Siemens SENTRON 3VL System Manual page 42

Functions
5.1 Current protection
The circuit breaker as an overload current tripping system
1. Overcurrent trip unit of the SENTRON VL160X to VL630 circuit breaker, thermomagnetic, TM.
The overcurrent trip unit and short-circuit release work with bimetals and magnetic coils.
They are available with fixed settings or adjustable.
The 4-pole circuit breakers for system protection can be supplied with overcurrent trip units
in all 4 poles or without an overcurrent trip unit in the 4th pole (N). From 100 A, the trip units
in the 4th pole (N) can be set to 60% of the current in the 3 main current paths, so that safe
protection of the neutral conductor can be guaranteed with a reduced cross-section.
The circuit breakers for starter combination applications are usually combined with motor
contactor and suitable overload relays.
The non-automatic circuit breakers have integrated self-protection against short-circuit so
that back-up fuses can be omitted. These circuit breakers have no overload protection.
Four-pole circuit breakers have no short-circuit release in the 4th pole (N).
42
3VL molded-case circuit breakers
System Manual, 03/2009, 110 0110 - 02 DS 01