Eaton Magnum Air MWN-408 User manual

Double-wide Fixed
Standard Frame Fixed
User Manual Magnum
1812.900A
Magnum LV-Air Circuit Breaker
Narrow Frame Fixed

Magnum
1812.900A 2
Work on medium and low voltage switchgear installations, such as setting up,
the connecting of cables, operation, inspection and maintenance must only be
carried out by persons authorised to do so.
Administrative data
Version number: A
Date of issue: 01-03-2005
Source file: IB.2C13060H03 eff. 7/02

Magnum
1812.900A 3
CONTENTS
1INTRODUCTION ....................................................................................................................................................... 5
1.1 General information ..............................................................................................................................5
1.2 Purpose ..........................................................................................................................................6
1.3 Safety features .....................................................................................................................................6
1.4 Safe practices .......................................................................................................................................8
1.5 Qualified personnel...............................................................................................................................8
1.6 Other publications and documentation.................................................................................................8
2RECEIVING, HANDLING AND INSTALLATION........................................................................................................ 9
2.1 General information ..............................................................................................................................9
2.2 Suggested tools....................................................................................................................................9
2.3 Unpacking circuit breaker .....................................................................................................................9
2.3.1 Storing circuit breaker......................................................................................................................9
2.4 Lifting circuit breaker ..........................................................................................................................10
2.5 Circuit breaker inspection ...................................................................................................................10
2.6 Adapting cassette...............................................................................................................................11
2.6.1 Rejection interlocks .......................................................................................................................11
2.6.2 Installing secondary jumpers .........................................................................................................12
2.7 Installing drawout circuit breaker........................................................................................................12
2.7.1 Circuit breaker positioning .............................................................................................................12
2.7.2 levering circuit breaker...................................................................................................................14
2.8 Fixed circuit breaker ...........................................................................................................................15
2.9 Circuit breaker operation ....................................................................................................................15
3CIRCUIT BREAKER DESCRIPTION AND OPERATION .......................................................................................... 16
3.1 Introduction ........................................................................................................................................16
3.2 Basic circuit breaker assembly ...........................................................................................................20
3.3 Pole units............................................................................................................................................20
3.3.1 Primary moving contacts ...............................................................................................................20
3.3.2 Primary stationary contacts............................................................................................................21
3.4 Operating mechanism ........................................................................................................................22
3.4.1 Manual operation ...........................................................................................................................22
3.4.2 Electrical operation ........................................................................................................................23
3.4.3 Anti-pump feature..........................................................................................................................23
3.5 Arc chambers .....................................................................................................................................23
3.5.1 Arc chute .......................................................................................................................................23
3.6 Electronic tripping system ..................................................................................................................24
3.6.1 Microprocessor-based trip unit ......................................................................................................24
3.6.2 Rating plug.....................................................................................................................................26
3.6.3 Current sensors .............................................................................................................................26
3.6.4 Trip actuator...................................................................................................................................27
3.6.5 Mechanical trip flag........................................................................................................................27
3.6.6 Making current release ..................................................................................................................27
3.6.7 High instantaneous trip option .......................................................................................................28
3.6.8 Voltage taps ...................................................................................................................................28
3.7 Secondary contacts and connection diagrams....................................................................................28
3.7.1 Connection diagrams .....................................................................................................................29
3.8 Accessory devices..............................................................................................................................36
3.8.1 Plug-in electrical accessories .........................................................................................................36
3.8.2 Internal electrical accessories ........................................................................................................38
3.8.3 Mechanical accessories.................................................................................................................40
4DRAWOUT CIRCUIT BREAKER AND CASSETTE.................................................................................................. 43
4.1 General ...............................................................................................................................................43
4.2 Drawout cassette ...............................................................................................................................43
4.3 Drawout circuit breaker dimensions ...................................................................................................43
4.4 Drawout cassette dimensions ............................................................................................................43
5FIXED CIRCUIT BREAKER...................................................................................................................................... 45
5.1 General ...............................................................................................................................................45
5.2 Fixed circuit breaker dimensions ........................................................................................................45

Magnum
41812.900A
6INSPECTION AND MAINTENANCE .......................................................................................................................46
6.1 General ...............................................................................................................................................46
6.2 General cleaning recommendations ...................................................................................................46
6.3 When to inspect .................................................................................................................................46
6.4 What to inspect ..................................................................................................................................47
6.4.1 Functional field testing ...................................................................................................................47
6.4.2 Arc chute inspection ......................................................................................................................48
6.4.3 Primary contact inspection.............................................................................................................49
6.5 Circuit breaker modifications and changes .........................................................................................50
6.5.1 Rating plug replacement ................................................................................................................50
6.5.2 Current sensor replacement ..........................................................................................................51
7TROUBLESHOOTING.............................................................................................................................................. 53
7.1 Introduction.........................................................................................................................................53
8RENEWAL PARTS...................................................................................................................................................55
8.1 General ...............................................................................................................................................55

Magnum
1812.900A 5
1 INTRODUCTION
1.1 General information
The Magnum Air Circuit Breaker is a fixed or drawout air
circuit breaker design utilizing an electronic tripping
system. It is designed and tested for use at nominal
voltages of 380-440 and 500-690 volts ac. Magnum
circuit breakers are available in three physical frame sizes
with continuous current ratings from 800 through 6300 A.
and interrupting capacities from 42 kA to 150 kA.
The three physical frame sizes have common height and
depth dimensions, differing only in width (Figure 1-1).
The circuit breaker nameplate provides complete rating
information. All Magnum circuit breakers are 100
percent rated, and are built and tested in an ISO 9002
certified facility to applicable IEC and BS standards
(Table 1-1, Figure 1-2 and Figure1-3). In addition, the
Magnum circuit breaker carries a full third party KEMA
certification for both short circuit and endurance test
requirements.
Magnum circuit breakers use a rigid frame housing of
engineered thermoset composite resins which has high
strength structural properties, excellent dielectric
characteristics and arc tracking resistance.
The drawout Magnum circuit breaker is a through-the-
door design having three breaker positions with the
compartment door closed (CONNECT, TEST,
DISCONNECT) and one position out of its compartment
on extension rails (REMOVE). The operating mechanism
is a two-step stored energy mechanism, either manually
or electrically operated.
When withdrawn on captive compartment cassette
extension rails, Magnum circuit breakers can be
inspected, accessory items added, and minor
maintenance performed. The inside of the compartment
can also be inspected with the circuit breaker on its
extension rails.
NOTICE!
PLEASE READ AND UNDERSTAND THESE
INSTRUCTIONS BEFORE ATTEMPTING TO UNPACK,
INSTALL, OPERATE OR MAINTAIN THIS
EQUIPMENT. STUDY THE BREAKER AND ITS
MECHANISM CAREFULLY BEFORE ATTEMPTING
TO OPERATE IT ON AN ENERGIZED CIRCUIT.
Double-wide Fixed Narrow Frame Fixed
Standard Frame Fixed
Figure 1-1: Family of Magnum Low Voltage Air Fixed and Drawout Circuit Breakers (800-6300 Amperes)

Magnum
61812.900A
WARNING
MAGNUM CIRCUIT BREAKERS SHOULD NOT
UNDER ANY CIRCUMSTANCES BE APPLIED
OUTSIDE THEIR NAMEPLATE RATINGS.
OPERATION OUTSIDE OF THESE RATINGS COULD
RESULT IN DEATH, BODILY INJURY OR PROPERTY
DAMAGE.
1.2 Purpose .
This instruction manual is expressly intended to cover the
installation, operation and maintenance of Magnum Air
Circuit Breakers. These circuit breakers may be supplied
as part of complete switchboard assemblies or as
separate components. This manual applies only to the
circuit breaker and (if drawout) it’s mating cassette.
Magnum circuit breakers may also be supplied as fixed
mounted devices. In the case of fixed versions of
Magnum circuit breakers, certain sections of this manual,
referring to such items as position interlocks and the
drawout mechanism, will not apply.
Trip units associated with Magnum Air Circuit Breakers
will be addressed in a general manner in this manual.
Specific trip unit details and time-current characteristic
curves are covered in separate documents specific to the
trip units.
Magnum circuit breaker accessory items are discussed
briefly in this manual. Field installation instructions for
such items, however, are covered in individual instruction
leaflets specific to the accessory. This information is also
available from the Eaton website at
www.eatonelectrical.com
For application information, consult Eaton or see
applicable Product Guides, Technical Documents,
Application Publications and/or Industry Standards.
SAFETY
All safety codes, safety standards and/or regulations must
be strictly observed in the installation, operation and
maintenance of this equipment.
WARNING
THE WARNINGS AND CAUTIONS INCLUDED AS
PART OF THE PROCEDURAL STEPS IN THIS
MANUAL ARE FOR PERSONNEL SAFETY AND
PROTECTION OF EQUIPMENT FROM DAMAGE. AN
EXAMPLE OF A TYPICAL WARNING LABEL
HEADING IS SHOWN ABOVE TO FAMILIARIZE
PERSONNEL WITH THE STYLE OF PRESENTATION.
THIS WILL HELP TO INSURE THAT PERSONNEL
ARE ALERT TO WARNINGS. IN ADDITION,
CAUTIONS ARE ALL UPPER CASE AND BOLDFACE.
1.3 Safety features
Magnum circuit breakers and associated drawout
equipment are manufactured with built-in interlocks and
safety related features. They are provided to reduce
hazards to operating personnel and provide proper
operating sequences.

Magnum
1812.900A 7
Table 1-1: Magnum Circuit Breaker Ratings
Maximum
Amperes
Breaker Designation Ics = Icu *
(kA)
Icw1s/3s (kA)
800 MWN-408
MWN-508
MWN-608
MWI-408
MWI-608
MWI-808
MWI-C08
40
50
65
40
65
85
1001
40/NA
50/NA
65/40
40/NA
65/50
85/65
85/65
1250 MWN-412
MWN-512
MWN-612
MWI-412
MWI-612
MWI-812
MWI-C12
40
50
65
40
65
85
1001
40/NA
50/NA
65/40
40/NA
65/50
85/65
85/65
1600 MWN-516
MWN-616
MWI-616
MWI-816
MWI-C16
50
65
65
85
1001
50/NA
65/40
65/50
85/65
85/65
2000 MWN-520
MWN-620
MWI-620
MWI-820
MWI-C20
50
65
65
85
1001
50/30
65/40
65/50
85/65
85/65
2500 MWI-625
MWI-825
MWI-C25
65
85
1001
65/50
85/65
85/65
3200 MWI-632
MWI-832
MWI-C32
MWK-232
65
85
1001
25
65/50
85/65
100/65
NA
4000 MWI-641 3
MWI-841 3
MWI-C413
MWI-640, 64N
MWI-840, 84N
MWI-C40, C4N
MWI-E40, E4N
65
85
1001
65
85
100
1502
65/NA
85/65
100/85
150/100
5000 MWI-850, 85N
MWI-C50, C5N
MWI-E50, E5N
85
100
1502
85/65
100/85
150/100
6300 MWI-863, 86N
MWI-C63, C6N
MWI-E63, E6N
85
100
1502
85/65
100/85
150/100
* All ratings at 690 Vac except MWK which is rated
1100 Vac
1Icu only; Ics = 85kA
2Icu only; Ics = 100kA
3Standard width breaker (not double-wide)
A
B
C
D
E
A. Low voltage air circuit breaker family name
B. Breaker family designation number
C. Breaker frame size in amperes
D. Interrupting capacity rating
E. Factory Equipped Accessories
Figure 1-2: Typical Magnum Nameplate
WARNING
TYPE MAGNUM CIRCUIT BREAKERS ARE ROBUST
AND ARE PROVIDED WITH SAFETY FEATURES.
NEVERTHELESS, THE VOLTAGES, CURRENTS AND
POWER LEVELS AVAILABLE IN AND AROUND THIS
EQUIPMENT WHEN IT IS IN OPERATION ARE
EXTREMELY DANGEROUS AND COULD BE FATAL.
UNDER NO CIRCUMSTANCES SHOULD INTERLOCKS
AND OTHER SAFETY FEATURES BE MADE
INOPERATIVE, AS THIS MAY RESULT IN DEATH,
BODILY INJURY OR PROPERTY DAMAGE.

Magnum
81812.900A
1.4 Safe practices
To protect personnel associated with the installation,
operation and maintenance of this equipment, the
following practices must be followed:
1. Only qualified electrical personnel familiar with
the equipment, its operation and the associated
hazards should be permitted to work on the
equipment. Additionally, only qualified personnel
should be permitted to install or operate the
equipment.
2. Always be certain that the primary and secondary
circuits are de-energized or the circuit breaker is
removed to a safe work location before
attempting any maintenance.
3. For maximum safety, only insert a completely
assembled breaker into an energized cell.
4. Always ensure that drawout circuit breakers are
in one of their designed cell positions, such as
Connect, Test, Disconnect or Remove. A circuit
breaker permitted to remain in an intermediate
position could result in control circuits being
improperly connected resulting in electrical
failures.
1.5 Qualified personnel
For the purpose of operating and maintaining low voltage
power circuit breakers, a person should not be considered
qualified if the individual is not thoroughly trained in the
operation of the circuit breaker and how it interfaces with
the assembly in which it is used. In addition, the individual
should have knowledge of the connected loads.
For the purpose of installing and inspecting circuit
breakers and their associated assembly, a qualified
person should also be trained with respect to the hazards
inherent to working with electricity and the proper way to
perform such work. The individual should be able to de-
energize, clear and tag circuits in accordance with
established safety practices.
1.6 Other publications and documentation
In addition to this instruction manual, other printed
information and documentation is available and supplied
as appropriate. This additional information can include, but
not necessarily be limited to, an instruction manual for a
specific electronic trip unit, instruction leaflets for
accessory items, renewal parts information, necessary
dimensional drawings and a Product (application) Guide.
MWI C32
Circuit Breaker Type
Interrupting
Capacity Frame Size
MWI - Standard and/or Double-
wide Frames
MWN - Narrow Frame
MWK - High Voltage (1100Vac )
Frame
2 - 25,000
4 - 40,000
5 - 50,000
6 - 65,000
8 - 85,000
C - 100,000
E - 150,000
08 - 800 Amps
12 - 1250 Amps
16 - 1600 Amps
20 - 2000 Amps
25 - 2500 Amps
32 - 3200 Amps
40, 41, 4N - 4000 Amps
50 , 5N - 5000 Amps
63, 6N - 6300 Amps
Figure1-3: Magnum Designation Example

Magnum
1812.900A 9
2 RECEIVING, HANDLING AND
INSTALLATION
2.1 General information
Magnum Air Circuit Breakers, when supplied as part of an
assembly, may be shipped already installed in their
respective breaker compartments. Receiving and handling
of this equipment is addressed in an assembly instruction
manual supplied with the assembled equipment. This
instruction manual applies to only the circuit breakers.
2.2 Suggested tools
A large number of different tools are not required to
properly install and maintain Magnum circuit breakers.
The following tools are, however, suggested:
• Flat blade screwdriver
• Phillips head screwdriver
• 3/8” socket (rachet) wrench
• 10 mm socket
• 17 mm socket
• Secondary wiring removal tool
2.3 Unpacking circuit breaker
Before beginning to unpack new Magnum circuit
breakers, read and understand these directions. Following
the directions will ensure that no damage is caused.
Shipping containers should be inspected for obvious signs
of rough handling and/or external damage incurred during
the transportation phase. Record any observed damage
for reporting to the transportation carrier and Eaton, once
the inspection is completed. All reports and claims should
be as specific as possible and include the order number
and other applicable nameplate information.
Every effort is made to ensure that Magnum circuit
breakers arrive at their destination undamaged and ready
for installation. Care should be exercised, however, to
protect the breakers from impact at all times. Do not
remove protective packaging until the breakers are ready
for inspection, testing and/or installation.
When ready to inspect and install the Magnum circuit
breaker, carefully remove the banding straps and lift off
the cardboard box. Remove any additional packing
material and internally packed documentation. The circuit
breaker and/or cassette are mounted to a wooden
shipping pallet.
On drawout circuit breakers shipped without a cassette,
two shipping clamps hook into the breaker side plates
and are held to the pallet with 4 lag screws (Figure 2-1).
Remove the lag screws and clamps. Save the screws and
clamps for future shipment of the breaker. On empty
cassettes, remove the 4 or 5 lag screws and/or machine
screws which pass through the floorpan of the cassette
holding it to the wooden pallet. On drawout breakers
shipped in a cassette, first remove the breaker from the
cassette using the levering mechanism and drawout rails.
After the breaker is removed the machine
screws passing through the floorpan can be removed. On
fixed breakers, remove the lag screws passing through
the mounting feet which hold the breaker to the pallet.
Figure 2-1: Shipping Clamps for Drawout Circuit Breaker
1. Shipping Clamp
Circuit breakers are designed to be easily lifted from the
wooden pallet using an appropriate lifting yoke and
overhead or portable lifting device.
2.3.1 Storing circuit breaker
If it is necessary to store a circuit breaker before
installation, do so in its original shipping container. Keep
the circuit breaker in a clean dry place. Ensure there is
ample air circulation and heat, if necessary, to prevent
condensation. It is very important that the circuit breaker
not be exposed to dirt or moisture.
NOTICE
A CIRCUIT BREAKER THAT HAS BEEN STORED FOR
ANY LENGTH OF TIME SHOULD BE OPERATED A
MINIMUM OF FIVE TIMES BEFORE IT IS PLACED IN
SERVICE.
1

Magnum
10 1812.900A
2.4 Lifting circuit breaker
CAUTION
DO NOT ATTEMPT TO LIFT CIRCUIT BREAKERS
WITH ORDINARY CRANE HOOKS, ROPES, CHAINS
OR OTHER SUCH DEVICES. FAILURE TO FOLLOW
THIS CAUTION COULD RESULT IN DAMAGE TO
VITAL PARTS SUCH AS ARC CHUTES, BARRIERS
AND WIRING OR THE ENTIRE CIRCUIT BREAKER.
To closely examine, install or just become more familiar
with the circuit breaker, carefully lift and place the circuit
breaker on a solid work surface capable of handling the
circuit breaker’s weight (
Table 2-1) or on the captive drawout extension rails of the
breaker compartment. This is accomplished by using the
appropriate lifting yoke and lifter. The lifting yoke consists
of two steel hooks specially shaped to hook under the
integral molded lifting handles on both sides of the circuit
breaker (Figure 3-1). Every effort should be made during
lifting to minimize circuit breaker swing and tilt.
If the circuit breaker is to be lifted onto compartment
extension rails, follow the instructions in paragraph 2.7
entitled “Installing Drawout Circuit Breaker.”
2.5 Circuit breaker inspection
All circuit breakers, once removed from their shipping
containers, should be visually inspected for any obvious
damage.
The current rating of the rating plug installed in the trip
unit should match the current rating of the sensors
mounted on the lower primary stabs of the circuit
breaker. Check to make sure that this match exists. The
rating plug rating can be viewed from the front of the
circuit breaker (Figure 3-4). The sensor rating can be
viewed through the viewing windows at the rear of the
circuit breaker (Figure 2-2). Sensors and rating plugs can
be easily changed as described in Section 6.
Table 2-1: Basic Circuit Breaker Weights
Weights (kg)
Fixed Drawout Universal
cassette
Breaker
model
3P 4P 3P 4P 3P 4P
MWN-408
MWN-412
48 59 48 61 29 32
MWN-508
MWN-512
MWN-516
MWN-520
49 61 48 61 29 32
MWN-608
MWN-612
MWN-616
MWN-620
50 62 48 61 29 32
MWI-408 48 59 56 69 31 36
MWI-412
MWI-608
MWI-612
MWI-616
50 62 59 74 31 36
MWI-620
MWI-808
MWI-812
MWI-816
MWI-820
MWI-C08
MWI-C12
MWI-C16
MWI-C20
51 63 63 79 31 36
MWI-625
MWI-630
MWI-632
MWI-825
MWI-830
MWI-832
MWI-C25
MWI-C30
MWI-C32
MWK-232
58 73 70 88 38 45
MWI-641
MWI-841
MWI-C41
NOT YET AVAILABLE
MWI-640, 64N
MWI-840, 84N
MWI-C40, C4N
MWI-E40, E4N
94 118 116 148 49 65
MWI-850, 85N
MWI-C50, C5N
MWI-E50, E5N
MWI-863, 86N
MWI-C63, C6N
MWIE63, E6N
108 137 131 167 63 79

Magnum
1812.900A 11
2.6 Adapting cassette
Drawout circuit breaker cassettes are built and shipped in
a “basic” configuration that can be adapted in the field to
mate with specific circuit breakers. Specifically, the
rejection interlock must be configured to the specific
circuit breaker to be mated with the cassette, and the
automatic secondary connections may have to be
installed or upgraded. These operations are described in
the following sections.
2.6.1 Rejection interlocks
Within any one physical frame size Magnum drawout
circuit breakers come in a variety of continuous current
and interruption ratings, some of which are incompatible
with others. Double wide circuit breakers also come with
several phase sequence options which are also
incompatible. To prevent the insertion of circuit breakers
with (1) inadequate interrupting capability, (2) with
physically incompatible primary disconnects or (3) with an
incompatible phase sequence, rejection interlock key
plates are provided on both the circuit breaker and
cassette. The key plate on the circuit breaker is pre-
assembled at the factory; but the cassette-side rejection
plate and key pattern must be assembled and installed by
the switchboard builder.
Figure 2-2: Rear View Showing Current Sensor Rating
Through Viewing Window
CAUTION
DO NOT DISABLE REJECTION INTERLOCKS.
DOING SO AND USING A LOWER CAPACITY
CIRCUIT BREAKER IN AN INCOMPATIBLE
CASSETTE COULD RESULT IN AN ELECTRICAL
FAULT WHICH COULD RESULT IN DEATH, BODILY
INJURY AND/OR EQUIPMENT DAMAGE.
The rejection interlocks are steel pins in the floor of the
circuit breaker cassette. As the circuit breaker is pushed
into the structure, the mating pins on the bottom of the
circuit breaker move past a set of corresponding pins in
the cassette, if the circuit breaker and cassette are
compatible. If the circuit breaker and the cassette are
mismatched, the rejection pins will block the insertion of
the circuit breaker into the cassette before the levering-in
mechanism is engaged.
Before attempting to push the circuit breaker into the
DISCONNECT position, compare the positioning of
rejection interlock pins in the cassette with Table 2-2 and
Figure 2-4 and the information supplied on the circuit
breaker’s nameplate. Proceed if the circuit breaker and
cassette are compatible.
Figure 2-3: One Side of Drawout Circuit Breaker Properly
Seated on Extension Rail
1. Molded Rail Supports
2. Extension Rail Cutout
1
2

Magnum
12 1812.900A
2.6.2 Installing secondary jumpers
On drawout circuit breakers the automatic secondary
connector between the circuit breaker and cassette can
be ordered either fully populated or depopulated (without
terminal blocks and jumper wires installed); these parts
can be ordered separately and installed by the customer.
These kits can also be used to add additional secondary
wiring to upgrade circuit breakers in the field.
2.7 Installing drawout circuit breaker
In structures equipped for drawout circuit breakers, a
bolted-in cassette with movable extension rails supports
the circuit breaker. The extension rails must first be pulled
all the way out. Once the rails are fully extended, the
circuit breaker can be carefully placed on the extension
rails.
CAUTION
IT IS IMPORTANT TO TAKE GREAT CARE WHEN
PLACING A DRAWOUT CIRCUIT BREAKER ON ITS
EXTENSION RAILS. IF THE CIRCUIT BREAKER IS
NOT PROPERLY SEATED ON THE EXTENSION
RAILS, IT COULD FALL FROM THE RAILS CAUSING
EQUIPMENT DAMAGE AND/OR BODILY INJURY.
Carefully lower the circuit breaker down onto the
extension rails. Be certain that the circuit breaker’s four
molded drawout rail supports are fully seated in the
extension rail cutouts on both sides (Figure 2-3). Do not
remove the lifting yoke from the circuit breaker until it
is properly seated on the rails.
Once the circuit breaker is on the extension rails and the
lifting yoke is removed, proceed with the rest of the
circuit breaker installation.
From Table 2-2, make a pin location comparison. Stop
nuts should be torqued to 8-10 Ft.-Lb.
Figure 2-4: Cassette Rejection Interlock Pin
Positioning/Installation
Table 2-2: Rejection Interlock Pin Locations
2.7.1 Circuit breaker positioning
The Magnum drawout circuit breaker has four normal
positions:
• REMOVE (Withdrawn) (Figure 2-5)
• DISCONNECT (Figure 2-6)
• TEST (Figure 2-7)
• CONNECT (Figure 2-8)
The REMOVE position is a position outside the
compartment on the cassette’s drawout rails where the
circuit breaker is not engaged with the levering
mechanism. The DISCONNECT, TEST, and CONNECT,
positions are reached by means of the levering
mechanism.
With the breaker solidly positioned on the cassette’s
extension rails and levering-in mechanism in the
DISCONNECT position, carefully and firmly push the
circuit breaker into the compartment as far as it will go.
The outer (recessed) portion of the circuit breaker face
plate should align with the GREEN target line (labelled
DISC) on the inside top left wall of the cassette
(Figure 2-9).
Pin Locations
Cell for 1 2 3 4 5 6 7 8
MWN-408, 412 x x
MWN-508, 512, 516, 520 x x x
MWN-608, 612, 616, 620 x x x x
MWI-608, 612, 616, 620 x x x x
MWI-808, 812, 816, 820 x x x x x
MWI-C08, C12, C16, C20 x x x x x x
MWI-625, 632 x x x x
MWI-825, 832 x x x x x
MWI-C25, C32 x x x x x x
MWI-640 x x x
MWI-64N x x x
MWI-840 x x x
MWI-84N x x x
MWI-C40 x x x x
MWI-C4N x x x x
MWI-E40 x x x x x
MWI-E4N x x x x x
MWI-850, 863 x x x
MWI-85N, 86N x x x
MWI-C50, C63 x x x x
MWI-C5N, C6N x x x x
MWI-E50, E63 x x x x x
MWI-E5N, E6N x x x x x
MWK-225, 232 x x x x x

Magnum
1812.900A 13
• No Electrical Connections Made
• Breaker On Extension Rails
• Remove or Inspection Position
Figure 2-5: Remove Position
• Only Ground Connection Made
• Breaker Still Behind Door
• Typical Storage Position
Figure 2-6: Disconnect Position
• Breaker and Trip Unit Testing
• Primary Connection Not Made
• Secondary and Ground Connections Made
Figure 2-7: Test Position

Magnum
14 1812.900A
• Full Breaker Operation
• Primary, Secondary and Ground Connections Made
• Fully Racked into Cassette (Compartment)
Figure 2-8: Connect Position
CAUTION
MAKE CERTAIN THAT THE CIRCUIT BREAKER IS
FULLY INSERTED INTO ITS COMPARTMENT BEFORE
ANY ATTEMPT IS MADE TO LEVER THE CIRCUIT
BREAKER. ATTEMPTING TO LEVER THE CIRCUIT
BREAKER IN BEFORE IT IS FULLY POSITIONED
INSIDE ITS COMPARTMENT CAN RESULT IN
DAMAGE TO BOTH THE CIRCUIT BREAKER AND THE
COMPARTMENT.
Figure 2-9: Cassette Label Showing Disconnected, Test and
Connected Position of Recessed Cover
2.7.2 levering circuit breaker
The circuit breaker is now ready to be levered. With the
circuit breaker OPEN, the levering device access door can
be raised. The levering device is hand operated using a
standard 3/8” square drive and ratchet, which is not
provided (Figure 2-10). As long as the levering access
door is raised, the circuit breaker is held trip free. Begin
by rotating the levering-in screw to the full
counterclockwise (DISCONNECT) position.
Close the compartment door and begin levering the
breaker into its different positions using a clockwise
ratcheting motion. The circuit breaker can be levered
with the compartment door open or closed, but it is
advisable to close the door prior to levering.
The position of the circuit breaker within its compartment
is indicated by color coded position indicators (Red =
Connect, Yellow = Test, Green = Disconnect)
(Figure 2-10). When the circuit breaker is levered fully to
the DISCONNECT or CONNECT position the levering
shaft hits a hard stop; do not exceed 34.2 N.m. of torque
or the levering mechanism may be damaged. To remove
the circuit breaker from its compartment, follow the
procedure just described using a counterclockwise
ratcheting motion.
NOTICE
THE CIRCUIT BREAKER MECHANISM IS
INTERLOCKED SUCH THAT CHARGED CLOSING
SPRINGS ARE AUTOMATICALLY DISCHARGED IF
THE CIRCUIT BREAKER IS LEVERED INTO OR OUT
OF THE CELL. DISCHARGE TAKES PLACE
BETWEEN THE DISCONNECT AND TEST POSITION.

Magnum
1812.900A 15
Figure 2-10: Levering Position Indication
2.8 Fixed circuit breaker
The Magnum fixed type circuit breaker differs from the
drawout version in that it has no levering device, primary
disconnects and secondary disconnects (Figure 2-11). In
addition, a fixed circuit breaker does not have a standard
feature to hold the breaker in a trip-free position. Fixed
circuit breakers can be mechanically interlocked using
either the optional key interlock (which is mounted
through the front panel) or with optional cable interlocks
which operate on the tripper bar (Figure 3-1).
Circuit breaker terminals have holes for making bolted
horizontal primary bus connections. Adapters are
available for making vertical primary bus connections.
Secondary connections can be made through standard
terminal blocks or a special connector compatible with
the drawout circuit breaker’s type secondary connector.
Both secondary connection devices are mounted at the
top front of the circuit breaker.
The fixed circuit breaker frame has two mounting feet,
one on each side, to permit the fixed circuit breaker to be
securely mounted. Each mounting foot has two slotted
mounting holes which are used to bolt the circuit breaker
securely in place. Use either M10 or 3/8” bolts for this
purpose. Refer to the dimensional drawings refered to in
Section 5 (Fixed Circuit Breakers) for circuit breaker and
bus stab dimensions.
Figure 2-11: Typical Fixed Magnum Circuit Breaker
1. Mounting Foot
NOTICE
REFER TO THE CIRCUIT BREAKER WEIGHTS IN
TABLE 2-1 TO ENSURE THAT THE PANEL ON
WHICH A FIXED CIRCUIT BREAKER IS TO BE
MOUNTED IS CAPABLE OF SUPPORTING THE
WEIGHT.
2.9 Circuit breaker operation
Circuit breakers should be operated manually and/or
electrically before they are put into service. This can be
done during the installation process or some later date
prior to start-up. To check circuit breaker operation,
follow the operational procedures outlined in Section 3 for
both manually operated and electrically operated circuit
breakers.
1

Magnum
16 1812.900A
3 CIRCUIT BREAKER DESCRIPTION
AND OPERATION
3.1 Introduction
Magnum circuit breakers are available in three physical
frame sizes and in both drawout and fixed mounting
configurations (Figure 2-5 and Figure 3-2). A majority of
features are common to both configurations, and will be
discussed in this section. The mounting features unique
to the drawout and fixed configurations will be covered
individually in Sections 4 and 5 respectively.
Controls and indicators for both drawout and fixed circuit
breakers are functionally grouped on the front of the
circuit breaker. The front escutcheon (faceplate) is
common for the three frame sizes that cover all
continuous current ratings through 6300 amperes.
Double Wide frame circuit breakers utilize six (or eight)
sets of rear primary connections; these circuit breakers
are available from the factory with several different phase
sequences, distinguishable by the sixth character in the
model number (Figure 1-3). The phase sequence is also
labeled on the rear of the circuit breaker (Figure1-3).
For drawout breakers, phase sequence labels are also
supplied with the cassette and must be applied by the
switchgear builder. Circuit brakers with different phase
sequences are not interchangeable. Drawout breakers
with differing phase sequence are prevented from
insertion into the cassette by properly assembled
rejection key plates (see section 2.6.1).
Figure 3-1: Typical Drawout Circuit Breaker Features (Front and Rear Views)
1. Baffled Arc Chute Cover
2. Secondary Disconnects (Contacts)
3. Faceplate (Front Cover)
4. Drawout Rail Supports
5. Integral Lifting Handle
6. Primary Disconnect Finger Cluster
7. Arc Chamber
8. Tripper Bar
9. Sensor Rating Viewing Window
10. Levering Device Bearing Plate
11. Padlockable Levering Device Access Door
12. Circuit Breaker Nameplate
1 5 8 4
10
12 11 3
2 7
6
9

Magnum
1812.900A 17
Figure 3-2: Typical Fixed Circuit Breaker Features (Front and Rear Views)
1. Baffled Arc Chute Cover
2. Secondary Disconnect
3. Faceplate (Front Cover)
4. Integral Lifting Handle
5. Fixed Horizontal Primary Terminal
6. Fixed Primary Terminal (with optional Vertical Adapter)
7. Arc Chamber
8. Sensor Rating Viewing Window
9. Mounting Foot
10. Circuit Breaker Nameplate
11. Tripper Bar
2 1 6
10 3 9
4 11
8 5
7

Magnum
18 1812.900A
Figure 3-3: Typical Double-wide Standard Frame Fixed Circuit Breaker Features (Front and Rear Views)
1. Baffled Arc Chute Cover
2. Secondary Contact Connector
3. Faceplate (Front Cover)
4. Integral Lifting Handle
5. Fixed Vertical Primary Terminals with Optional Vertical Adaptor
6. Arc Chamber
7. Mounting Foot
8. Circuit Breaker Nameplate
9. Phase Identification Labels
10. Tripper Bar
2
1
10
4
7
8
3
9 6 5

Magnum
1812.900A 19
Red = Connect
Yellow = Test
Green = Disconnect
Figure 3-4: Typical Drawout Circuit Breaker Features (Front and Rear Views)
1. Trip Flag (Pop Out Indicator)
2. Three Accessory Windows
3. Trip Unit
4. Rating Plug
5. Contact Status (Open-Close)
6. Spring Status (Charged-Discharged)
7. Manual “OFF” Button (Push)
8. Manual “ON” Button (Push)
9. Manual Charge Handle
10. Optional Operation Counter
11. Padlockable Levering Device Access Door for Drawout Breaker
12. Color Coded-Breaker Position Indicator
13. Nameplate
14. Trip Unit Test Port
15. Trip Unit Cover with Two Mounting Screws (Mounting Screws will Accept Customer Supplied Lead
Security Meter Seals
12
7
10
11
13
15
14
5
8
1 2
3
9
6

Magnum
20 1812.900A
3.2 Basic circuit breaker assembly
Magnum circuit breakers use a rigid frame housing
construction of engineered thermoset composite resins.
This construction provides high strength structural
properties, excellent dielectric characteristics and
resistance to arc tracking.
The 3-piece construction approach provides support while
isolating and insulating power conductors (Figure 3-5):
1. A 2-piece engineered thermoset composite resin case
encloses current paths and arc chambers. The chambers
act to channel arc gases up and out of the circuit breaker
during interruption.
2. The operating mechanism sits on the front of the case
and is electrically isolated and insulated from current
contact structures. It is covered by an insulating front
cover.
3.3 Pole units
A current carrying pole unit is individually enclosed and
rigidly supported by the case.
The individual chambers provide for pole unit isolation and
insulation from one another. Each pole unit has one
primary contact assembly, which consists of a moving
portion and a fixed portion. The exact design
configuration depends upon the breaker’s frame size.
Double-wide circuit breakers use two pole units and arc
chute assemblies connected mechanically and electrically
in parallel to form each phase.
Figure 3-5: Typical Magnum Construction (Right Side View)
1. Case
2. Front Cover
3.3.1 Primary moving contacts
Depending upon the frame size, each primary moving
contact assembly is comprised of multiple individual
copper contact fingers connected to the load conductor
through flexible braided connectors (Figure 3-6). Two
flexible connectors are used to connect each finger to the
load conductor. The number of fingers used depends
upon the circuit breaker’s continuous and short-circuit
current ratings (Figure 3-7 and Figure 3-8). On some
ratings fingers are removed and replaced with spacers.
The single contact finger performs both the main and
arcing contact functions on different parts of the same
finger (Figure 3-6). A highly conductive alloy pad is part of
the contact finger and functions as the moving main
contact, and is called the “Heel.” The tip of the same
contact finger functions as the moving arcing contact, and
is called the “Toe.”
Figure 3-6: Features of Magnum Moving Conductor
Assembly
1. Pivot Point
2. Single Contact Finger
3. Moving Arcing Contact Area (Toe)
4. Moving Main Contact Conductive Pad (Heel)
5. Dual Flexible Connections
1
2
1
3
2
5 4