Technical Data
Effective: May 1998
Page
40
TD.44A.01.T.E
Cutler-Hammer
Magnum DS
Metal-Enclosed
Low-Voltage Switchgear
Typical Specification
General — Magnum DS indoor low-
voltage metal-enclosed switchgear
shall consist of a stationary structure
assembly and one or more removable
Magnum DS power circuit breakers
complete with disconnecting devices
and other necessary accessories. The
switchgear shall be suitable for 600
volts maximum service and shall with-
stand a 2200 Vac dielectric test in
accordance with ANSI standards. It
shall be designed, manufactured and
tested in accordance with the latest
applicable standards of IEEE, NEMA,
ANSI, UL and CSA. Documentation
of design testing shall be third-party
certified.
Stationary Structure — Each steel unit
forming part of the stationary assem-
bly shall be a self-contained housing
having one or more individual breaker
or instrument compartments, and a
rear compartment for the buses and
outgoing cable connections.
Prying slots shall be provided on the
base of the structures for ease of posi-
tioning in equipment rooms.
A rigid integral steel base shall be pro-
vided for each section, which will allow
movement of shipping groups directly
on rollers without the need for a sepa-
rate skid.
Each circuit breaker compartment shall
be equipped with primary and second-
ary contacts, drawout extension rails,
stationary levering mechanism parts,
and required instrument current trans-
formers. A formed steel door, sup-
ported on concealed hinges with
removable pins, shall be provided for
each circuit breaker compartment.
Access to the integral circuit breaker
control panel, including the trip unit,
shall be provided without the need to
open the breaker compartment door.
Closed-door spring charging and lever-
ing operations shall also be accom-
plished without the need to open the
breaker compartment door.
The top of the unit shall be enclosed
with removable steel sheets, which
include necessary hooded ventilation
openings. A separate removable
access panel shall be provided for drill-
ing of control conduit hubs. A metal
wireway with removable covers shall
be provided for shipping-split wiring.
Pull-apart type terminal blocks shall
also be provided for rapid, error-free,
shipping split assembly. A metal-
enclosed vertical wireway shall be
provided for routing of field installed
control wiring.
The structure shall be so designed that
future additions may readily be made
at any time. The steel structure shall be
thoroughly cleaned and phosphatized
prior to the application of the ANSI No.
61 finish.
A white, laminated, plastic engraved
circuit designation nameplate shall be
provided on each circuit breaker door.
Buses and Connections — Each
breaker circuit shall include the neces-
sary three-phase copper bus and con-
nections between the source bus and
one set of circuit breaker studs. NEMA
2-hole cable lugs, attached to silver-
plated copper extensions for the out-
going cables, shall be provided on the
other set of circuit breaker studs. The
buses and connections shall consist of
high-conductivity (silver-plated) (tin-
plated) copper bar mounted on heavy-
duty supports, and having bolted
joints. All bolted bus joints shall utilize
Belleville type spring washers to main-
tain maximum joint integrity through
continuous thermal cycling. The bus
system shall be suitable for applica-
tions on power systems requiring a
(100) (150) (200) kA short circuit with-
stand rating without upstream current
limiting fuses.
Terminal blocks with integral-type
barriers shall be provided for circuit
breaker secondary circuits. The termi-
nal blocks shall be front accessible
through a hinged access panel above
each circuit breaker.
All control wiring shall be securely fas-
tened to the switchgear assembly with-
out the use of adhesive wire anchors.
A dedicated wiring path shall be pro-
vided for purchaser’s installed control
wiring. Non-adhesive anchors shall
also be provided for anchoring of pur-
chaser’s installed wiring.
Disconnecting Devices — The station-
ary part of the primary disconnecting
devices for each circuit breaker shall
consist of a set of contacts extending
through a glass polyester insulating
base. Buses and outgoing cable termi-
nals shall be directly connected to
them. The corresponding moving con-
tacts shall consist of a set of contact
fingers suitably spaced on the circuit
breaker studs. For ease of inspection
and maintenance, contact fingers shall
not be a permanent part of the station-
ary structure. In the “connected” posi-
tion, these contacts shall form a
current-carrying bridge. The assembly
shall provide a multitude of silver-to-
silver high-pressure point contacts.
High uniform pressure on each finger
shall be maintained by springs. The
entire assembly shall be full floating
and shall provide ample flexibility
between the stationary and moving
elements. Contact engagement shall
be maintained only in the “connected”
position.
The secondary disconnecting devices
shall consist of floating fingers
mounted on the stationary unit and
automatically engages contacts
located at the front of the compart-
ment. The secondary disconnecting
contacts shall be silver-plated to insure
permanence of contact. Contact
engagement shall be maintained in the
“connected” and “test” positions.
Removable Element — The removable
element shall consist of a Magnum DS
power circuit breaker equipped with
the necessary disconnecting contacts
and interlocks for drawout application.
The removable element shall have
four-position features and shall permit
closing the compartment door with the
breaker in the “connected,” “test,” and
“disconnected” positions.
Power Circuit Breakers — The circuit
breaker shall be Magnum DS, operat-
ing on the De-ion arc interruption prin-
ciple. These breakers shall incorporate
specially designed circuit-interrupting
devices that provide high interrupting
efficiency and minimize the formation
of arc flame and gases.
The primary contacts shall have an
easily accessible wear indicator to indi-
cate main contact erosion. The breaker
closing time shall be no more than
three cycles. Each breaker shall have
three windows in the front cover to
offer clear indication of trip and close
electrical accessories mounted in the
breaker. The breaker shall be equipped
with “De-ion” arc chutes which effec-
tively enclose the arcing contacts and
confine the arc to reduce the distur-
bance caused by short-circuit interrup-
tion. Each breaker shall be equipped
with a position indicator, mechanically
connected to the circuit breaker mech-
anism.
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