Emerson digitax st series, Руководство по установке, Страница: 17 / 28

Digitax ST Installation Guide
17
Issue: 2 www.controltechniques.com
Sa
fe
ty
Informa
tio
n
Introd
uction
M
ec
han
ical Inst
allatio
n
El
ectrical
Inst
allati
o
n
4.2 Ground leakage
The ground leakage current depends upon whether the internal EMC filter is installed.
The drive is supplied with the filter installed. Instructions for removing the internal filter
are given in Figure 4-2.
With the internal EMC filter fitted the ground leakage current is as follows:
Table 4-2 Ground leakage current with internal EMC filter fitted
With internal EMC filter removed the ground leakage current = <1mA.
4.2.1 Use of residual current device (RCD)
There are three common types of ELCB / RCD:
1. AC - detects AC fault currents
2. A - detects AC and pulsating DC fault currents (provided the DC current reaches
zero at least once every half cycle)
3. B - detects AC, pulsating DC and smooth DC fault currents
• Type AC should never be used with drives
• Type A can only be used with single phase drives
• Type B must be used with three phase drives
If an external EMC filter is used, a delay of at least 50ms should be incorporated to
ensure spurious trips are not seen. The leakage current is likely to exceed the trip level
if all of the phases are not energised simultaneously.
Fuses/MCB
The AC supply to the drive must be installed with suitable protection against overload
and short circuits. Failure to observe this requirement will cause risk of fire.
WARNING
The drive must be grounded by a conductor sufficient to carry the prospective fault
current in the event of a fault. See also the warning in section 4.2
Ground leakage
relating to ground leakage current.
WARNING
Model
3 phase Star
ground
3 phase
Delta ground
1 phase
mA
DST120X at 220V 4 10 3
DST140X at 400V 12 40
The above leakage current is just the leakage current of the drive with the internal EMC filter
connected and does not take into account any leakage currents of the motor or motor cable.
NOTE
In both cases, there is an internal voltage surge suppression device connected to
ground. Under normal circumstances, this carries negligible current.
NOTE
When the internal EMC filter is installed, the leakage current is high. In this case, a
permanent fixed ground connection must be provided with a cross sectional area equal
to 10mm
2
.
WARNING
Only type B ELCB / RCD are suitable for use with 3 phase inverter drives.
WARNING