4.8.7
Operating a converter on the residual current device
WARNING
Live enclosure parts due to unsuitable protection equipment
The frequency inverter can cause a direct current in the protective conductor. If an unsuitable
residual current device (RCD) or residual current monitoring equipment (RCM) is used to
protect against direct or indirect contact, the direct current in the protective conductor prevents
the protective device from being triggered if a fault occurs.
As a result, parts of the inverter without touch protection can carry a dangerous voltage.
● Adhere to the conditions for residual current devices as listed below.
Preconditions for operating the inverter with a residual current device
You can operate the inverter with a residual current device (RCD, ELCB or RCCB) or residual
current monitoring equipment (RCM) under the following conditions:
● The inverter is connected to a TN system.
● You are using an inverter, with frame sizes FSAA, FSA or FSB.
● You are using a super-resistant (universal current-sensitive) RCD/RCM, type B, such as a
SIQUENCE circuit breaker from Siemens.
– RCD/RCM tripping current for filtered devices = 300 mA
– RCD/RCM tripping current for unfiltered devices = 30 mA
● Each inverter is connected via its own RCD/RCM.
● Maximum length of shielded motor cables: 15 m.
● Maximum length of non-shielded motor cables: 30 m.
Measures for touch protection without RCD/RCM
Establish touch protection using one of the following measures:
● Double insulation
● Transformer for isolating the inverter from the line supply
Installing
4.8 Connect the line supply, motor and braking resistor
SINAMICS G120C converter
80
Operating Instructions, 09/2017, FW V4.7 SP9, A5E34263257B AF
