Delta VFD-ED Series, User Manual

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Appendix A. EMC Standard Installation Guide | VFD-ED
A-12
Criteria for Earthing System and EMC
TN-S TN-C TT IT
Safety of
Personnel Good
Continuity of the PE
conductor must be
ensured throughout
the installation
Good
Continuity of the PE
conductor must be
ensured throughout
the installation
Good
RCD is
mandatory
Good
Continuity of the PE
conductor must be
ensured throughout
the installation
Safety of
Property Poor
High fault current
(around 1kA)
Poor
High fault current
(around 1kA)
Good
Medium fault
current (< a few
dozen amperes)
Good
Low current at the first
fault (< a few dozen
mA) but high current at
the second fault
Availability
of Energy Good Good Good Excellent
EMC
Behavior Excellent
Few equipotential
Problems:
- Need to handle the
high leaking
currents problem of
the device
- High fault current
(transient
disturbances)
Poor
(prohibited)
- Neutral and PE are
the same
- Circulation of
disturbance currents
in exposed
conductive parts
(high magnetic-field
radiation)
- High fault currents
(transient
disturbances)
Good
- Over-voltage
risk
- Equipotential
Problems:
- Need to handle
the high leaking
currents problem
of the device
- RCD (Residual-
current device)
Poor
(should be avoided)
- Over-voltage risk
- Common–mode
filters and surge
arrestors must handle
the phase-to-phase
voltage.
- RCDs subject to
nuisance tripping
when common-mode
capacitors are
present
- Equivalent to TN
system for second
fault