Delta Electronics VFD037CH23A-21 — преимущества и недостатки IT систем в электрооборудовании [631/638]
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Delta Electronics VFD037CH23A-21 — преимущества и недостатки IT систем в электрооборудовании [631/638]

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Delta Electronics VFD037CH23A-21 [631/638] It the neutral point of the transformer and electrical equipment are not earthed only the equipment frames pe are earthed in the it network the power distribution system neutral is either not connected to earth or is earthed via a high impedance in such a system an insulated monitoring device is used for impedance monitoring a built in filter should be disconnected by the rfi jumper and an external filter should not be installed when the ac motor drive or the ac servo motor drive is connected to an it system
8
IT system
IT: The neutral point of the transformer and electrical equipment are not earthed, only the equipment
frames PE are earthed.
In the IT network, the power distribution system Neutral is either not connected to earth or is earthed via a
high impedance. In such a system, an insulated monitoring device is used for impedance monitoring.
A built-in filter should be disconnected by the RFI-jumper and an external filter should not be installed
when the AC motor drive or the AC servo motor drive is connected to an IT system.
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

Содержание

1610

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