Description
2.7 Electronic trip unit
3VA molded case circuit breakers with UL and IEC certification
Manual, 01/2019, L1V30435333-01
81
2.7.2
Connections
The connections on the ETU are illustrated in the diagram below:
①
Interface for an external current transformer for N conductor
②
Interface for connection of an EFB300 external function box and MMB300 maintenance mode
box
③
Connection for test devices TD300 and TD500
2.7.3
Arc energy reduction
The U.S. "National Electrical Code (NFPA 70) Section 240.87" requires special protection
measures for circuit breakers where the highest continuous current setting is rated or can be
adjusted to 1200 A or higher.
The intent of these protection functions is to reduce the let-through energy under fault
conditions (e.g. short-circuit) to the smallest possible amount in order to best protect the
worker.
One method to satisfy this requirement is to provide energy-reducing maintenance switching
with local status indicator.
The Siemens DAS when used with a remote external switch meets this requirement.
3VA6 molded case circuit breakers and Dynamic Arc Sentry
All 3VA6 molded case circuit breakers are equipped with the Dynamic Arc Sentry mode
(DAS mode).
When the 3VA6 molded case circuit breakers are in Dynamic Arc Sentry mode, the
instantaneous short-circuit current I
i
is automatically reduced to the smallest available value
(factory setting). Likewise, the ground-fault current I
g
is reduced to the smallest available
value for the ETU variants with ground-fault protection or ground-fault detection. In this way it
is ensured that the molded case circuit breaker disconnects as quickly as possible under
fault conditions and enhanced personal protection is achieved.
To facilitate optimal adjustment of the molded case circuit breaker in DAS mode to local or
system-specific circumstances, it is possible to configure the DAS parameter set (I
i
and I
g
)
using the powerconfig
parameterization software.
