2 Engineering
2.3 Safety and switching
DC1 Frequency Inverter 10/12 MN04020003Z-EN www.eaton.com 35
2.3.2 Residual current device (RCD)
Residual current devices (RCD) are also known as ground fault circuit inter-
rupters (GFCI) orresidual-current circuit breakers (RCCB).
Residual current devices protect people and farm animals from the presence
(not the production!) of impermissibly high touch voltages.
They prevent
dan-
gerous
(including fatal) injuries caused
by
electrical accidents and also serve
to prevent fires.
Leakage currents to earth are mainly caused by foreign capacities with fre-
quency inverters: between the motor phases and the shielding of the motor
cable and via the star capacitor of the radio interference suppression filter.
￫
Residual current devices must be suitable for:
• the
protection
of
installations
with
DC current component
in
case of fault scenario (RCD, type B),
• high leakage currents (300 mA),
• Briefly diverting surge currents
CAUTION
Only AC/DC sensitive residual current devices (RCD, type B)
may be used with frequency inverters (EN 50178, IEC 755).
Marking on the residual current device
AC/DC sensitive (RCD, part no.
B)
￫
Frequency inverters work internally with rectified AC currents. If
an error occurs, the DC currents can block an RCD safety device
of type A from triggering and therefore disable the protective
functionality.
NOTICE
Residual current devices (RCD) are only to be installed between
the AC power supply network and the frequency inverter.
￫
Safety-relevant leakage currents can occur while handling and
when operating the frequency inverter, if the frequency inverter
is not grounded.
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