Ground Leakage - Emerson digitax st series Installation Manual

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
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
Model
DST120X at 220V
DST140X at 400V
The above leakage current is just the leakage current of the drive with the internal EMC filter
NOTE
connected and does not take into account any leakage currents of the motor or motor cable.
With internal EMC filter removed the ground leakage current = <1mA.
In both cases, there is an internal voltage surge suppression device connected to
NOTE
ground. Under normal circumstances, this carries negligible current.
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
2
to 10mm .
WARNING
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
Only type B ELCB / RCD are suitable for use with 3 phase inverter drives.
WARNING
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.
Digitax ST Installation Guide
Issue: 2
3 phase Star 3 phase
ground Delta ground
mA
4 10
12 40
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1 phase
3
17