32
A DVAC® 3 8 K V I N STA LL ATI ON , OPE R ATI ON A N D M A I NTE N A NCE M A N UA L
—
Accessories
ADVAC® smart coils
Undervoltage release (-MBU)
The undervoltage release opens the circuit breaker
when there is a sensible reduction in or lack of
voltage that powers it. The circuit breaker can only
close when the release is energized (the closing
lock is obtained mechanically). It can be used for
remote release (by means of a push button of the
normally closed type), for locking on automatic
closing/opening in the absence of voltage in the
auxiliary circuits. Supplied by means of the
secondary output of a voltage transformer, it
provides locking upon automatic closing/opening
in the absence of voltage in the medium voltage
main circuit. If shunt closing release -MBC and
undervoltage release -MBU have the same supply
voltage and the circuit breaker must close
automatically when auxiliary voltage returns, there
must be a delay of at least 50 ms between the
undervoltage release energizing and the shunt
closing release energizing to allow the closing
operation to take place.
Undervoltage release mechanical override
This is a mechanical device that allows the
undervoltage release trip to be temporarily
excluded. When the ADVAC circuit breaker
is fitted with an undervoltage release, the
undervoltage release mechanical override
must be used to discharge the breaker prior
to removal from the compartment.
