
cabinet busbar option.

5.2.3 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, continue the shield at
the lowest possible HF impedance.
Connect the motor cable shield to both the decoupling
plate on the adjustable frequency drive and to the metal
housing on the motor.
Make the shield connections with the largest possible
surface area (cable clamp) using the installation devices in
the adjustable frequency drive.
If it is necessary to split the shield to install a motor
isolator or motor relay, continue the shield with the lowest
possible HF impedance.
Cable-length and cross-section: The adjustable frequency
drive 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. Reduce the cable length accordingly.
Keep the motor cable as short as possible to reduce the
noise level and leakage currents.
Switching frequency: When adjustable frequency drives
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: Do not use aluminum conductors.
Terminals can accept aluminum conductors but the
conductor surface has to be clean and the oxidation
removed and sealed by neutral, acid-free grease before the
conductor is connected.
Additionally, the terminal screw must be retightened after
two days due to the softness of the aluminum. Maintain a
gas tight joint connection to prevent oxidation.
Danfoss A/S © Rev. 2014-01-13 All rights reserved. MG16C122