Siemens Sentron 3VA User Manual

Applications
3.4 Use of 3VA UL molded case circuit breaker in DC systems
3VA molded case circuit breakers with UL and IEC certification
Manual, 01/2019, L1V30435333-01
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3.4
Use of 3VA UL molded case circuit breaker in DC systems
3.4.1
Introduction
The main applications for 3VA circuit breakers in DC installations or systems are:
● Public transport systems, e.g. electric cars, underground rail networks and streetcars
● UPS systems
● Photovoltaic systems
● Wind power systems
The 3VA5 molded case circuit breakers for line protection with thermal overload and
magnetic short-circuit releases are suitable for use in DC systems.
Features specific to direct current
Short-circuits are interrupted in DC networks by a method similar to the one applied to high
alternating currents, i.e. by current limiting. A high arc voltage builds up in molded case
circuit breakers, which forces the current to zero when the source voltage (supply system
voltage) is exceeded.
Overloads are interrupted by a completely different principle to the method applied in AC
networks. With direct currents, there is no periodic zero crossing and thus also no period of
time without magnetic energy in the circuit during which the conditions for extinguishing the
arc are favorable. The arc is not extinguished until the arc voltage exceeds the line voltage
and the current reduces to zero. In other words, a high arc voltage must be developed in
order to interrupt the direct current.
The rated operational current values are generally the same for DC and AC applications.
With DC applications, the breaking capacity depends only on:
● The arc extinction method used
● The line voltage

Siemens Sentron 3VA Specifications

General

Brand	Siemens
Model	Sentron 3VA
Category	Circuit breakers
Language	English