Line-side power components
2.4 Line supply connection via residual-current devices
SINAMICS S120 Combi
Manual, Edition 07/2012, 6SL3097-4AV00-0BP3
33
2.4 Line supply connection via residual-current devices
Selectively tripping, AC/DC-sensitive residual-current devices (type B) can be used in
addition to the overcurrent protection devices.
CAUTION
Residual-current devices have to be installed if the line supply conditions in terms of short-
circuit power and loop impedance at the infeed point are not such that the installed
overcurrent protection devices will trip within the prescribed period if a fault occurs. Since
TT line supplies do not generally meet this requirement, residual-current devices must
always be installed for this type of system.
Residual-current operated circuit breakers (RCD)
DANGER
Residual-current operated circuit breakers alone are not permissible to provide protection
against direct and indirect contact.
When using residual-current operated circuit breakers, it should be noted that
● It is only permissible to use a delayed tripping, selective AC/DC-sensitive residual-current
operated circuit breaker, type B.
● The max. permitted grounding resistance of the "selective protective device" is observed
(83 Ω max. for residual-current devices with 0.3 A rated differential current).
● Accessible parts of the Power Drive System and the machine are connected to the
system's protective ground conductor.
● The maximum total length of the shielded power cables in the drive line-up (motor cables
incl. line supply cables from the line filter to the connecting terminals of the S120 Combi)
is 175 m.
● Only recommended line filters must be used during operation.
● Only one residual-current circuit breaker may be connected in series (cascading is not
possible).
● Switching elements (line disconnector, contactors) for connecting and disconnecting the
drive line-up have max. 35 ms delay time time between the closing/opening of the
individual main contacts.
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