74 Unidrive M / HS Frame 7 to 10 Power Installation Guide
This software overload protection should be used in addition to an external overload protection
device.
4.10 Ground leakage
The ground leakage current depends upon whether the internal EMC filter is installed. The drive is
supplied with the filter installed.
With internal filter installed:
56 mA AC at 400 V 50 Hz (proportional to supply voltage and frequency)
18 µA DC with a 600 V DC bus (33 M)
With internal filter removed*:
<1mA
Note that in both cases there is an internal voltage surge protection device connected to ground.
Under normal circumstances this carries negligible current.
*Please note that the internal filter is not removable on size 9E and 10E.
4.10.1 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 with an ELCB / RCD, a delay of at least 50 ms 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 energized simultaneously.
When the internal filter is installed the leakage current is high. In this case a permanent
fixed ground connection must be provided, or other suitable measures taken to prevent a
safety hazard occurring if the connection is lost.
Only type B ELCB / RCD are suitable for use with 3 phase inverter drives.
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