Danfoss VLT AAF00x, Инструкция по эксплуатации

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NOTE!
The accuracy of the CT depends on the wire type and
length of the cable between filter and current transformer.
The required (minimum) CT burden can be calculated as:
[VA] = 25*[Ohm/M] *[M]+1.25
[Ohm/M] being the cable resistance in Ohm/meter, [M]
being the cable length in meters
Table 4.5 shows the minimum CT burden for different wire
gauge at wire length of 164 ft [50 m] and standard wire
resistance value:
Wire Gauge
[mm2 / AWG]
Resistance
[Ohm/Km] Wire length
[meters / feet]
Minimum CT
burden [VA]
1.5 / #16 13.3 50 / 164 >16.6
2.5 / #14 8.2 50 / 164 >10.2
4 / #12 5.1 50 / 164 > 6.3
6 / #10 3.4 50 / 164 > 4.2
10 / #8 2 50 / 164 > 2.5
Table 4.5 Minimum CT Burden
For a fixed CT burden, the maximum allowed wire length
can be calculated as:
[M] = ([VA]-1.25) / (25*[Ohm/M])
Below is the maximum wire length of CT with 2.5mm
2
wires and resistor value equal 8.2 Ohm/km:
Wire Gauge
[mm2 / AWG]
Resistance
[Ohm/Km] Minimum CT
burden [VA]
Wire length
[meter / feet]
2.5 / #14 8.2 5 <18m / 60
2.5 / #14 8.2 7.5 <30m / 100
2.5 / #14 8.2 10 <42m / 140
2.5 / #14 8.2 15 <67m / 220
2.5 / #14 8.2 30 <140m / 460
Example
Calculation example for correct current transformer for an
application with:
RMS= 653Amp, Distance between filter and CTs of 98 ft
[30 m].
RMS=653*1.1= 719A, CT RMS = 750Amp. Burden :
30m@2.5mm
2 wire => 25*0.0082*30+1.25=7.4 => 7.5 [VA].
Current transformer installation
The unit only supports three CT installations. External CTs
should be installed on all three phases to detect the
harmonic content of the grid. The flow direction of the
sensor is in most cases indicated by an arrow. The arrow
should point in the direction of the current flow and thus
towards the load. If the flow direction is programmed
incorrectly, the polarity can be changed via filter
300-25 CT
Polarity . 300-25 CT Polarity can program the polarity of all
three phases individually.
L1
L2
L3
K L
K L
K L
K L
K L
K L
1
2
91 92 93
L1 L2 L3
95
130BB510.11
1 or 5 Amp CT Set-up
To allow for possible reuse of already present CT
transformers, the VLT Active Filter allows use of either 1
Amp or 5 Amp CTs. The filter is as standard set-up for 5
Amp CT feedback. If the CTs are 1 Amp, redirect the CT
terminal plug from slot MK101, pos. 1, to MK108, pos. 2,
on the AFC card; see
Figure 4.29 .
130BB950.10
1
3
4
5
6
2
Figure 4.29 AFC Board
Individual or group compensation
The compensation of the filter depends on the signal that
is returned from the current transformers. The point of
installation for these sensors thus determines the loads
that are corrected.
How to Install VLT Active Filter AAF 00x
MG.90.V2.22 - VLT
®
is a registered Danfoss trademark 4-23
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