ABB VD4G-25 Installation And Operating Instructions Manual page 22

V D 4 G I N S TA L L AT I O N A N D O P E R AT I N G I N S T R U C T I O N S
22
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5. Description
19 STU Shunt Test Unit
Device for monitoring functionality and continuity
of shunt opening/closing releases.
Owing to their particular construction, the
functionality of the shunt closing (-MBC) and
opening releases (-MBO1, -MBO2) cannot be tested
with dedicated relays (e.g. TCS Test Control
Supervision, CCC Control Coil Continuity) or with
the REF monitoring and protection unit. The only
device able to test this functionality is the STU
device. Please contact us if this test must be
performed with devices other than STU.
The STU device can be used in conjunction with the
shunt opening release (-MBO1; -MBO2) or shunt
closing release (-MBC) for functionality and
continuity tests.
The Shunt Test Unit for testing/monitoring is used
to test the continuity of releases with rated
operating voltage between 24 V and 250 V (AC and
DC), as well as the functionality of the release's
electronic circuit.
The continuity test is performed cyclically with a
20-second interval between one test and the next.
The unit has optical LED indicators on the front. The
following information is given:
• POWER ON: power is being supplied
• (-MO) TESTING: test is being performed
• TEST FAILED: this signal is given after a test has
failed or when there is no auxiliary power being
supplied
• ALARM: this signal is given after three tests have
failed.
There are two change-over relays on the unit that
allow these two events to be signaled in the remote
mode:
• test failed (resetting occurs automatically once
the alarm has ceased)
• failure of three tests (resetting only occurs by
means of the manual - RESET - on the front of the
unit)
A manual - RESET - key is also installed on the front
of the unit.
Characteristics
Un
Maximum interrupted current
Maximum interrupted voltage
24 ... 250 V A.C./D.C.
6 A
250 V A.C.