36 Mentor MP Short Form Guide
www.controltechniques.com Issue Number: 5
4.1.1 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
• Types A and AC should never be used with Mentor MP drives.
• Type B must be used with all Mentor MP drives.
If an external EMC filter is used, 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.
4.2 Ground connection
The drive must be connected to the system ground of the AC supply. The ground wiring
must conform to local regulations and codes of practice.
Figure 4-2 Location of ground connection on size 1 drives
Only type B ELCB / RCD are suitable for use with Mentor MP drives.
Electrochemical corrosion of grounding terminals
Ensure that grounding terminals are protected against corrosion i.e. as could be
caused by condensation.
Ground loop impedance
The ground loop impedance must conform to the requirements of local safety
regulations. The drive must be grounded by a connection capable of carrying the
prospective fault current until the protective device (fuse, etc,) disconnects the AC
supply. The ground connections must be inspected and tested at appropriate intervals.
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