4.2.4 Extra Protection (RCD)
ELCB, RCD, GFCI relays or multiple protective groundings
are often used as extra protection, or needed to provide
compliance with local safety regulations. In case of a
ground fault, a DC component may develop in the fault
current. Observe local regulations when using ELCB relays.
To reassure effective protection and unintended tripping of
protective relays, all relays must be suitable for protection
of 3-phase equipment with active current infeed and for a
brief discharge during power-up. Use a relay type with
adjustable trip amplitude and time characteristics. Select a
current sensor with sensitivity of more then 200 mA and
not less than 0.1 s operation time.
4.2.5 RFI Switch
Mains supply isolated from ground (IT mains)
If the active filter 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) 1) via
14-50 RFI Filter
on the unit.
For further reference, see IEC 364-3. In OFF mode, the
internal RFI capacities between the chassis and the
intermediate circuit are cut off to avoid damage to the
intermediate circuit. 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).
NOTICE
Marine grids are typically IT type grids.
4.2.6 Torque
Correct torque is imperative for all electrical connections.
Incorrect torque results in a bad electrical connection.
Torque values are provided in
Table 4.3
.
Enclosure size
Torque
Bolt size
D
19 Nm (168 in.-lbs.)
M10
E
19 Nm (168 in.-lbs.)
M10
Table 4.3 Correct Torque Values
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 4.4 Use a Torque Wrench to Tighten the Bolts
4.2.7 Current Transformer (CT)
The filter operates in close loop operation by receiving
current signals for external current transformers. The
received signal is processed and the filter reacts according
to programmed actions.
CAUTION
Incorrect current transformer connection, installation or
configuration leads to unintended and uncontrollable
behaviour of the filter.
NOTICE
The current transformers are not part of the filter
package and must be purchased separately.
CT specification
The active filter supports most CTs. The CTs must have the
following specifications:
Technical specification of active filter, passive CT
RMS
Maximum measured RMS current
Accuracy
0.5% or better (Class 0.5)
Secondary rated
current
1A or 5A (5A is recommended)
Set-up via hardware
Rated frequency
50/60 Hz
Rated power/burden
See
Table 4.5
(AAF burden equals 2 m
Ω
)
Table 4.4 CT Specifications
Electrical Installation
Operating Instructions
18
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MG90V302
4
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