Eaton Cutler-Hammer Digitrip RMS 510 Instructions Manual page 19

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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