Siemens SINAMICS G120 Hardware Installation Manual page 40

Connecting
Risk of injury due to hot surfaces
During operation and for a short time after the inverter shuts down, the surface of the device
can reach a high temperature.
● During this time, avoid any direct contact with the surface of the inverter.
Protection and monitoring equipment
To provide protection against short-circuit, use the overcurrent devices listed in Technical data
(fuses, circuit breakers etc.).
If the apparent impedance of the line supply at the infeed point is not suitable, so that fuses
do not rupture in the specified time in the case of insulation failure (ground fault, fault to frame),
then you must use additional fault current protective devices RCD (RCCB or MRCD), type B.
In order that an RCD does not unnecessarily trip as a result of operational leakage currents,
the following preconditions must be fulfilled:
● The neutral point of the line supply is grounded.
● For inverters with rated input currents ≤ 125 A referred to LO, use an RCCB type B with a
response limit current of 300 mA. Connect the RCCB in series with the overcurrent
protective devices.
● For inverters with rated input currents> 125 A referred to LO, use a type B MRCD (for
example, from the Bender company).
An MRCD comprises an RCM (differential current monitoring device), a measuring current
transducer and a circuit breaker with additional undervoltage release, listed in the Technical
data. An example of an MRCD design is provided in the following diagram.
Figure 5-1
● A dedicated RCD is used for every inverter.
● The motor cables are shorter than 50 m (164 ft) shielded, or 100 m (328 ft) unshielded.
Additional information about motor cables
40
CAUTION
MRCD
Length of motor cable (Page 47)
PE
Power Module PM230, IP20 / Push-through technology (PT)
Hardware Installation Manual, 08/2016, A5E34331322B AB