Grounding - Danfoss VLT Refrigeration Drive FC 103 Operating Instructions Manual

Electrical Installation
Screening of cables
Avoid installation with twisted screen ends (pigtails). They
spoil the screening effect at higher frequencies. If breaking
the screen is necessary to install a motor isolator or
contactor, continue the screen 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). Use the installation devices
within the frequency converter.
Cable-length and cross-section
The frequency converter has been EMC-tested with a given
cable length. To reduce the noise level and leakage
currents, keep the motor cable as short as possible.
Switching frequency
When frequency converters are used with sine-wave filters
to reduce the acoustic noise from a motor, set the
switching frequency according to
parameter 14-01 Switching Frequency.
Termi 96 97 98 99
nal
numb
er
Motor voltage 0–100% of mains
U V W PE 1) voltage.
3 wires out of motor
U1 V1 W1 Delta-connected
1)
PE
W2 U2 V2 6 wires out of motor
Star-connected U2, V2, W2
U1 V1 W1 PE 1) U2, V2, and W2 to be interconnected
separately.
Table 4.1 Terminal Connections
1) Protective earth connection
Motor
U V W
2 2 2
U V W
1 1 1
FC
96 97 98
Illustration 4.2 Y and Delta Terminal Configurations
MG16N102
Operating Instructions
Motor
U V W
2 2 2
V W
U
1 1
1
FC
96 97 98
Danfoss A/S © 08/2015 All rights reserved.

4.4 Grounding

WARNING
GROUNDING HAZARD!
For operator safety, it is important to ground the
frequency converter properly in accordance with national
and local electrical codes as well as instructions
contained within this document. Do not use conduit
connected to the frequency converter as a replacement
for proper grounding. Ground currents are higher than
3.5 mA. Failure to ground the frequency converter
properly could result in death or serious injury.
NOTICE
It is the responsibility of the user or certified electrical
installer to ensure correct grounding of the equipment in
accordance with national and local electrical codes and
standards.
•
Follow all local and national electrical codes to
ground electrical equipment properly.
•
Establish proper protective earthing for
equipment with ground currents higher than 3.5
mA, see chapter 4.4.1 Leakage Current (>3.5 mA).
•
A dedicated ground wire is required for input
power, motor power, and control wiring.
•
Use the clamps provided with the equipment for
proper ground connections.
•
Do not ground one frequency converter to
another in a "daisy chain" fashion.
•
Keep the ground wire connections as short as
possible.
•
Using high-strand wire to reduce electrical noise
is recommended.
•
Follow motor manufacturer wiring requirements.
4.4.1 Leakage Current (>3.5 mA)
Follow national and local codes regarding protective
earthing of equipment with a leakage current >3.5 mA.
Frequency converter technology implies high frequency
switching at high power. This generates a leakage current
in the ground connection. A fault current in the frequency
converter at the output power terminals might contain a
DC component, which can charge the filter capacitors and
cause a transient ground current. The earth leakage
current depends on various system configurations
including RFI filtering, screened motor cables, and
frequency converter power.
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