mcgraw-edison FUSES

Product Overview

NX Fuses

NX Indoor Current Limiting FuseS


Cooper Power Systems Type NX current-limiting fuses provideoverload protection for all indoor and underground cable distribution systems 2.4 through 34.5 kV. NX fuses are noiseless and expel no hot gases or burning particles while interrupting currents from minimum melt to maximum fuse rating (50,000 A through 23 kV, 35,000 A through 27 and 38 kV). Their currentlimiting capability greatly reduces the momentary duty on protected equipment, extending the life and, in some cases, reducing the original cost of that equipment.

The function of the fuse tube is to confine the arc and produce arcquenching gases which are expelled from the end of the tube.  Voltage stress across the fuse tube is eliminated by the gap between the end of the fuse tube and the capacitor terminal. There is no possibility of tracking and eventual flashover, even after exposure to weather and contaminants. When the spring ejects the leader, positive indication of a blown fuse can also be easily detected from a distance.

The ability of an NX fuse to interrupt low-current faults eliminates the need for auxiliary devices to handle these
troublesome current levels. An NX fuse extends system coordination because it is fast clearing and current-limiting
– conductor and equipment damage caused by high currents is virtually eliminated.


The basic NX fuse unit is designed to mount in a clip-style mounting. Basic clip-style NX fuses are available in 4.3, 5.5, 8.3, 15.5, 23, 27, and 38 kV ratings.


An NX fuse with an Arc-Strangler loadbreaking device, (see Figure 2) that mounts in a hinge-style mounting is available on 4.3, 5.5, 8.3, and 15.5 kV fuses. All current magnitudes from excitation current through 200 A can
be interrupted positively and safely by opening the fuse with a switch disconnect stick.

These units have the same operating characteristics as the basic clipstyle fuse, along with loadbreaking capabilities.

Arc-Strangler Switchblade
Switchblades with the Arc-Strangler
loadbreaking device are available in 8.3 and 15.5 kV, 200 A.

NX® Companion® Il Back-up Current-Limiting Fuse


The Cooper Power Systems NX® Companion® ll fuse is designed to be conveniently applied as an add-on, back-up, currentlimiting fuse. The Companion II back-up fuse will interrupt high fault current and at the same time, limit the amount of energy that is let-through to the protected equipment. This fuse is designed to be applied in series with an expulsion or other type of weak link fuse. This series connected fuse must be capable of  interrupting both excessive overload currents and low to intermediate fault currents up through the minimum interrupting rating of the Companion II fuse. If the expulsion fuse is applied within the recommended guidelines, enough current will be let-through to melt the expulsion fuse. When the expulsion fuse is in a cutout, the resulting drop open action provides, in any fault situation, a positive blown fuse indication for operating personnel.

The majority of faults on distribution systems are of low magnitude (such as transformer overloads or incipient faults), and normally only the lower cost expulsion fuse melt and clear the fault. The available fault current on many overhead distribution systems, however, has grown beyond the interrupting ratings of the expulsion fuse. When
the Companion II fuse is used, and a higher magnitude fault current occurs, the possibility of eventful transformer failure is greatly reduced.

The Companion II fuse offers major advantages over other back-up, current-limiting fuses in the industry. This design offers a small, compact, reliable fuse that is easier to handle in field installations. The modular design also offers greater flexibility in the selection of terminal options and the ability to re-use the terminals after a fuse operation.

Every Companion II fuse is I2t tested. This assures operation of the fuse only at published minimum melt I2t levels and above, guaranteeing that a Companion II fuse will not be susceptible to nuisance operations at lower I2t levels. This Cooper Power Systems patented quality-control test detects defects that cannot be identified by any
other test procedure, including resistance checks and x-rays. The standard 8.3 kV and 17.2 kV, 25 K Companion II fuse is also manufactured as a “Tandem ELF™ Ready” fuse and can be used in the Cooper Power Systems Tandem
ELF fuse product. The Tandem ELF fuse combines the series fuse link and Companion II fuse in one hookstick
removable design which eliminates the need to separately connect the Companion II fuse.


The Companion II back-up currentlimiting fuse will interrupt high magnitude fault currents while also limiting the amount of current and energy let-through to the transformer. The back-up current-limiting fuse will limit the let-through current to minimize the possibility of transformer tank rupture from high magnitude internal faults or to minimize damage to the tank or bushing that might result from bushing flashovers.


The operation of the Companion II back-up current-limiting fuse will enhance power quality of the system and improve service continuity during high magnitude faults. The duration of the voltage dip associated with system short circuits will be limited to the short melt time of the Companion II fuse. Immediately after melting, the arc voltage generated by the current-limiting fuse will support system voltage until the fault is interrupted by the fuse. For high fault currents, the duration of the voltage dip associated with the melt time of the Companion II fuse
will be well within the allowable limits for sensitive electronic equipment as defined by CBEMA curves.

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Isolation Link


Cooper Power Systems isolation links provide extra protection during refusing and switching operations when used in series with a Bay-O-Net type fuse or MagneX Interrupter.  

Isolation links are not fuses and do not have an interrupting rating. During a transformer failure, the isolation link will melt so that the opened primary circuit of a faulted transformer cannot be re-energized by the line crew.


Isolation links are used in series with Cooper Power Systems Bay-O-Net type expulsion fuses to provide extra
protection during re-fusing operations.  They are coordinated to operate at high current levels that are typical of a
transformer failure.


Isolation links are also used in series with the Cooper Power Systems MagneX Interrupter to provide extra  protection during switching operations.  The MagneX isolation link has arc shortening tabs to reduce the arc
length and thus reduce the I2t energy released during operation. They are coordinated to operate at high current
levels that are typical of a transformer failure.


No special tools are required. Isolation links are bolted onto Bay-O-Net fuse assemblies or MagneX Interrupters in
series between the primary transformer bushing and primary coil.
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CMU Medium Voltage Power Fuses


The Cooper Power Systems CMU Power Fuse is a boric acid, expulsionstyle fuse. Suitable for both indoor and outdoor applications, the CMU Power Fuse provides an economical alternative to refillable fuses. 

CMU Expulsion Power Fuses are available in 3 maximum voltage classes: 17 kV, 27 kV, and 38 kV. The replaceable

fuse unit comes in 3 speed variations: Standard “E”, Slow “E”, and “K”. Amperage sizes range from 3 A through 200 A.

The CMU Power Fuse interrupting rating greatly exceeds that of conventional distribution cutouts that uses a fiber tube and fuse link design, and considerably reduces the hazards and noise of the violent exhaust common to cutouts under fault interrupting conditions. The CMU Power Fuse, employing the use of calibrated silver element, boric acid for its interrupting media and rod mechanism for arc extension, creates low arcing voltage and mild exhaust during fault interruption.


The CMU Power Fuses provide effective protection for circuits and equipment which operate on system voltages up to 34,500 V. They can be used on both electric utility and industrial distribution systems. Typical applications include:

■   Power Transformers
■   Feeder Circuits
■   Distribution Transformers
■   Potential Transformers
■   Station Service Transformers
■   Metal-enclosed Switchgear
■   Pad-Mount Switches
■   Overhead Capacitor Racks

CMU Power Fuses can be used in outdoor or indoor applications, and can be used to directly replace competitive
equivalent units.

When used in upstream system protection, the CMU Power Fuse operates promptly to limit the stress on electrical systems due to short circuits.  It provides isolation for the faulted circuit, limiting the size of interrupted service area.

Full protection is provided for downstream equipment, even down to minimum melt current, regardless of the nature of the fault. The CMU Power Fuse acts rapidly to take transformer and feeder circuits off-line before
damage can become widespread.

It provides excellent isolation for capacitors as well in the event of a fault condition. When installed on the primary side of substation power transformers, CMU Power Fuses provide protection against small, medium or large faults.


Tests are conducted in accordance with Cooper Power Systems quality assurance requirements.
■   Physical Inspection
■   Micro-Ohm Resistance Testing
■   Construction Integrity Testing


No special tools are required to install the CMU Power Fuse. The CMU Power Fuse and end fittings are designed to
fit into industry standard mountings.
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JOE E-Rated Current-Limiting Power Fuses


The Cooper Power Systems JOE current-limiting power fuses are
E-Rated per IEEE Std C37.46™ standard, providing an excellent choice
for protection of transformers, feeder circuits, high voltage switchgear, and metal-enclosed switchgear. Voltage ratings include 5.5 kV and 15.5 kV.  The fuses have either 2” or 3” diameter barrels (sometimes double-barrel) as indicated, and have standard clip center distances of 12”, 15” or 18”.  The fuses have ferrules for mounting in standard spring-reinforced clips, providing interchangeability with other brands of fuses. In addition,
the fuses are equipped with blownfuse indicators to provide positive
identification of the open fuse.

Cooper’s JOE current-limiting power fuses meet the IEEE Std C37.40™
standard definition for full-range current limiting fuses, providing superior protection to general-purposefusing alternatives.  Cooper’s currentlimiting
power fuses consistently clear low current faults, as well as reliably interrupt high magnitude short-circuit
currents. The fuses’ current-limiting capability limits both peak current magnitude and fault duration, thus
limiting the total I2t let-through energy.

fuses are designed to meet the stringent needs of industrial and utility applications. The noiseless operation
and lack of expulsion byproducts make them ideal for indoor application in confined spaces. They fit in industrystandard power fuse mountings and are suitable for both indoor and outdoor installations. These E-Rated
fuses have time-current characteristics that allow easy coordination with other upstream and downstream protective devices. Cooper’s current-limiting power fuses are used to protect transformers, feeder circuits, high
voltage switchgear, metal-enclosed switchgear and other equipment that can benefit from their energy-limiting


No special tools are required. The JOE fuse is designed for indoor and outdoor mounting in industry standard in-air clip mountings and fused disconnect switches.
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For additional information on McGraw Edison Fuses contact us at 918.665.6888, or use our fuse search tab at the top of the page. You can also request a quote on any of the McGraw Edison Fuses using our quote form.      

Part Number


Select part number for more specific information
FA5J10 8.3kV/10 Amps
FA5J18 8.3kV/18 Amps
FA5J25 8.3kV/25 Amps
FA5J30 8.3kV/30 Amps
FA5J40 8.3kV/40 Amps
FA5J45 8.3kV/45 Amps
FA5J65 8.3kV/65 Amps
FA6J10 15.5kV/10 Amps
FA6J18 15.5kV/18 Amps
FA6J25 15.5kV/25 Amps
FA6J30 15.5kV/30 Amps
FA6J40 15.5kV/40 Amps
FA6J45 15.5kV/45 Amps
FA6J65 15.5kV/65 Amps
FA7J12 23kV/12 Amps
FA7J18 23 kV/18 Amps
FA7J25 23 kV/25 Amps
FA1H18 4.3 kV/18 Amp
FA1H25 4.3 kV/25 Amp
FA1H35 4.3 kV/35 Amp
FA1H45 4.3 kV/45 Amp
FA1H50 4.3 kV/50 Amp
FA1H65 4.3 kV/65 Amp
FA1H75 4.3 kV/75 Amp
FA1H100 4.3 kV/100 Amp
FA2H6 4.3 kV/6 Amp
FA2H8 4.3 kV/8 Amp
FA2H10 4.3 kV/10 Amp
FA2H12 4.3 kV/12 Amp
FA2H18 4.3 kV/18 Amp
FA2H20 4.3 kV/20 Amp
FA2H25 4.3 kV/25 Amp
FA2H30 4.3 kV/30 Amp
FA2H40 4.3 kV/40 Amp
FA2H50 4.3 kV/50 Amp
FA2H65 4.3 kV/65 Amp
FA2H75 4.3 kV/75 Amp
FA3H1 5.5 kV/1.5 Amp
FA3H3 5.5 kV/3 Amp
FA3H4 5.5 kV/4 Amp
FA3H6 5.5 kV/6 Amp
FA3H8 5.5 kV/8 Amp
FA3H10 5.5 kV/10 Amp
FA3H12 5.5 kV/12 Amp
FA3H18 5.5 kV/18 Amp
FA3H20 5.5 kV/20 Amp
FA3H25 5.5 kV/25 Amp
FA3H30 5.5 kV/30 Amp
FA3H40 5.5 kV/40 Amp
FA3H50 5.5 kV/50 Amp
FA3H65 5.5 kV/65 Amp
FA3H80 5.5 kV/80 Amp
FA3H100 5.5 kV/100 Amp
FA4H1 15.5kV/1.5 Amp
FA4H3 15.5kV/3 Amp
FA4H4 15.5kV/4.5 Amp
FA4H6 15.5kV/6 Amp
FA4H8 15.5kV/8 Amp
FA4H10 15.5kV/10 Amp
FA4H12 15.5kV/12 Amp
FA4H18 15.5kV/18 Amp
FA4H20 15.5kV/20 Amp
FA4H25 15.5kV/25 Amp
FA4H30 15.5kV/30 Amp
FA4H40 15.5kV/40 Amp
FA4H50 15.5kV/50 Amp
FA4H65 15.5kV/65 Amp
FA4H80 15.5kV/80 Amp
FA4H100† 15.5kV/100 Amp
FA5H6 23kV/6 Amp
FA5H8 23kV/8 Amp
FA5H10 23kV/10 Amp
FA5H12 23kV/12 Amp
FA5H18 23kV/18 Amp
FA5H20 23kV/20 Amp
FA5H25 23kV/25 Amp
FA5H30 23kV/30 Amp
FA5H40 23kV/40 Amp
FA9H6 27kV/6 Amp
FA9H8 27kV/8 Amp
FA9H10 27kV/10 Amp
FA9H12 27kV/12 Amp
FA9H15 27kV/15 Amp
FA9H18 27kV/18 Amp
FA9H20 27kV/20 Amp
FA9H25 27kV/25 Amp
FA9H30 27kV/30 Amp
FA9H40 27kV/40 Amp
FA9H50 27kV/50 Amp
FA10H6 38kV/6 Amp
FA10H8 38kV/8 Amp
FA10H10 38kV/10 Amp
FA10H12 38kV/12 Amp
FA10H18 38kV/18 Amp
FA10H20 38kV/20 Amp
FA10H25 38kV/25 Amp
FA10H30 38kV/30 Amp
FA10H40 38kV/40 Amp
FA10H50 38kV/50 Amp
FA1A18 4.3kV/18 Amp
FA1A25 4.3kV/25 Amp
FA1A35 4.3kV/35 Amp
FA1A45 4.3kV/45 Amp
FA1A50 4.3kV/50 Amp
FA1A65 4.3kV/65 Amp
FA1A75 4.3kV/75 Amp
FA1A100 4.3kV/100 Amp
FA2A6 5.5kV/6 Amp
FA2A8 5.5kV/8 Amp
FA2A10 5.5kV/10 Amp
FA2A12 5.5kV/12 Amp
FA2A18 5.5kV/18 Amp
FA2A20 5.5kV/20 Amp
FA2A25 5.5kV/25 Amp
FA2A30 5.5kV/30 Amp
FA2A40 5.5kV/40 Amp
FA2A50 5.5kV/50 Amp
FA2A65 5.5kV/65 Amp
FA2A75 5.5kV/75 Amp
FA3A1 8.3kV/1 Amp
FA3A3 8.3kV/3 Amp
FA3A4 8.3kV/4 Amp
FA3A6 8.3kV/6 Amp
FA3A8 8.3kV/8 Amp
FA3A10 8.3kV/10 Amp
FA3A12 8.3kV/12 Amp
FA3A18 8.3kV/18 Amp
FA3A20 8.3kV/20 Amp
FA3A25 8.3kV/25 Amp
FA3A30 8.3kV/30 Amp
FA3A40 8.3kV/40 Amp
FA4A1 15.5kV/1 Amp
FA4A3 15.5kV/3 Amp
FA4A4 15.5kV/4 Amp
FA4A6 15.5kV/6 Amp
FA4A8 15.5kV/8 Amp
FA4A10 15.5kV/10 Amp
FA4A12 15.5kV/12 Amp
FA4A18 15.5kV/18 Amp
FA4A20 15.5kV/20 Amp
FA4A25 15.5kV/25 Amp
FA4A30 15.5kV/30 Amp
FA4A40 15.5kV/40 Amp

NX Companion II Fuse

FAH8KV12K 12K/50 Amp
FAH8KV25K 25K/50 Amp
FAH8KV40K 40K/50 Amp
FAH17KV12K 12K/43 Amp
FAH17KV25K 25K/43 Amp
FAH17KV40K 40K/43 Amp
FAH23KV12K 12K/31 Amp
FAH23KV25K 25K/31 Amp
CMU702003 3k/2k-200K Amp
CMU702006 6k/2k-200K Amp
CMU702008 8k/2k-200K Amp
CMU702010 10k/2k-200K Amp
CMU702012 12k/2k-200K Amp
CMU702015 15k/2k-200K Amp
CMU702020 20k/2k-200K Amp
CMU702025 25k/2k-200K Amp
CMU702030 30k/2k-200K Amp
CMU702040 40k/2k-200K Amp
CMU702050 50k/2k-200K Amp
CMU702065 65k/2k-200K Amp
CMU702080 80k/2k-200K Amp
CMU702100 100k/2k-200K Amp
CMU702140 140k/2k-200K Amp
CMU702200 200k/2k-200K Amp
CMU612005 5E/5E-200E Amp
CMU612007 7E/5E-200E Amp
CMU612013 13E/5E-200E Amp
CMU612015 15E/5E-200E Amp
CMU612020 20E/5E-200E Amp
CMU612025 25E/5E-200E Amp
CMU612030 30E/5E-200E Amp
CMU612040 40E/5E-200E Amp
CMU612050 50E/5E-200E Amp
CMU612065 65E/5E-200E Amp
CMU612080 80E/5E-200E Amp
CMU612100 100E/5E-200E Amp
CMU612125 125E/5E-200E Amp
CMU612150 150E/5E-200E Amp
CMU612175 175E/5E-200E Amp
CMU612200 200E/5E-200E Amp
CMU712015 15E/15SE-200SE Amp
CMU712020 20E/15SE-200SE Amp
CMU712025 25E/15SE-200SE Amp
CMU712030 30E/15SE-200SE Amp
CMU712040 40E/15SE-200SE Amp
CMU712050 50E/15SE-200SE Amp
CMU712065 65E/15SE-200SE Amp
CMU712080 80E/15SE-200SE Amp
CMU712100 100E/15SE-200SE Amp
CMU712125 125E/15SE-200SE Amp
CMU712150 150E/15SE-200SE Amp
CMU712175 175E/15SE-200SE Amp
CMU712200 200E/15SE-200SE Amp
CMU703003 3k/3k-200K Amp
CMU703006 6k/3k-200K Amp
CMU703008 8k/3k-200K Amp
CMU703010 10k/3k-200K Amp
CMU703012 12k/3k-200K Amp
CMU703015 15k/3k-200K Amp
CMU703020 20k/3k-200K Amp
CMU703025 25k/3k-200K Amp
CMU703030 30k/3k-200K Amp
CMU703040 40k/3k-200K Amp
CMU703050 50k/3k-200K Amp
CMU703065 65k/3k-200K Amp
CMU703080 80k/3k-200K Amp
CMU703100 100k/3k-200K Amp
CMU703140 140k/3k-200K Amp
CMU703200 200k/3k-200K Amp
CMU613005 5E/5E-200E Amp
CMU613007 5E/5E-200E Amp
CMU613010 5E/5E-200E Amp
CMU613013 5E/5E-200E Amp
CMU613015 5E/5E-200E Amp
CMU613020 2E/5E-200E Amp
CMU613025 25E/5E-200E Amp
CMU613030 30E/5E-200E Amp
CMU613040 40E/5E-200E Amp
CMU613050 50E/5E-200E Amp
CMU613065 65E/5E-200E Amp
CMU613080 80E/5E-200E Amp
CMU613100 100E/5E-200E Amp
CMU613125 125E/5E-200E Amp
CMU613150 150E/5E-200E Amp
CMU613175 175E/5E-200E Amp
CMU613200 200E/5E-200E Amp
CMU713015 15E/15SE-200E Amp
CMU713020 20E/15SE-200E Amp
CMU713025 25E/15SE-200E Amp
CMU713030 30E/15SE-200E Amp
CMU713040 40E/15SE-200E Amp
CMU713050 50E/15SE-200E Amp
CMU713065 65E/15SE-200E Amp
CMU713080 80E/15SE-200E Amp
CMU713100 100E/15SE-200E Amp
CMU713125 125E/15SE-200E Amp
CMU713150 150E/15SE-200E Amp
CMU713175 175E/15SE-200E Amp
CMU713200 200E/15SE-200E Amp
CMU704003 3k/3k-200K Amp
CMU704006 6k/3k-200K Amp
CMU704008 8k/3k-200K Amp
CMU704010 10k/3k-200K Amp
CMU704012 12k/3k-200K Amp
CMU704015 15k/3k-200K Amp
CMU704020 20k/3k-200K Amp
CMU704025 25k/3k-200K Amp
CMU704030 30k/3k-200K Amp
CMU704040 40k/3k-200K Amp
CMU704050 50k/3k-200K Amp
CMU704065 65k/3k-200K Amp
CMU704080 80k/3k-200K Amp
CMU704100 100k/3k-200K Amp
CMU704140 140k/3k-200K Amp
CMU704200 200k/3k-200K Amp
CMU614005 5E/5E-200E Amp
CMU614007 7E/5E-200E Amp
CMU614010 10E/5E-200E Amp
CMU614013 13E/5E-200E Amp
CMU614015 15E/5E-200E Amp
CMU614020 20E/5E-200E Amp
CMU614030 30E/5E-200E Amp
CMU614040 40E/5E-200E Amp
CMU614050 50E/5E-200E Amp
CMU614065 65E/5E-200E Amp
CMU614080 80E/5E-200E Amp
CMU614100 100E/5E-200E Amp
CMU614125 125E/5E-200E Amp
CMU614150 150E/5E-200E Amp
CMU614175 175E/5E-200E Amp
CMU614200 200E/5E-200E Amp
CMU714015 15E/15SE-200SE Amp
CMU714020 20E/15SE-200SE Amp
CMU714025 25E/15SE-200SE Amp
CMU714030 30E/15SE-200SE Amp
CMU714040 40E/15SE-200SE Amp
CMU714050 50E/15SE-200SE Amp
CMU714065 65E/15SE-200SE Amp
CMU714080 80E/15SE-200SE Amp
CMU714100 100E/15SE-200SE Amp
CMU714125 125E/15SE-200SE Amp
CMU714150 150E/15SE-200SE Amp
CMU714175 175E/15SE-200SE Amp
CMU714200 200E/15SE-200SE Amp
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