3.5.2 Grounding
The following basic issues need to be considered when
installing a frequency converter, so as to obtain electro-
magnetic compatibility (EMC).
•
Safety grounding: The frequency converter has a
high leakage current and must be grounded
appropriately for safety reasons. Apply local
safety regulations.
•
High-frequency grounding: Keep the ground wire
connections as short as possible.
Connect the different ground systems at the lowest
possible conductor impedance. The lowest possible
conductor impedance is obtained by keeping the
conductor as short as possible and by using the greatest
possible surface area.
The metal cabinets of the different devices are mounted
on the cabinet rear plate using the lowest possible HF
impedance. This avoids having different HF voltages for
the individual devices and avoids the risk of radio
interference currents running in connection cables that
may be used between the devices. The radio interference
has been reduced.
To obtain a low HF impedance, use the fastening bolts of
the devices as HF connection to the rear plate. It is
necessary to remove insulating paint or similar from the
fastening points.
3.5.3 Extra Protection (RCD)
ELCB relays, multiple protective earthing or earthing can
be used as extra protection, provided that local safety
regulations are complied with.
In case of an ground fault, a DC component may develop
in the fault current.
If ELCB relays are used, local regulations must be observed.
Relays must be suitable for protection of 3-phase
equipment with a bridge rectifier and for a brief discharge
on power-up.
See also
Special Conditions
in the
Design Guide
.
3.5.4 RFI Switch
Mains supply isolated from earth
If the frequency converter is supplied from an isolated
mains source ( IT mains, floating delta and grounded delta)
or TT/TN-S mains with grounded leg, the RFI switch is
recommended to be turned off (OFF) via
14-50 RFI Filter
on
the frequency converter and
14-50 RFI Filter
on the filter.
For further reference, see IEC 364-3. In case optimum EMC
performance is needed, parallel motors are connected or
the motor cable length is above 25 m, it is recommended
to set
14-50 RFI Filter
to [ON].
In OFF, the internal RFI capacities (filter capacitors)
between the chassis and the intermediate circuit are cut
off to avoid damage to the intermediate circuit and to
reduce the earth capacity currents (according to IEC
61800-3).
Also refer to the application note
VLT on IT Mains
It is
important to use isolation monitors that are capable for
use together with power electronics (IEC 61557-8).
3.5.5 Torque
When tightening all electrical connections it is very
important to tighten with the correct torque. Too low or
too high torque results in a bad electrical connection. Use
a torque wrench to ensure correct torque.
176F
A247.12
Nm/in-lbs
-DC 88
+DC 89
R/L1 91
S/L2 92
T/L3 93
U/T1 96
V/T2 97
W/T3
Illustration 3.63 Tightening Bolts with a Torque Wrench
Enclosure
types
Terminal
Torque [Nm] (in-lbs) Bolt size
D
Mains
Motor
19-40
(168-354)
M10
Load sharing
Brake
8.5-20.5
(75-181)
M8
E
Mains
Motor
Load sharing
19-40
(168-354)
M10
Brake
8.5-20.5
(75-181)
M8
How to Install
VLT
®
Automation Drive FC 300 Operating Instructions
54
MG33U402 - Rev. 2013-12-16
3
3
Summary of Contents for VLT AutomationDrive FC 302
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