Eaton Cutler-Hammer Digitrip RMS 510 - Page 19

AD 33-855-4
Page
18
9.7
Digitrip
RMS
Direct
Trip Actuator
(DTA)
.
and
Auxiliary
Switch
Kit
(See
Figure
3-6)
The
Digitrip
RMS
Direct
Trip
Actuator
(DTA)
re-
ceives
ln
electrical
trip
pulse
from
the Trip
Unit
via
the
Auxiliary
CT
Module
and
provides
the
mechanical
trip force
to
trip
the Breaker.
The DTA
is
made
up
of a
permanent
magnet,
a
disc
held
by the
magnet,
a
rod
acted
on by
a
spring,
a
means
for tripping
the Breakel
and a
iesei
Mechanism
for mechanically
resetting
the
DTA.
The
magnet
cannot
pull
and
reset
the disc
against
the force
of
the spring
acting
on the
rod,.
bit
it
can overcome
the spring
force
when
the disc
is
in contact
with
the magnet
pole
piece.
A
tripping
pulse from the
Trip
Unit counteracts
the
effect
of
the
permanent
magnet,
allowing
the
sorino
to separate
the
disc
from
the magnet
pole
piece"anO
to actuate
the
DTA.
The DTA
strikes
the
trip
paOdte
and
trips the
Breaker.
As the
Breaker
opens,
the
Breaker
Mechanism
moves
the
DTA
Reset
Mechanism,
which
moves
the disc
to close
the
air
gap
between
it and
the
magnet
pole
piece'
The DTA
is
reset
when
the disc
is
held in
contact
with
the
magnet
pole
piece,
against
the spring
force.
lf the
DTA
does
not reset
properly, the
DTA
will
hold
the Breaker
in the
trip
free condition
and
the Breaker
will not
be
able
to close'
For
Powered
Trip Units:
Once
an
overcurrent
has
occurred,
the
Trip Unit
sends
an electrical
signal
to the
DTA
which
will
be monitored
until
the
Trip
Unit
is
reset,
keeping
the
Breaker
in a trip
free
condition.
RMS
810
& 910
Retrofit
Kits
include an
Auxiliary
Switch
Kit,
which
usually
mounts
on or
near
the
DTA.
The
Auxiliary
Switch
Kit consists
of a
microswitch
with
mounting
hardware
and
brackets'
The
switch
is used
to
provide
the Trip
Unit
with
information
on
the Breaker
status,
i.e.:
open
or
closed.
This status
information
is
passed
on
through
the
PowerNet
network
HORIZONTAL
TRIP
UNIT
"LTM
ACTIVE"
"LTM
INACTIVE"
VERTICAL
TRIP
UNIT
LTM JUMPER
STANDARD
FROM
FACTORY
"LTM
ACTIVE"
"LTM
INACTIVE"
(c)
(A)
@@@
o ,.--. o
@(J
@,-@
oo@
@
r-.-
O
o\-,,'
@,-@
(B)
Fig.
3-5
Disabling
the
Long
Time
Memory
(LTM)
Function
ElT.il
Efiective
9/01