Requirements For Branch Circuit Protection; Operation With Residual Current Protective Device (Rcd) - Siemens SINAMICS G115D Operating Instructions Manual

Wiring

4.4 Requirements for branch circuit protection

4.4 Requirements for branch circuit protection
Requirements for UL-compliant installation
The integral solid-state short-circuit protection does not provide branch circuit protection.
Branch circuit protection must be provided in accordance with the National Electrical Code
and any additional local codes.
4.5

Operation with residual current protective device (RCD)

Fire or electric shock due to unsuitable residual-current protective devices
The converter may create a current through the protective conductor. The current through
the protective conductor can cause the residual current device (RCD) or residual current
monitor (RCM) to incorrectly trip (nuisance trip). In the case of a ground fault, the fault
current can contain a DC component, which prevents the RCD or RCM from tripping, with
the risk of subsequent fire or electric shock.
• Use the protection and monitoring devices recommended in the documentation.
Protection and monitoring equipment
To provide protection against short-circuit, use the recommended overcurrent protective
devices (fuses, circuit breakers etc.).
Branch protection and short-circuit strength according to UL and IEC
(https://support.industry.siemens.com/cs/ww/en/ps/27867)
If the earth fault loop impedance of the line supply at the infeed point is too high to ensure
that the overcurrent protective device disconnects within the stipulated time in the case of
insulation failure (ground fault, fault to frame), then you must use additional residual current
protective devices RCD, 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.
• A dedicated RCD is used for each converter.
• Use a universal current-sensitive residual current protective device (RCD, RCM, ELCB or
RCCB), type B, for example, Siemens SIQUENCE RCCB. Connect the RCCB in series with the
overcurrent protective devices.
• Rated residual current is 300 mA.
• The motor cables are maximum 15 m (49 ft) and are shielded. Additional information
about motor cables:
50
WARNING
Maximum permissible cable length (Page 58)
Operating Instructions, 09/2020, FW V4.7 SP13, A5E48681219B
SINAMICS G115D distributed drive