Short Circuit Current Rating of the Control Panel Power Circuit
An industrial control panel must be marked with a so-called SCCR - Short Circuit Current Rating. In the IEC, this approximately corresponds to the Icw value of the switchboard.
The NEC 2008 Art. 409 describes the specifications of short circuit current rating mark on industrial control panels (with reference to the UL 508A, SB4). For short circuit rating, not only the short circuit breaking capacity, e.g. of the circuit breaker, but also the short circuit rating of every individual device in the power circuit is relevant. The SCCR-relevant components in the power circuit include circuit breakers, contactors, overload relays, solid-state switching devices, terminals, busbars, the line side of control transformers and frequency converters, however, no internal wiring of the industrial control panel.
The lowest value is applicable to the entire industrial control panel. No higher short circuit current shall occur on the industrial control panel’s supply terminals.
Standard tables exist at Siemens for motor branches, with standardized devices and wiring from 0.5 HP to 500 HP and SCCR values up to 65 kA.
For more extensive technical documentation, please contact the responsible office in your local region.