![background image](http://html1.mh-extra.com/html/eaton/magnum-pxr/magnum-pxr_technical-product-manual_4157693011.webp)
11
Overview of the Magnum PXR low voltage circuit breaker
MAGNUM PXR PRODUCT GUIDE
PA013006EN September 2022 www.eaton.com
1
Motorized remote racking (MR2)
Eaton’s integral motorized remote racking (MR2) provides
a means of remotely racking any Magnum drawout circuit
breaker. The integral racking system can also be utilized
to open and close the circuit breaker remotely, using
local or remote controls. The addition of an MR2 system
helps mitigate electrical arc flash exposure by allowing the
operator to work from outside the arc flash boundary. For
more information on Eaton’s integral motorized remote
racking (MR2), see the MR2 section in Accessories and
Peripheral Devices.
Construction characteristics
From the inside out, safety is of paramount importance
with special attention given to live parts insulation
and segregation between phases. Careful selection of
materials, meticulous assembly, rigorous testing, and
unsurpassed experience make Magnum a proven reliable
product.
Rigid frame housing
Magnum circuit breakers use a rigid frame housing
construction of durable engineered thermoset composite
resins.
•
Strong and lightweight material with strength to weight
ratio twice that of steel. Proven able to withstand high
dynamic and thermal stresses.
•
Excellent dielectric characteristics, resisting arc tracking.
Three piece construction
The 3-piece construction (rear housing, front housing,
and cover) provides support while isolating and insulating
power conductors.
•
The 2-piece case encloses the current paths and arc
chambers. Chambers act to channel arc gases up and
out during interruption.
•
The operating mechanism and accessories sit on
the front of the case. Only the insulating front cover
needs to be removed to access mechanism and/or
accessories.
•
The operating mechanism achieves a longer life as a
result of reduced frame deflection during operation
along with stiff component mounting.
Two-step stored energy mechanism
Magnum circuit breakers are equipped with a true 2-step
stored energy mechanism.
•
Closing springs can be charged manually or electrically.
•
5 to 7 downward strokes on the charging handle
completes charging process.
•
Mechanism provides for a complete OPEN – CLOSE –
OPEN cycle.
Unsurpassed performance design
The performance characteristics of the Magnum breaker
are attributed in many ways to a C-loop current path
design and movement. Contact fingers perform both the
main and arcing contact functions on different parts of the
same finger. A complete movable contact assembly is a
combination of several single contact fingers. The exact
number of contact fingers required depends upon the
frame size and interrupting rating of the breaker. Braided
connectors (flexible shunts) are used to attach each
contact finger. The result is an efficient and uniquely func-
tional main contact system with the following advantages:
•
Eliminates bolted joints reducing hot spots.
•
Reduced mounting space for primary contacts.
•
Smaller and lighter operating mechanism for longer life.
•
Higher interrupting and short time (withstand) ratings.
•
5-cycle or less closing.
•
Improved contact material.
•
Contact wear indicator for each primary contact
structure.
•
Individually removable arc chambers insulate/isolate
each pole.
•
Ability to withstand high dynamic and thermal stresses.