Accessories
4.10 MMB300 maintenance mode box
3VA molded case circuit breakers with UL and IEC certification
Manual, 01/2019, L1V30435333-01
351
MMB300 maintenance mode box
4.10.1
Operating principle of the MMB300 maintenance mode box
The 3VA6 molded case circuit breakers with the electronic trip system ETUs 3-series,
5-series and 8-series can be functionally expanded with an MMB300
.
With the MMB300 maintenance mode box, the Dynamic Arc Sentry mode (DAS mode,
chapter Arc energy reduction (Page 81)) of the molded case circuit breaker is activated and
the setting parameters for the instantaneous short circuit current I
i
and the ground-fault
current I
g
are set to the lowest setting values of the circuit breaker. This reduces the let-
through energy of the molded case circuit breaker under fault conditions. This results in
improved protection when personnel is in the vicinity of the installation and the installation is
in maintenance mode.
This parameter changeover can occur, for example, through a door contact at the
switchboard or an externally actuated switch. In addition, a signal lamp or horn, for example,
signals when the circuit breaker is in maintenance mode.
A series connection of up to eight 3VA6 molded case circuit breakers with the associated
MMB300 maintenance mode box is possible.
LED display DI Digital input
<SET> button DO Digital output
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