Siemens SENTRON 3VL System Manual page 22

Product description
3.3 Configuration
Power supply
The protection functions of the electronic overcurrent trip unit are guaranteed without
additional auxiliary voltage. The overcurrent trip units are supplied with energy via internal
current transformers. The protection function is parameterized via rotary encoding switches
on the ETU or via an LCD display. In the case of an LCD display, the electronic overcurrent
trip unit must be activated. This requires a 3-phase (3-pole) load current of at least 20% or,
in the case of a single-phase (single-pole) load, 30% of the relevant rated current of the
circuit breaker. If this load current is not available, the necessary auxiliary energy can be
supplied via a battery power supply (order no. 3VL9000-8AP00). With communication-
capable circuit breakers, the trip unit is supplied with energy via the COM10/COM20 module.
4-pole circuit breakers
The four-pole circuit breakers for system protection can be supplied in all 4 poles with or
without current transformers. The trip units in the 4th pole (N) can be set to 50% or 100% of
the current in the 3 main current paths dependent on the frame size, so that safe protection
of the neutral conductor can be guaranteed even with a reduced cross-section. In the case of
LCD-ETUs, the neutral conductor protection can be adjusted in steps from 50% to 100% or
switched off.
22
3VL molded-case circuit breakers
System Manual, 03/2009, 110 0110 - 02 DS 01