Technical Data
Effective: May 1998
Page
37
TD.44A.01.T.E
Cutler-Hammer
Magnum DS
Metal-Enclosed
Low-Voltage Switchgear
Features – Breaker
Contacts
The Magnum DS has silver tungsten
moving contacts and silver graphite
stationary contacts. The contacts pro-
vide a long-wearing, low-resistance
joint. The contacts are protected from
arcing damage even after repeated
interruptions by the “heel-toe” action
which causes the integral arcing con-
tacts to mate before the main contacts
part. The arcing contacts then part last,
striking the arc away from the main
contacts.
The main contacts are of the butt type
and are composed of a multiplicity of
fingers to give many points of contact
without alignment being critical.
Magnum DS Breaker Contacts
(Arc Chutes Removed)
Stored-Energy Mechanism
A cam-type closing mechanism closes
the breaker. It receives its energy from
a spring that can be charged by a man-
ual handle on the front of the breaker
or by a universal electric motor.
Release of the stored energy is accom-
plished by manually depressing a
button on the front of the breaker
or electrically energizing a releasing
solenoid.
Arc Chute
There are three basic means of extin-
guishing an arc: lengthening the arc
path; cooling by gas blast or contrac-
tion; deionizing or physically removing
the conduction particles from the arc
path.
The De-ion
T
principle is incorporated
in all Magnum DS circuit breakers. This
makes possible faster arc extinction for
a given contact travel, ensures positive
interruption and minimum contact
burning.
Levering Mechanism
The worm gear levering mechanism is
self-contained on the breaker drawout
element and engages slots in the
breaker compartment. A removable
crank is used to lever the breaker
between the connected, test and dis-
connected positions.
Mechanical interlocking is arranged so
that levering cannot be accomplished
unless the breaker is in the opened
position.
Protection During Levering Operation
When levering the breaker between
the connected, test and disconnected
positions, the operator is protected
from contact with live parts by the
breaker door.
Levering Magnum DS Breaker
True Two-Step Stored Energy Closing
refers to the sequence required to
charge and close the breaker.
1. The breaker closing springs are
charged either through the manual-
charging handle or by the optional
charging motor. The breaker is
mechanically interlocked to prevent
closing of the breaker until the clos-
ing springs are fully charged.
2. With the closing springs fully
charged, the breaker can then be
closed by pressing the manual close
pushbutton on the breaker, or by the
optional spring release coil through
a remote electrical signal.
This means that the energy required to
open the breaker is always prestored
following a closing operation.
“Stored energy” is energy held in wait-
ing, ready to open or close the breaker
within five cycles or less. The unique
cam and spring design provides neces-
sary energy for a single close-open
sequence as well as the energy for
multiple charge-close operations such
as this possible sequence: charge-
close-recharge-open-close-open.
The closing springs are interlocked
with the breaker racking mechanism
to insure the closing springs are dis-
charged before the breaker can be
removed from the compartment.
Manually Operated Breakers — Manu-
ally operated breakers are equipped
with a manual charging handled to
charge the closing springs. Manual
closing and tripping pushbuttons are
utilized to operate the breaker. Remote
closing and tripping can be accom-
plished by installing optional electric
spring release and shunt trip coils (see
Table R5 for available control voltages,
currents and motor-operated spring
charging times). The breaker closing
springs must be charged manually,
then remote closing and tripping sig-
nals can be sent to the breaker.
Electrically Operated Breakers — Elec-
trically operated breakers are equipped
with a spring charging motor and elec-
trically operated spring release and
shunt trip coils (see Table R5 for avail-
able control voltages, currents and
motor-operated spring charging
times). The breaker manual charging
handle can be used to charge the clos-
ing springs when power is not avail-
able to the charging motor.
Provisions for Padlocking — All break-
ers include provision for padlocking
open to prevent electrical or manual
closing. This padlocking can secure the
breaker in the connected, test or dis-
connected position by preventing
levering of the breaker.
Ease of Inspection and Maintenance —
Magnum DS breakers are designed for
maximum accessibility and the utmost
ease of inspection and maintenance.
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