4.6 Electrical Installation
4.6.1 Power Connections
Cabling and Fusing
NB!
Cables General
All cabling must comply with national and local regulations on cable cross-sections and ambient temperature. UL applications require
75 °C copper conductors. 75 and 90 °C copper conductors are thermally acceptable for the frequency converter to use in non UL
applications.
The power cable connections are situated as shown below. Dimensioning of cable cross section must be done in accordance with the current ratings and
local legislation. See the
Specifications section
for details.
For protection of the frequency converter, the recommended fuses must be used or the unit must be with built-in fuses. Recommended fuses can be
seen in the tables of the fuse section. Always ensure that proper fusing is made according to local regulation.
The mains connection is fitted to the mains switch if this is included.
NB!
To comply with EMC emission specifications, screened/armoured cables are recommended. If an unscreened/unarmoured cable is used,
see section
Power and Control Wiring for Unscreened Cables
.
See section
General Specifications
for correct dimensioning of motor cable cross-section and length.
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.
Connect the motor cable screen to both the de-coupling 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). This is done by using the supplied installation devices within the
frequency converter.
Cable-length and cross-section:
The frequency converter has been EMC tested with a given length of cable. 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 instruction in par. 14-01
Switching Frequency
.
VLT HVAC Low Harmonic Drive Operating In-
structions 4 How to Install
MG.16.A1.02 - VLT
®
is a registered Danfoss trademark 43
4
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