Specifications

5.2.2 Motor Cables
See 8 General Specifications and Troubleshooting for
maximum dimensioning of motor cable cross-section and
length.
•
Use a screened/armoured motor cable to comply
with EMC emission specifications.
•
Keep the motor cable as short as possible to
reduce the noise level and leakage currents.
•
Connect the motor cable screen to both the
decoupling plate of the frequency converter and
the metal cabinet of the motor.
•
Make the screen connections with the largest
possible surface area (cable clamp) using the
installation devices in the frequency converter.
•
Avoid mounting with twisted screen ends
(pigtails), which will spoil high frequency
screening effects.
•
If it is necessary to split the screen to install a
motor isolator or motor relay, the screen must be
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, 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
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, 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 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
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, continue the screen at
the lowest possible HF impedance.
Connect the motor cable screen to both the decoupling
plate of the frequency converter and to the metal housing
of the motor.
Make the screen connections with the largest possible
surface area (cable clamp) using the installation devices in
the frequency converter.
If it is necessary to split the screen to install a motor
isolator or motor relay, continue the screen with 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. Reduce the cable length accordingly. Keep the
motor cable as short as possible to reduce the noise level
and leakage currents.
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.
How to Install VLT® HVAC Drive FC 102 Design Guide
100 MG16C102 - Rev. 2013-08-20
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