Danfoss VLT 8000 AQUA series Operating Instructions Manual page 183

Earth leakage current
Earth leakage current is primarily caused by the
capacitance between motor phases and the motor
cable screen. See drawing on the following page.
The size of the leakage current to the earth depends
on the following factors, in order of priority:
1. Length of motor cable
2. Motor cable with or without screen
3. Switching frequency
4. RFI filter used or not
5. Motor earthed on site or not
The leakage current is of importance to safety during
handling/operation of the frequency converter if (by
mistake) the frequency converter has not been earthed.
MG.83.A2.02 - VLT is a registered Danfoss trademark
NB!:
RCD
Since the leakage current is > 3.5 mA, reinforced
earthing/grounding must be established, which
is required if EN 50178 is to be complied with. Never
use ELCB relays (type A) that are not suitable for DC
fault currents from three-phase rectifier loads.
If ELCB relays are used, they must be:
- Suitable for protecting equipment with a direct
current content (DC) in the fault current
(3-phase bridge rectifier)
- Suitable for power-up with short pulse-shaped
charging current to earth
- Suitable for a high leakage current (300 mA)
Leakage currents to earth
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VLT 8000 AQUA
183