ETON MCCB.pdf

8/15/2019 ETON MCCB.pdf

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Technical paper

Dipl.-Ing. Wolfgang Esser

Second, supplemented edition 2011

Molded case circuit breakers

for applications in North America

Molded case circuit breakersfor USA and Canada www.eaton.com/moellerproducts


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Molded case circuit breakers for

applications in North America

Topic Page

Introduction and summary overview 3

Focus on key sections 5

Remarks 5

Introduction: Foreign lands, foreign rules 6

Equipment for world markets, or market specific product lines 6

IEC- Rating data and the CE- Mark equipment for North America 8

Applications of power components per various North American Standards 9

Certification categories per North American standards 9

Interaction of panel builders and users of certified components 11

Overview of the North American product line: Molded case circuit breakers,

switch-Disconnectors and molded case switches 12

„Typical North American“ circuit breakers in energy distribution circuits 16

– for non-motor loads 16

– for motor loads 17

Circuit breakers with adjustable overload trips 19

Motor Protection/Systems Protection 19

Additional requirements for circuit breakers in motor protective applications 19

Requirements for motor starters on the North American market 19

Instantaneous-Trip circuit breakers, a crucial component of North American combination motor starters 24

Motor protective circuit breakers type NZM – and more 28Circuit breakers for various applications on the North American market 31

Circuit breaker trip curves (and trip setting guidelines) 32

Current interrupting designs of molded case circuit breakers

– Zero point clearing, or devices with current limiting capabilities 34

Current limiting circuit breakers for use in Industrial Control Panels per UL 508A 38

Switch-Disconnectors N or Molded Case Switches NS 40

Advantages of circuit breakers over fuses in North American feeder and branch circuits 42

Use of certified accessories for the panel builder 43

New busbar system SASY 60i opens up new possibilities in the assembly of control panels

featuring circuit breakers 43

Special requirements on the use of circuit breakers and switches in North Americanengineered products and assemblies 46

Door interlocking provisions 48

Operating handles with North American environmental type ratings 50

The new supplementary handle with „deliberate action“ 54

The North American handle design with „vertical motion“ 57

Identification, warning markings and documentation 58

Additional requirements on the assembly of North American engineered products 58

Influence of supply network configurations on equipment selection 60

Listed (UL 489) circuit breakers type FAZ..-NA for small loads 60

Compact, high interrupting molded case circuit breaker Type PKZM4-..-CB 60

Validity 60Acknowledgement 61

Bibliography 61

Glossary 61


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Differences between relevant electricalstandards and market conventions inboth North America (primarily the USand Canada) and the IEC world playa key role in shaping the design anddetermining the proper application ofproducts such as NZM molded casecircuit breakers and NS molded caseswitches, N , PN switch-disconnectors,and combination motor starters inthose markets.

North American electrical product

standards differentiate in signifi-cant respect between equipmentdeemed suitable for energy distribu-tion (such as UL 489) [1] versus thosecomponents normally groupedunder industrial control (per UL 508/ UL60947) [2]. This type of differentia-tion is not known in the IEC world. Thebasis for many design engineeringerrors from the IEC side, for examplein motor starter circuits, was thus oftenrooted in the commonly misunderstoodpractice in North America of exclusively

assigning the protective function inthose circuits to devices with specificconstruction requirements, such asthose featuring larger electrical clear-ances per standards like UL 489 resp.CSA-C22.2 No. 5-09, and the seeminglyredundant need to place them aheadof motor protective devices, deemedto be self-protective in the IEC world,but meeting only the arguably lessstringent constructional requirementsof industrial control standards such asUL 508 and CSA-C22.2 No. 14. It is

always quite a revelation, therefore,that proper design of such branchcircuits will often times require the useof additional protective devices such ascircuit breakers and fuses, a practicewhich is mostly deemed unnecessaryin the IEC world.

The classic IEC style manual motorprotective switch, e.g. a PKZM0, in itsstandard design, would fall short ofcircuit breaker requirements per NorthAmerican product standards. For one,

the harmonized editions of the UL489 and CSA-C22.22 No. 5-09 circuitbreaker standards constructionallyrequire the use of much larger elec-trical clearances than deemed neces-sary by comparative IEC/EN standards.

Physically smaller protective devices,such as the PKZM0, are more especiallyaffected by this distinction since theyare widely known and accepted in theIEC world as one of the most compacthigh performance circuit breaker designsavailable anywhere. The confusion iscompounded by the fact that many othermanufacturers of similar equipmentalso freely refer to their own devices ascircuit breakers in ads and printed litera-ture. This problem, however, has beensomewhat alleviated in recent years

with the introduction of new certifica-tions in North America. Motor protectorswith Type E and F certification [3] perUL 508 can now be equipped with largespacing incoming terminals and providestand-alone branch circuit protectionfor individual motor starter circuits. Still,these applications are relegated solelyto motor circuits, and can come withadditional restrictions, such as usagein solidly grounded networks only, e.g.480Y/277VAC, or slash rated systemsper the electrical codes.

The molded case circuit breaker andswitch series, types NZM 1..-...-NAthrough NZM 4..-...-NA, was developed tooptimally fulfill all of the North Americanrequirements for these products. AllNorth American versions of the line arecertified per the demanding UL 489standard. Special versions for motorprotection fulfil additional calibrationrequirements per the industrial controlstandard UL 508. Because the NorthAmerican versions are identical to the IEC

line dimensionally, panel design for bothmarkets can follow very similar layouts.Alternatively, North American deviceswith suffix „-NA“ can be used as worldmarket products globally, since they alsomeet all pertinent IEC component perfor-mance standards, and are CE marked.

The paper categorizes the Moeller seriesof circuit breakers from Eaton per thefollowing criteria:• Type of certification,• Their switching and protective functions,

• Their correlation to product certificationstandards such as UL 489 and UL 508

• Their technological capabilites whencombined with multi-function trip mod-ules that customize breakers to bestsuit the application.

The line was designed to conform toNorth American market conventions,including component markings andaccompanying installation instructionsheets. Circuit breakers with fixed over-load trips are very seldom used in theIEC world (except possibly in Asia, or inthe residential market). North Americanframe sizes often take on nominalcurrent values which are not consideredtypical throughout the IEC world. Certainversions of the breakers have also under-gone additional calibration testing per

the industrial control standards to qualifytheir use as motor overload protectivedevices (Table 1). Switch-disconnectorswith integrated short-circuit trips are newto the IEC, but are a common feature ofNorth American molded case switches.Both products are very often used as thesupply circuit disconnecting means inengineered assemblies such as industrialcontrol panels.

Search assistance and classification of

switch styles

The following pages will present manyvariations of switch-disconnectors andcircuit breakers, along with the mannerin which they are most commonlyapplied. In order to help the readernavigate more effectively throughall the various tables, the paper willmake use of „Switch Style“ categorycodes, with additional letter qualifierssuch as A, B, C, D and E. In addition,orientation will be supported with color

coding of fields and sections. Thesequalifier letters are in no way relatedto any similar designations used inthe electrical standards, such as thoseused to identify combination motorstarter “construction types” in theindustrial control standards. This formof internal coding was selected foruse in this paper only, and does notappear in any other Eaton publication.Actual selection and/or combinationof Eaton components is best carriedout through the use of assigned part

numbers and article numbers providedin main catalogs.

The circuit breaker selection process isfairly straight-forward, even for the more

Introduction and

summary overview


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demanding applications such as motorbranch circuits. Eaton offers the OEM orpanel builder at least two viable alterna-tives, both technically and economically:

• The more conventional North Ameri-can combination motor startersolution, consisting of 3 compo-nents

• UL 489 – Instantaneous Trip circuitbreakers NZM..-S(E)..-CNA

• UL 508 – Motor controller (contac-tor) DIL M

• UL 508 – Motor overload relay ZBor ZEV

or• UL 489 – Inverse time, fixed over-

load trip circuit breaker NZM..-A(E) F..- NA oder NZM..- VEF..-NA

• UL 508 – Motor controller (contac-tor) DIL M

• UL 508 – Motor overload relay ZBor ZEV

• Or a combination motor startersolution more in line with IEC con-ventions, consisting of 2 compo-nents, which are also certifed perUL and CSA standards:

• UL 489 – Inverse time circuitbreaker NZM..-ME...-NA withadditional motor overload calibra-tion per UL 508 -

• UL 508 – Motor controller (contac-

tor) DIL M .

The paper will also discuss in greaterdetail the use of current limiting circuitbreakers, which can play a special rolein the determination of the overall shortcircuit current rating (SCCR) of an indus-trial control panel per the SupplementSB [4] of the UL 508A standard. Finally,the paper will address differing NorthAmerican requirements with respectto the operating means of disconnectswitches used in assemblies falling

under the industrial machinery scope ofUL 508A and NFPA 79 [5]. The selec-tion of suitable operating handles forsupply circuit main disconnect switchescan be a common source of errors inthe design of equipment exported to

Suitability for main and supplemental applicationsMain applications Supplemental

applicationsType Search reference

help guide for thispaper

ShortCircuitProtec-tion

Inverse Time, short circuit and overload protection for:

Energydistribu-tionsystems

Cables Genera-torsTrans-formers

Selectivenetworkswith inten-tionally

delayed shortcircuit trips

Motors Maindiscon-nectswitch

Emer-cencyOFFswitch

Refer tothesetablesfor moredescriptive

informa-tionon eachtype

Switchstyles(InternalClassifica-tion code

for eachswitch typedescribedin thispaper)

1) X X NS..-..-NA 11 A

X 2) (X) 3) (X) 5) (X) 5) NZM..-S..-CNA 17 a/b B.1

X 2) (X) 3) (X) 5) (X) 5) NZM..-SE..-CNA 18 B.2

X X (X) 3)

(X) 3)

(X) 3)

X X NZM..-AF-..-NA 13 a/b/c C.1

X X X X NZM..-AEF..-NA 14 C.2

X X X X X X NZM..-VEF..-NA 21/23 C.3

X X (X) 3) X X NZM..-A..-NA 15 D.1

X X (X) 3) X X NZM..-AE..-NA 16 D.2

X X X X (X) 3) X X NZM..-VE..-NA 22/23 D.3

X X X 4) X X NZM..-ME..-NA 20 E

(X) Conditionally applicable, motor overload function provided by separately furnished overload relay.1) Switches have internal self-protection, up the maximum short circuit ratings shown in Table 12) For use only in certified combination motor controllers per North American electrical codes and standards.3) For use only in combination with suitable motor contactor and overload relay4) For use only in combination with suitable motor contactor5) For use only in individual motor controller branch circuits

Table 1: The significance of the table coloring scheme is explained in the body of the paper. The table shows the suitability of eachswitch style for any given application. The use of additional switching and protective devices may be required depending on theapplication.

Eaton molded case circuit breakerType Internal classifi-

cation code usedin this paper:Switch style

Certification inthe US per:

NS..-..-NA A UL 489

NZM..-S..-CNA B.1 UL 489

NZM..-SE..-CNA B.2 UL 489

NZM..-AF..-NA C.1 UL 489

NZM..-AEF..-NA C.2 UL 489NZM..-VEF..-NA C.3 UL 489

NZM..-A..-NA D.1 UL 489

NZM..-AE..-NA D.2 UL 489

NZM..-VE..-NA D.3 UL 489

NZM..-ME..-NA E UL 489

1) Switches have internal self-protection, up to themaximum short circuit ratings shown in Table 11

Table 2: Molded case circuit breaker and switch types Nmended for export to North America. All switch variatiocomponent, IEC style, motor branch circuit solutions formotor protective circuit breaker.


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tend to mimic IEC philosophies as closelyas possible. This is done intentionallysince modern machine manufacturers andpanel builders tend to overwhelminglyprefer solutions which can be universallyapplied. Comprehensive descriptions ofproduct certification testing and detailedconstruction aspects were purposelyomitted in order not to distract from theessential theme. Although the breadthof the paper is quite extensive, its focusdeals solely with fundamental aspects ofmolded case circuit breaker and switchdesign in North America, and their usagein certain key applications, such as motorcircuits. Design engineers involved incomplete electrical assembly project workwould best supplement their knowledgebase with additional information on NorthAmerican installation code requirements,as well as familiarize themselves morethoroughly with local market and applica-

tion based conventions.

In order to keep the paper as succinctand as clearly arranged as possible,discussions of the following topics:• Approval requirements per the NEC,

OSHA and CEC standards,• Basic certification requirements of pro-

tective and switching equipment forthe North American market

• Legal implications of the North Ameri-can electrical system and,

• Typical North American market conven-

tions

will also be referenced to a comprehen-sive technical paper already publishedand entitled „Special considerationsgoverning the application of ManualMotor Controllers and Motor Starters inNorth America“ [3]. This paper can berequested free of charge from Eaton inboth English and German or, as is thecase with a host of other North Americanexport related publications, available asa free download from the Internet. As is

the case with motor starters, the properapplication of circuit breakers in NorthAmerica needs to take into accountmany fundamental differences betweenthe requirements of that market forthose products, and what is typicallyapplicable and acceptable in the IECworld. The paper will thus elaborate onthe above themes only to the extent thatit is necessary for an understanding ofthe material presented herein. In areaswhere the paper specifically mentionsEaton products, it will be referencing the

newly introduced NZM 1.. through NZM4 line of molded case circuit breakersand switches. Similar offerings and solu-tions from previous generations of Eatoncircuit breakers and switches are notbeing addressed in this paper.

The paper makes references throughoutto established North American termi-nology such as Branch Circuit, FeederCircuit, Branch Circuit Protective Device,Short Circuit Current Rating etc. anddid not attempt to substitute equivalentEuropean terms. It was felt that usageof the proper North American referencesfor the purposes of this paper wouldprovide more clarity in the presentationof the informational content.

The US and Canada each possess theirown set of applicable electrical standards.For brevity purposes, the paper will oftensolely specify the applicable US basedstandard. For the most part, Canada willhave a corresponding standard, eithervery similar to, or in some cases, evenharmonized with the US document. Still,there are some outstanding differencesremaining in certain key standards from

both countries. Generally speaking,however, new standards or changes toexisting ones tend to originate mostly inthe US, with likely adoption or recognitioninto the Canadian system at a later date,most often with few changes.

Introduction:Foreign lands, foreign rules

Do you consider yourself a risk taker?It’s only natural to think about ways to

get around unfamiliar rules, but in theelectrical industry business, the conse-quences of running afoul of local NorthAmerican inspection authorities can beindeed quite penal. Admittedly, the IECstandards can also present their fairshare of seemingly ambiguous regula-tions, especially when one does not dealwith the requirements on a daily basis.As a general rule, Eaton much prefers tofollow the wiser route of minimizing risksby clearly understanding the regulationsahead of time so that assembly design

and equipment choices are more accurateand easier to plan. It’s certainly easier forour clients to have issues resolved in theearly stages of a project rather than waituntil problems surface down the road.When traveling by car through Europeone has to be aware that individual coun-tries may have their own driving laws andconventions in effect. Travel on the right,or the left, different speed limits etc...all valid reasons for drivers to be awareof, and respect, the travel rules in eachvisited country. It would be impossible to

find someone who could legitimately alterthe rules to fit their own particular travelwishes. Even the presence of a goodlawyer as a traveling companion wouldn’teliminate all the potential pitfalls of a veryunpleasant situation. Alone the risk of

breaking unknown laws in foreign coun-tries should be deemed a strong enoughdeterrent.

A similar parallel can be drawn withrespect to global standards for machineryand electrical equipment. Like arbitrarilyset speed limits on roads, the rules inelectrical standards can sometimesappear haphazardly put together and notalways logical. The only sure way, there-fore, is to deal with the requirementsdirectly, and ahead of time, howeverinconvenient that may be. Many of thehurdles can already be satisfied throughthe use of Eaton certified equipment. Onthe other hand, potential conflict issuesbeyond the use of certified product couldstill develop during the approval process.Some of these are not always explicitelyspelled out in the standards. Consultingcertification agencies during the design

stage is thus another useful way to avoidfuture problems. Assemblies destinedfor export to North America and certifedahead of time, i.e. labeling through a localUL or CSA panel builder, always standthe best chance of a smooth approvalprocess during the commissioning stagesat the final destination. If at all possible,direct contact with local approval authori-ties during the planning stages is alsoa great way to clarify any issues andmisunderstandings which could other-wise become a source of problems at

the installation site. Admittedly, that’s notalways possible, particularly in the caseof mass produced machinery whose finaldestination cannot be known ahead oftime. The panel builder should also takeinto consideration the difficulty of havingto subsequently modify an assemblyalready supplied to a job site in NorthAmerica. Doing so would inevitablyinvolve the intervention of local electricalcontractors to perform the work. If thedecision is made to risk the supply ofa non-compliant panel, then the panel

builder best have a sound back-up planin place to deal with potentially seriousregulatory issues related to the approvalprocess. As a general rule, Eaton recom-mends to avoid all risks by insuring thatall relevant North American requirementsin the assembly and design of exportrelated electrical equipment be strictlyfollowed at all times.

Equipment for world markets, ormarket specific product lines

Differences between electrical standardsand market conventions in both Europeand North America, if not properly takeninto consideration, can lead to unavoid-able delays in the approval process and


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the need for remedial actions on non-compliant assemblies (e.g. controls forindustrial machinery) in North America.The paper describes key design aspectsin this respect which are different inboth markets as they relate to theapplication of circuit breakers. The UL508A [4] standard for Industrial ControlPanels references at least 70 additionalstandards which could be of relevancewhen dealing with electrical controlassemblies for industrial machinery. As amanufacturer of electrical components,Eaton makes sure to comply with all therequirements in the relevant productstandards at the design stage in order toachieve certification and permit applica-tion in these assemblies. Of particularimportance is NFPA 79, the electricalstandard for industrial machinery.

A comprehensive knowledge base is vital

in the ability to design compliant NorthAmerican electrical assemblies. Havinga local presence on the continent canalso be an added bonus. The companySAE Schaltanlagenbau Erfurt GmbH isa partner of Eaton as well as a certifiedUL and CSA manufacturing location, andthey can be entrusted to undertake the

build and design of compliant electricalassemblies for North America. Eaton canalso name additional qualified buildersin other parts of Germany who regularlyinstall certified Eaton components intheir assemblies. These panel buildersare also staffed to competently under-take design and engineering duties.

European and North American Eatonemployees are also active participantsin important North American standardsorganizations, which enables them to beon top of all of the latest developments.

Eaton prefers to offer world marketdevices whenever a component designis able to satisfy the certification require-ments of both the North American andinternational standards relevant to thatproduct (Figure 1). The component isthen marked accordingly, and bears

rating and certification data from all themajor global product standards. Powercomponents such as motor contactorsand motor protectors, as well as controlcircuit pilot and signalling devices, fallinto this category. Circuit breakers andmolded case switches are often part ofseparate product lines, partly because

Requirements per

IEC and EN Standards

Requirements perUL and CSA Standards

IEC/EN product line UL/CSA product line

Both sets ofrequirements canbe accommodatedby one productdesign.

Negligible increasein certificationcomplexity

preferable outcome

World marketdevice

Additionalrequirements

for the NorthAmerican marketwould pushprices of IEC/EN productstoo high for themarket to bear.

It's not possible toreconcile both setsof requirements intoone product line.

products are subjectto additionalcertification costsbased on volume

there is periodicalre-examinationtesting required aswell as auditing ofmanufacturing facilitiesat regular intervals(Follow-up-Service)

and / or

and / or

Figure 1: In the interest of manageability from a logistics point of view, Eaton prefers, wherever possible, to offer a single version ofa product which carries all necessary certification markings for the global market place. Eaton refers to these components as WorldMarket devices. For certain products, such as circuit breakers, it’s not always technically possible to do so, or, certification testing percertain agencies would unnecessarily raise equipment prices for those markets not requiring that particular certification. In those cases,Eaton deems separate product ranges to be the better overall solution for customers. Manufacturers of high volume, serial productionmachinery will often standardize on products which bear North American certification marks for global usage. That is certainly a viableoption as long as the equipment is also in conformity with IEC standards, and bears a CE mark.

the appropriate standards in both majormarkets tend to be more divergent. Butthe reasons for the separation go beyondjust that, and are rooted in additionalcertification related expenditures whichmanufacturers must bear and which areonly applicable to product exported toNorth America. In isolated cases, seriousdiscrepancies between production andcertification reports could lead to produc-tion stoppage, a potential reality whichall manufacturers of certified equipmentmust face.

The ongoing production of certifiedequipment is closely monitored by theFollow-up-Service department of thirdparty certification agencies. Circuitbreakers are also additionally subjectto quaterly re-examination testingperformed by the Institute for Interna- tional Product Safety (I2PS) in Bonn,

which is an accredited facility within theEaton Group to perform these tests onbehalf of the certification agencies. Thetesting laboratory is thus empoweredto independently perform UL and CSAcertification testing for interested thirdparty clients such as switchgear manu-facturers and panel builders.


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Eaton equipment specifically certified forthe North American market is identifiedwith the suffix “-NA” or “-CNA” in theequipment part number. The differencesbetween both types will be describedin more detail in a later section entitled„North American certification catego-ries“. In Eaton parlance, the „-NA“ and“-CNA”, suffixes in the part numbersrelate to their suitability for installation inboth US and Canadian assemblies.

Also important: IEC rating data andthe CE mark on equipment for NorthAmerica.

The paper is primarily concerned withdiscussions of export related issues forequipment destined for North America.Naturally, a re-export of equipmentback towards the IEC world can also

occur. Smaller IEC designs have, in themeantime, gained better acceptanceamongst North American firms and the

general feeling is that it is better for ULand CSA certified equipment to alsobear IEC rating data and the CE markwhenever possible in order to allowtheir movement back into the EuropeanCommunity and the IEC world at large.Eaton has fulfilled that need with thisgeneration of circuit breakers. Gener-ally speaking, North American usersand modern machine manufacturersare very positively inclined towards theadvantages that many products whichmeet the requirements of the interna-tional machinery standard IEC/ EN 60204-1 [7] can offer, case in point thecircuit breakers and disconnect switchespresented in this paper.

IEC data will thus appear on NA versionsof equipment to the extent that theproduct meets the certification criteriaof both standards. Certain NA certified

switches also carry worldwide shipapprovals, and comply with the certi-fication requirements of Chinese and

Russian test agencies. The IEC ratingdata, however, only has limited appli-cability in North American installa-tions and usually serves best as refer-ence information.

There is also a growing trend amongstlarger European serial machine manufac-turers, for their world-wide production,to lean towards circuit breakers whichalso comply with the North Americancertification requirements. They simplywant to avoid stocking two variationsof the same switch. It’s a sensible costcutting decision on the part of manage-ment to reduce unnecessary inventories,i.e. the IEC switch can’t be installed inNorth America, whereas they are freeto globally apply the North Americanversion additionally marked with IECratings. In a previous chapter we haddescribed IEC components which met

North American requirements as “world-market” devices. Now the trend forcircuit breakers seems to be similar, this

Product Groupings in North America

Components for energy distribution Components for motor control

(Distribution Equipment) (Industrial Control Equipment)

e.g. UL 489, 98, 248, and CSA-C22.2 No. 4, 5-09, 248 UL 508/UL 60947 and CSA-C22.2 No.14

• Molded Case Circuit Breakers (UL 489)• Molded Case Switches (UL 489)• Enclosed and dead-front switches (UL 98)• (Non-)Fusible Disconnect Switches (UL 98)• Fuses (UL 248)UL:CSA equivalent standards:UL 98 : CSA-C22.2 No. 4UL 248: CSA-C22.2 No. 248

• Magnetic controllers (contactors)• Control Relays• Overload Relays• Manual Motor Controllers (protectors)• Rotary Cam Switches• Pushbuttons and Pilot Devices• Solid State controls and systems• Programmable Controllers

Special requirements: Special requirements:

• These devices need to be particularly robust in their con-struction and incorporate larger electrical clearances thanstandard industrial control equipment:

• (for 301...600 V: 1 Inch through air, 2 Inches over surface).• Lower permissible temperature rise (50 instead of 70 °C).• Product designs generally larger in size than IEC equivalent.• Incoming and outgoing feeder components for energy distri-

bution assemblies (Switchboards, Panelboards) must con-form to these standards.

• Main disconnect and protective switches in conformity withthese standards are also used in industrial control panelassemblies.

• Safety testing standards for these products are strictly main-tained, and factory production quality is closely monitoredthrough regular auditing by each certification agency.

• Quarterly re-examination testing of the production is alsoconducted by the approval authorities.

• UL/CSA Molded Case Circuit Breaker safety standards areamongst the most stringent in the industry world-wide.

• These components are constructionally smaller and electri-cal clearance sizing requirements are not as large as thosefor energy distribution equipment.

• Industrial control devices are installed primarily in controlpanels, in motor branch and associated load circuits, inMotor Control Centers (MCC) and also as components insome energy distribution assemblies.

• They can be combined in the same circuit as energy distri-bution equipment in control panels, e.g. in a motor branchcircuit together with a circuit breaker used for main discon-nect and protective functions.

• Factory production is also monitored by the certificationagencies, but not to the same extent as is generally applica-ble to molded case circuit breakers.

• Generally speaking, more compatible with conventional IEC-designs.

Table 3: Differences in North American product groupings, based on product safety standards such as UL 489 und CSA-C22.2 No. 5-09for molded case circuit breakers, and UL 508 und CSA-C22.2 No.14. for industrial control. „UL ...“ standards apply primarily in the US,with comparable „CSA...“ standards applicable in Canada. UL 98 = [8], UL 248-1 = [9]


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time with North American rated breakersand switches bearing IEC ratings andbeing able to fulfill the definition of a„world-market“ component.

Applications of power componentsper differing North Americanstandards

As shown in greater detail in Table 3 anotable differentiation is made in the USand Canada between equipment thatis designed primarily for use in supplyor feeder circuits (Distribution equipment , like molded case circuit breakersper UL 489 [1]) versus that which ismore commonly encountered in branchcircuits, such as Industrial controlequipment , per standards like UL 508[2]. A list of commonly encountered stan-dards applicable to both product catego-

ries is shown in the table. Each placesvarying sets of requirements on compo-nents, depending on which categorythey fall under. Typically, components willbe evaluated per one of the applicablestandards. In a later section of the paperwe’ll discuss how additional evaluationscan sometimes be done to differentstandards in order to broaden the scopeof application for that product, as well ashelp streamline component selection. Anexample of this would be UL 489 certifi-cation for a circuit breaker and additional

calibration tests per UL 508 to permit thebreaker to offer motor overload protec-tive capabilities.

The most stringent requirements (suchas electrical clearances, interruptingcapabilities, robustness, ongoingre-examination testing) are appliedto products in the energy distribu-tion category, which also includescircuit breakers. The sequence of testsconducted by UL and CSA for circuit

breakers belong to some of the mostdemanding performance requirementsfound in standards today. The line drawnbetween these various product catego-ries is also important to keep in mindwhen discussing design aspects of prod-ucts such as circuit breakers and motorcontrollers as well as understanding themanner in which these various productsare properly applied per North Americaninstallation requirements.

Certification categories per NorthAmerican standards

In North America, electrical equipmentis subject to third party certificationtesting and marking. Table 4 showsvarious certification categories whichare commonly encountered. The typeof certification ultimately impacts the

selection and manner in which the equip-ment can be applied in various end-uses.A certification report and marking is theofficial confirmation that a piece of equip-ment has met the safety, constructionand performance criteria of a given stan-dard. Many of the UL standards in theUS have been officially adopted by ANSIas American National Standards.

Eaton chooses to certify its equipmentwith UL in the US, and CSA in Canada.Along with certification, proper under-

standing of the regulations is consideredkey since most of the equipment will beinstalled in North America. The certifica-tion process can also be accomplishedthrough their international agencies and,theoretically, with competitive agenciesas well. It’s also possible for UL and CSAto certify equipment for both countries.

In the US, differentiation is madebetween equipment that is fully ULlisted, and can be field installed, versus

UL recognized, which is considered tobe incomplete and subject to additionalapplication related contingencies beforeit can be deemed to be acceptable inan end-use product or assembly. Thistype of certification can be encounteredin both energy distribution (such ascircuit breakers per UL 489 [1]) as wellas industrial control (per UL 508 [2] / UL 60947) equipment. The certificationmarks for both categories are different.As mentioned, „listed“ equipment (Partnumber suffix „-NA“ on Eaton circuitbreakers and switches) is not subjectto any particular application restrictions,whereas „recognized“ (Part numbersuffix „-CNA“ ) would involve satisfyingadditional acceptability conditions, suchas combining the product with additionalcomponents, before it could be deemedsuitable for application per the NorthAmerican electrical installation codes.

The certification agency places higherdemands on the proper selection ofrecognized components, and how thesemay need to combined with additionalequipment in order to complete anend-use product, normally assembledin a certified manufacturing location.Certified manufacturing locations aresubject to regular field inspectionsthrough agency follow-up service activi-ties (Follow-up-Service ). Certificationreports (Procedures ) in these locations

become an integral part of the manufac-turing process and describe the essentialmarking and constructional aspects ofthe certified product or assembly. Thecertified manufacturing location is theonly production facility able to assembleand label certified equipment. Productswhich are listed have been suitablyevaluated for field wiring and could bedirectly installed by an end-user.

Eaton Type suffixadded to the partnumber

Type of certification Certification marks

USA„Listing“

Canada„Certifcation Marks“

-NA The device is fully UL listed or CSA certified asa stand-alone component, and suitable for fieldinstallation.

®

„Component Recognition“

-CNA The device is component recognized by UL, not fieldinstallable, and its proper application is subject toconditions of acceptability. (Table 5)The device is CSA certified as a component but mayalso be subject to specific application conditions.

(application of the mark isoptional)

®

Table 4: Commonly encountered certification variations and corresponding agency marks, as well as suffixes used in Eaton part numbernomenclature. The yellow shaded areas refer to unrestricted application for components so marked, whereas the blue coloring deno-tes certification marks and suffixes for which specific conditions of acceptability would apply. Refer to Table 5 in this respect for moredetailed info on the significance of the respective marks in the US.


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The situation in Canada and CSA, withrespect to products with conditionalapplication capabilities, is very similar,although not as readily discernablethrough the use of marks as is the casewith UL. CSA has begun, relativelyrecently, to introduce a small yellowtriangle mark as a means to alert inspec-tion authorities to products which havedemonstrated a history of mis-applicationper the local electrical codes.

As a general rule, the paper will oftenmake sole reference to the UL standardswhen discussing a topic. This is donestrictly for brevity purposes. CSA doeshave a number of product standardscomparable to UL standards, as refer-enced in Table 3 (Page 8), and which areapplicable for CSA product certificationin Canada. Certain differences do existbetween comparable UL- and CSA-

Standards, but these will be mentionedwhenever they are relevant to the topicat hand. Figure 2 also shows additionalmarks available from UL and CSA butcurrently, Eaton only makes limited useof these more specialized certifications.

Note: A full UL listing or CSA certifica-tion for a product does not neces-sarily mean that the product can be

applied in the same manner, or withthe same performance capabilities, asis the case in the IEC world. A listedproduct does not have the same typeof restrictions applicable to Recognizedcomponents (as highlighted in Table5) but it must still be applied in accor-dance with the intent of its certificationper the North American standards andelectrical installation codes. In addition,the electrical ratings which have been

established for the product during thecertification process will need to berelevant to the manner in which theproduct is applied (energy distributionor machine control, individual motorstarters, elevator controls etc.). Theappearance of a listing or certificationmark alone does not always guar-antee that the product will be suitablefor the requirement. It is simply animportant step in establishing a basisfor the approval mandated in the NECand CEC electrical codes. Compliancewith the requirements of the electricalcodes is ultimately the decision of localauthorities having jurisdiction (electricalinspectors). In certain jurisdictions, andsome large cities (City Codes) , locallyadopted amendments to these codescould also be a factor in determiningthe overall approval of the equipment.

As shown in Tables 6 and 7, Eatoncircuit breakers type NZM..-...-(C)NAare offered under three various typesof certification. The third is somewhatof a departure from the norm in thatthe circuit breaker (Switch style E ➞ NZM..-ME..-NA) is certified as a listedproduct under UL 489, and as such, canbe applied as a normal feeder and branchprotective switch, but it also has beenadditionally evaluated under the UL 508standard as a motor overload protective

device. When it is applied in this manner,i.e. as part of a combination motor starterin branch circuits, it is typically combinedwith a listed motor contactor. Pleaserefer to the Eaton Main Catalog underthe “Circuit Breaker” chapter for addi-tional information on permissible motorstarter combinations using this circuitbreaker.

Figure 2: Additional UL and CSA certification marks available for producers. Currently,Eaton only makes limited use of a portion of these more specialized marks. The marksfrom ETL-Intertek represent yet another Nationally Recognized Testing Laboratory inNorth America, under which components and assemblies could be certified. The additi-onal letters “C” and “US” seen to the left and right of each agency’s respective certifica-tion marks signify conformity with Canadian and/or US safety requirements respectively.

Listed equipment Component Recognized Equipment

No restrictions when applied per their certification Application based on conditions of acceptability

• Devices listed for „field wiring“• „factory wiring“ is covered by „field wiring“ provisions

• As components, products are suitable for „factory wiring“only.

– Listed devices are suitable for control panels when used perthe guidelines of the industrial control panel standard (UL508A).

– Listed devices are not subject to additional conditions ofacceptability.

– Components are considered incomplete and could requirecombinations with other equipment in end-use assemblies

– Component selection is conducted by trained personnel andsubject to Conditions of Acceptability

– For use in control panels; designed, wired and tested bytechnically trained personnel in certified factories and panelshops.

Certification Mark: Certification Mark:

Table 5: In the US differentiation is made between UL „listed“ and „recognized“ equipment. CSA does not differentiate certified equip-ment in the same manner.


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Interaction of panel builders and usersof certified components

In Europe there are a number of so-calledinstallation standards, e.g. IEC/EN 60204-1 [7] (Electrical apparatus for indus-trial machinery) which contain require-ments for particular applications that gobeyond what an equipment manufactureralone can provide in terms of conformity.Responsibility for full compliance isalso shared by project engineers, panelbuilders, contractors and/or end-users

alike.

A similar situation also exists in NorthAmerica with respect to compliancewith the regulations. A circuit breaker,as a stand-alone component, is normallyUL listed and CSA certified. That iscertainly an important element, but notnecessarily the only prerequisite whichguarantees a compliant assembly perNorth American requirements. Circuitbreakers, like those used in motorstarter branch circuits, need to be addi-

tionally evaluated with motor startercomponents as complete and stand-alone assemblies (combination motorcontrollers). The combination ratingsare then documented in certificationreports and can be used to establish

optimal ratings for the assemblies intowhich they are installed. An exampleof that would be short circuit currentrating (SCCR) requirements for industrialcontrol panels per the NEC and UL 508Astandard. This requirement almost nulli-fies the practice of combining compo-nents from various manufacturers whichhave not been tested as an assembly,since the overall rating of the panelalways defaults to the power devicewith the lowest rating. A drastic reduc-tion in the overall short circuit rating of

a panel could thus ensue, and lead topotential safety and approval problemsif the suitability of the panel cannot beresolved with the prevalent circuit condi-tions at the installation site.

A panel builder can also obtain infor-mation on certified short circuit ratedcombination motor starters from variousmakes directly from UL’s on-line resourceof information on UL 508A industrialcontrol panel assemblies (http://www.ul.com/controlequipment/shortcircuit.

html). Another easy method is to consultindividual manufacturer catalogs. ForEaton, that would be the Main Cata-logue „Industrial switchgear products“,which contains relevant certificationdata directly on the component selec-

tion pages. Additional information can beobtained from the Eaton web site (http:// www.eaton.com/moellerproducts).

Equipment certification is always anongoing process so it’s always advisableto keep in touch with Eaton sales engi-neers for the latest news. They wouldhave access to the most recent updateswith respect to product introductions,as well as the latest developments onthe standards front to benefit applica-tion related solutions for equipment

and assemblies. This is especially truefor Eaton’s line of molded case circuitbreakers presented here, since newlyupdated ratings and adaptations to theproduct line resulting from changes inthe standards can also occur from timeto time.

Eaton offers a comprehensive array ofaccessories for its breaker line, includingvarious operators that are customized forparticular applications. The requirementsfrom the industrial machinery standard

NFPA 79, and UL 508A, are especiallynoteworthy in this respect. It’s importantto re-state that a product certificationalone is not sufficient. The equipmentmust also meet the installation guidelinesof the electrical codes (NEC and CEC).

Type of certification and application possibilites for UL 489 and UL 508 equipment

Switchstyle

Type Typesuffix

Switch Test stan-dard certifi-cation

Additional evaluation Special acceptabilityconditions per UL 508

A NS..-...-NA -NA Molded CaseSwitch*

UL 489 - -

B.1 NZM..-S..-CNA -CNA Instantaneous TripCircuit Breaker UL 489 -Use together withadditional contactor and

overload relay**B.2 NZM..-SE..-CNA -CNA UL 489 -

C.1 NZM..-AF..-NA -NA Inverse Time CircuitBreaker

UL 489 - -

C.2 NZM..-AEF..-NA -NA UL 489 - -

C.3 NZM..-VEF..-NA -NA UL 489 - -

D.1 NZM..-A..-NA -NA Inverse Time CircuitBreaker

UL 489 - -

D.2 NZM..-AE..-NA -NA UL 489 - -

D.3 NZM..-VE..-NA -NA UL 489 - -

E NZM..-ME..-NA -NA Motor ProtectiveCircuit Breaker

UL 489 Calibration test perUL 508 for motoroverload protectioncertification

Typically combined with

contactor for motor branch

circuits.***

Type suffix indicates certification -NA = Listed component - CNA = Recognized component* Molded case switches have an integrated trip mechanism for self-protection.** The instantaneous trip breaker, contactor and overload relay are part of a listed combination motor controller*** The breaker is part of a listed combination motor controller with Eaton contactors

Application possibilites: As a UL 508 combination starter As per UL 489 and UL 508

Table 6: Application possibilities for UL 489 and/or UL 508 certified equipment per the North American electrical codes. Certain condi-tions of acceptability may apply.


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Table 7: Variations in certification categories and application possibilities. Both certification categories on the left hand side of the Tablewould allow for protection of cables and systems. As described in this paper, such breakers could also be used for generator protectionand be suitable for selectivity functions in energy distribution networks.

– Circuit Breakers- Variations per application and type of certification –

Suffix „-NA“

„Listed equipment“

Full UL 489 Certification

X Examples:

C.1 NZM..-AF..-NA

C.2 NZM..-AEF..-NA

C.3 NZM..-VEF..-NA

Note that the suffix „-NA“

can have subtle differences

Suffix „-NA“

X „Listed equipment“,because:

X Stand-alone UL 489 -Certification

X Additional evaluation: UL

508 – Calibration testing

Example:

E NZM..-ME..-NA

Suffix „-CNA“

“Recognized Components“

Full UL 489 Certification

X Example:

B.1 NZM..-S..-CNA

B.2 NZM..-SE..-CNA

For application as InverseTime Circuit Breakers(for non-motor loads)

Stand-aloneUL 489 - Certification

For application as a MotorProtective Circuit Breaker

(for motor protection)

Additional evaluation:UL 508 - Calibration

Be aware of generalapplication restrictions

associated to „RecognizedComponents“

Additional acceptabilitycondition: Combination with

contactors and overloadrelays in a listed assembly

Additional acceptabilitycondition: Combination withcontactors for typical motor

starter appications

N e w

C e r t i f i c a t i o

n t y p e s

Overview of the North Americanproduct line: Molded Case CircuitBreakers, Switch-Disconnectors andMolded Case Switches

As in North America, the rest of theworld refers to the type of productcovered in this paper under the generalheading of “Molded Case Circuit

Breakers ”, primarily for their unitiziedand enclosed construction, as wellas their compact design. (Photo 3).In the US and Canada, depending on


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17

12

12

13

68

75

23

22

14

11

18

16

20

19

21

15

9

10

1

4

2

3

1 Circuit Breaker orMolded Case Switch

2 IP2X Finger protection3 Terminal cover,

with knockout segments4 Cover5 IP2X Finger protection for cover6 Barrel type termination lugs7 Box type termination lugs8 Control circuit terminations9 Component busbar adapters10 Clip plate11 Spacer

12 Single or double auxiliary contacts

13 Rear operation mechanism14 Sidewall drive mechanism15 Supplementary handle for NA16 Extension shaft with door

handle coupler17 Door mounted rotary handle18 Switch mounted rotary handle19 Identification label20 Cutout frame21 Remote control drive22 Vertical motion handle for NA23 Undervoltage and shunt trips

Figure 3: Pictorial overview of the compact molded case circuit breaker line, types NZM1 through NZM4. The range also includes Mol-ded Case Switches, types NS1 through NS4. The diagram shows the essential elements which make up this universally applicablecircuit breaker product range. The North American versions feature a 3 pole construction (for 4 pole NA versions, refer to Table 13c),whereas the IEC portion of the line includes 4 pole models as standard, in order to fully accommodate all supply network requirementsfor that market. Plug-in and withdrawable units are not certified for use on the North American market.


14/6414

the type of trips they contain, they arealso often referred to as „Inverse TimeCircuit Breakers ” (i.e. circuit breakerswhose trip response times are inverselyproportional to the magnitude of the faultcurrent) or „Instantaneous Trip CircuitBreakers “ (circuit breakers without anyoverload trip function, commonly foundin motor starter circuits.) There are note-worthy differences in the constructionalapproach of non-automatic switches(switches with no protective functions),in particular between the Type N, IECstyle “Switch-Disconnectors”, and UL/ CSA certified type NS Molded CaseSwitches , which the paper will describein more detail in a separate chapter.

Table 8 shows the line-up of NZM 1,NZM 2 , NZM 3 und NZM 4 circuitbreakers along with certified currentratings for each respective frame size.

The Table also differentiates betweenbreakers with conventional electro-mechanical trips versus those with elec-tronic tripping means. Circuit breakers

with full inverse time tripping capabili-ties can be used for cable and systemsprotection. The following breakdownsapply:• Switch style B – Circuit breakers

without overload trips• Switch style C – Circuit breakers with

fixed overload trips and• Switch style D – Circuit breakers with

adjustable overload trips

Switch style B (NZM..- S ..-CNA, NZM..- SE -CNA) without overload trips, arevery seldom used in the IEC world, andSwitch style C (NZM..- AF ..-NA, NZM..- AEF ..-NA, NZM..- VEF ..-NA), with fixedoverload trips, are almost never encoun-tered. Table 8 also refers to a numberof circuit breaker nominal current ratingswhich are not being offered in the IECrange. Although production volumes forEaton’s IEC devices outnumber the quan-

tities of product manufactured for theNorth American market, the assortmentselection of UL/CSA certified devices isquite a bit more diverse.

Each additional version can trigger addi-tional costs, e.g. for the global logisticalpicture, and can complicate planningfrom the user’s point of view, sincethere are more types to deal with andpotentially more inventories to carry. Thevariety in North American product offer-ings is certainly justified from an applica-tion point of view, even though the restof the IEC world seems to get by fineand without being unduly restricted bythe lesser amount of variety. On theother hand, the North American market,and especially the indirect export busi-ness originating from the EU, is so stra-tegically important that Eaton fully justi-fies the need to offer a more completeline and cater to the special requirementsof that market. The paper should helpclarify the assortment of models andsimplify the selection process.

Table 9 follows by providing additionalinformation on breakers with undelayedand delayed short circuit trips. Switchstyles B, C and D are further differenti-

Rated nominal currents In of North American molded case circuit breaker versions

Suitable for systems- and cable protection, 3 pole, with short circuit trips (“-NA” versions only, with overload trips). Certi-fied per UL 489 and CSA -C22.2 No. 5-09

Breakers with thermal-magnetic trips

Without overload tripsFor these switch types, I u relatesonly to the adjustable instanta-neous trip setting rangesI n = I u [A]

Fixedoverload trip settings

I n = I u [A]

Adjustableoverload trip settings

I n = I u [A]

Adjustable over-

load trip setting

ranges I r

NZM 1 ...- (C)NA 1.2, 2, 3, 5, 8, 12, 18, 26, 33, 40,50, 63, 80, 100

20, 25, 30, 35, 40, 45,50, 60, 70, 80, 90, 100,110, 125

20, 25, 32, 40, 50, 63,80, 100, 125

0,8 ... 1 x I u

NZM 2 ...-(C)NA 1.6, 2.4, 5, 8, 12, 18, 26, 33, 40,50, 63, 80, 100, 125, 160, 200,250

15, 20, 25, 30, 35, 40,45, 50, 60, 70, 80, 90,100, 110, 125, 150, 175200, 225, 250

20, 25, 32, 40, 50, 63,80, 100, 125,160, 200,250

0,8 ... 1 x I u

Breakers with electronic tripsWithout overload tripsFor these switch types, I u relatesonly to the adjustable instanta-neous trip setting rangesI n = I u [A]

Fixedoverload trip settings

I n = I u [A]

Adjustableoverload trip settings

I n = I u [A]

Adjustable over-

load trip setting

ranges I r

NZM 2 ...-(C)NA 90, 140, 220 150, 175, 200, 225, 250 100, 160, 250 0,5 ... 1 x I u

NZM 3 ...-(C)NA 220, 350, 450 250, 300, 350, 400,450, 500, 550, 600

250, 400, 600 0,5 ... 1 x I u

NZM 4 ...-NA - 600, 700, 800, 900,1000, 1200

800, 1000, 1200 0,5 ... 1 x I u

Switch type: Style B Style C Style D

Table 8: UL 489 and CSA -C22.2 No. 5-09 certified molded case circuit breakers for the North American market are offered in a third vari-ation consisting of fixed overload or long time response trip settings. „NA“ switches, which are also in conformity with IEC standards,also bear ratings in accordance with the relevant IEC/EN 60947 component standard. This greatly simplifies the export from NorthAmerica into the IEC world.


15/6415

ated in B.1, B.2, C.1, C.2, C.3, D.1, D.2and D.3 variations.

Table 9 also provides more details on the

line of switch-disconnectors/molded case

switches, Switch style A (NS ..- ..-NA). All

Eaton circuit breakers and switches fulfillthe requirements the IEC/EN 60 947-3 [11]

standard for switch and load disconnec-

tors, in addition to all applicable portions of

the basic circuit breaker product norm IEC/

EN 60 947-2 [10]. Table 9 (page 16) also

includes application related information for

the products shown.

UL 489 listed and CSA-C22.2 No. 5-09certified circuit breakers shown in Table9 meet the constructional (large elec-

trical clearances) and interrupting ratingrequirements of distribution equipmentand can be used as protective switchesin those assemblies (typically switchboards, panelboards, busways etc…,).In addition, Switch style E (NZM..- ME ..-

NA) , has been additionally evaluated perUL 508 and CSA-C22.2 No. 14 to providethe motor overload protective capabilityin motor branch circuits. The Table doesnot include information on the necessityof additional power circuit components

required for certain applications. (to beelaborated on later in the paper).

Various interrupting rating levels avail-able for North American breakers furtherexpand the line, just as is the case with

240 V 60 Hz Rated current I n [A]

2 0

. . .

5 0

1 2 5

. . .

. . .

2 5 0

3 0 0

3 5 0

4 0 0

4 5 0

5 0 0

5 5 0

6 0 0

7 0 0

8 0 0

9 0 0

1 0 0 0

1 2 0 0

Basic 35 kA

35 kA

NZM B1

NZM B2

Normal 85 kA

85 kA

NZM N1

NZM N2 NZM N3 NZM N4 High 125 kA

150 kA

200 kA

NZM H4

NZM H2 NZM H3

NZM H2 1)

480 Y/277 V 60 Hz

Basic 25 kA

25 kA

NZM B1

NZM B2

Normal 35 kA

35 kA

42 kA

NZM N1

NZM N2

NZM N3 NZM N4

High 85 kA

100 kA

150 kA

NZM H4

NZM H2 NZM H3

NZM H2 1)

480 V 60 Hz

Basic 25 kA NZM B2

Normal 35 kA

42 kA

NZM N2

NZM N3 NZM N4

High 85 kA

100 kA

150 kA

NZM H4

NZM H2 NZM H3

NZM H2 1)

600 Y / 347 V 60 Hz

Basic 18 kA NZM B2

Normal 25 kA

35 kA

NZM N2

NZM N3 NZM N4

High 50 kA

65 kA

NZM H2 NZM H3 NZM H4

NZM H2 1)

600 V 60 Hz

Normal 35 kA NZM N3 NZM N4

High 50 kA NZM H3 NZM H4

1) NZMH2-A15-NA ... NZMH2-A125-NA, NZMH2-AF15-NA ... NZMH2-AF125-NA

Figure 4: Interrupting capacity of various circuit breaker frame sizes at standard North American supply voltage ratings and per UL andCSA (NEMA) test procedures. The values correspond to the assigned Short Circuit Current Ratings (SCCR) of individual breakers.


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IEC rated devices. Interrupting rating

refers to the highest current rating atrated voltage that the breaker is ableto clear under short circuit conditions.Interrupting level capabilities are deter-mined to a large extent by constructionalfeatures of the design, and will alsoinfluence price levels. Different levelsof interrupting capability will provide thepanel builder with additional flexibility inmatching the breaker to the technicalrequirements of the application as wellas help keep pricing better in line withthe need. Interrupting ratings for North

America and the IEC world are doneper different standards and at differentvoltage levels. Thus the differences seenin values attained for both markets.

Table 10 presents the interrupting levelsof the breaker line for both IEC and NorthAmerican markets. Interrupting ratingsare always a function of the distributionvoltage level at which they are deter-mined. This relationship is highlighted in Figure 4 for the North American values.The interrupting rating of the breaker

corresponds to its short circuit currentrating (SCCR). The SCCR values for thecombination of a breaker and an addi-tional power circuit component, such asa contactor, can be higher simply dueto the additional sets of contacts in the

circuit which can contribute to help clear

a fault.

Table 11 presents the rating data for thenew, North American style molded caseswitches (Switch syle A) (NS..-..-NA)(refer also to chapter „Switch-discon-nector N or Molded Case Switches NS “). Table 12 is more or less a compilation ofthe information from tables 8 through11 (8: page 14, 9: page 16, 10: page 17,11: page 18) with specific reference tonominal current ratings.

“Typical North American” circuitbreakers in energy distribution circuits

• for non-motor loads

„Typical North American“ circuitbreakers for energy distribution circuitshave either fixed overload and fixedinstantaneous thermal-magnetic tripsystems, fixed overload and adjustableinstantaneous thermal-magnetic tripsystems, or adjustable electronic trip

systems. Circuit breakers of this varietyare fully listed per UL 489 or certifiedper CSA-C22.2 No. 5-09, and typicallyprovide both overload and instantaneousshort circuit protection of non-motorcircuits. Eaton also offers a fixed over-

load electronic trip response breaker for

the North american market.

The fixed overload trip response versionsare offered under the part numbersNZM...AF..-NA (thermal-magnetic)und NZM... AEF..-NA (electronic) .Breakers with fixed overload trips are notcommonly used in the IEC world. Thisversion appears in the tables throughoutthe paper as Switch styles C.1 and C.2A third version of this variety, Switchstyle C.3 (NZM..- VEF ..-NA) featuresadditional short circuit trip responses to

make them more suitable in circuits withselective co-ordination.

Circuit breakers with fixed overload tripresponses can be found in energy distri-bution assemblies as either incoming oroutgoing protective switches in feederand branch circuits. As circuit breakers,they also fulfill the function of a maindisconnect switch per the electricalcodes. They are also commonly used asalternatives to fuses in the protectionof industrial control equipment falling

under the North American UL 508 andCSA-C22.2 No.14 product standardsand as protective switches in industrialcontrol assemblies such as IndustrialControl Panels and Motor ControlCenters. They provide feeder protection

Selection criteria for molded case circuit breakers and switches for the North American market.

Style Type Certificationfor the US

Certification forCanada

Additional application relatedevaluations for the US andCanada

Overload pro-tection

Short Circuit protectionundelayed delayed

A NS..-...-NA UL 489 CSA-C22.2 No 5-09 - - Internallyself-pro-tected

-

B.1 NZM..-S..-CNA UL 489 CSA-C22.2 No 5-09 - - EM -

B.2 NZM..-SE..-CNA UL 489 CSA-C22.2 No 5-09 - - EL -

C.1 NZM..-AF..-NA UL 489 CSA-C22.2 No 5-09 - EM, fixed EM -

C.2 NZM..-AEF..-NA UL 489 CSA-C22.2 No 5-09 - EL, fixed EL -

C.3 NZM..-VEF..-NA UL 489 CSA-C22.2 No 5-09 - EL, fixed EL EL

D.1 NZM..-A..-NA UL 489 CSA-C22.2 No 5-09 - EM, adjustable EM -

D.2 NZM..-AE..-NA UL 489 CSA-C22.2 No 5-09 - EL, adjustable EL -

D.3 NZM..-VE..-NA UL 489 CSA-C22.2 No 5-09 - EL, adjustable EL EL

E NZM..-ME..-NA UL 489 CSA-C22.2 No 5-09 Calibration test per UL 508 andCSA-C22.2 No.14

EL, adjustable EL -

EM = Electro-Magnetic EL = Electronic

Table 9: Various differences in Eaton circuit breaker and switch offerings for the North American market with respect to design, type ofcertification and range of application. All switch variations are suitable for energy distribution systems, with the exception of Instantane-ous-only circuit breaker styles B.1 and B.2 which are for individual motor circuits only. Switch style „E“ are suitable for motor circuits aswell, and are typically combined with a motor contactor for combination motor controller branch circuit application purposes.


17/6417

as well as branch circuit protection forvarious loads. (Figure 5) [12].

• Motor loads

North Americans use fixed trip circuitbreakers fairly commonly. Because thebreaker fixed overload trip response2 is not calibrated for overload protec-tion, there is a need to add a separatemotor overload relay, along with a motorcontactor, to form the basis for a combi-nation motor starter (UL/CSA Construc- tion Type C, Combination Motor Starters)The fixed trip breaker provides conductoroverload and short circuit protectionwhereas the separately mounted over-load relay provides the motor overload

2 UL 489 certified circuit breakers in the US,whether equipped with fixed or adjustable longtime (overload) response trips, are considered

the same. The adjustable overload trip feature ofa breaker does not necessarily offer a protectiveadvantage. Both types are not consideredsuitable as stand-alone devices for the overloadprotection of motors

Main application Supplementary applications

Molded Case Switch Main and Emergency-OFF disconnect

Short circuit protection Main and Emergency-OFF disconnect, forindividual motor starters only

Short circuit protection Main and Emergency-OFF disconnect, forindividual motor starters only

Cable and systems protection Main and Emergency-OFF disconnect


Cable, systems and generator protection,selectivity

Main and Emergency-OFF disconnect



Cable, systems and generator protection,selectivity Main and Emergency-OFF disconnect

Cable and systems protection, motor protection Main and Emergency-OFF disconnect

Molded Case Circuit Breakers for North AmericaShort circuit interrupting ratings per UL/CSA/NEMA and IEC test procedures

UL / CSA / NEMA Test Procedure Breaking capacity I cu per IEC 60 947

SwitchType

240 V60 Hzsym. rms[kA]

480 Y/277 V60 Hzsym. rms[kA]


600 Y / 347 V60 Hzsym. rms[kA]


400/415 V50/60 Hz

[kA] / cos

440 V50/60 Hz

[kA] / cos

690 V50/60 Hz

[kA] / cos

Basic InterruptingRating B

NZMB1-...-NA 35 25 - - - 25 / 0.25 25 / 0.25 -

NZMB2-...-NA 35 25 25 18 - 25 / 0.25 25 / 0.25 -

Normal Interrupt-ing Rating N

NZMN1-...-NA 85 35 - - - 50 / 0.25 35 / 0.25 10 / 0.50

NZMN2-...-NA 85 35 35 25 - 50 / 0.25 35 / 0.25 20 / 0.30

NZMN2-...E...-NA 85 35 35 25 - 50 / 0.25 35 / 0.25 20 / 0.30NZMN3-...E...-NA 85 42 42 35 35 50 / 0.25 35 / 0.25 20 / 0.30

NZMN4-...E...-NA 85 42 42 35 35 50 / 0.25 35 / 0.25 20 / 0.30

High InterruptingRating H

NZMH2-...-NA 150 100 100 50 - 150 / 0.20 130 / 0.20 20 / 0.30

NZMH2-A…-NA1) 200 150 150 65 - 150 / 0.20 130 / 0.20 20 / 0.30

NZMH2-AF…-NA1) 200 150 150 65 - 150 / 0.20 130 / 0.20 20 / 0.30

NZMH2-...E...-NA 150 100 100 50 - 150 / 0.20 130 / 0.20 20 / 0.30

NZMH3-...E...-NA 150 100 100 50 50 150 / 0.20 130 / 0.20 35 / 0.30

NZMH4-...E...-NA 125 100 100 50 50 150 / 0.20 130 / 0.20 50 / 0.25

Ratings in the latest main catalog are binding! 1) NZMH2-A15-NA through NZMH2-A125-NA and NZMH2-AF15-NA through NZMH2-AF125-NA

Table 10: Comparison of short circuit interrupting ratings of various molded case circuit breaker frame sizes and switch types per com-parable North American and IEC circuit breaker standards. The North American ratings are not identical to the IEC ratings. Breakerswith 480Y/277VAC and 600Y/347V slash voltage ratings are suitable for installations in solidly grounded wye networks only. The shortcircuit interrupting ratings of each circuit breaker type corresponds to the device’s overall short circuit current rating (SCCR). Shortcircuit ratings of instantaneous trip circuit breakers (without overload trips) are assigned only to the overall combination of a breaker,contactor and overload relay in a listed combination motor controller assembly.


18/6418

protection with trip responses not

exceeding those mandated by the elec-trical codes (certain correction factorsmay also apply). This type of solution,i.e. with 2 overload protective devices inthe circuit, would be difficult to defend inthe IEC world from both an economicalviewpoint, as well as from a technicalperspective in view of the supplementaryheat losses provided by the additionalcomponent. Furthermore, the requiredspace for the starter is greater, as well asthe assembly and wiring time. The solu-tion does not lend itself well for export

purposes in applications with motor

currents up to 200A. Above 200A, a 3component solution featuring a fixed tripinverse time breaker may be more justifi-able technically.

Eaton offers the fixed trip breakersper Table 12 in current ranges from20A through 1200A, and at various

short circuit interrupting rating levels

commonly encountered in NorthAmerica. Tables 13a, 13b and 13c, resp.14 show all available variations of thesebreakers. They are selected per theirnominal current and interrupting rating. Ifthey are equipped with auxiliary contacts,appropriate rating data (such as PilotDuty [3]) is also provided on the breaker.

Figure 5: There is a differentiation madein North America between Feeder Circuitsand Branch Circuits. The Figure shows aportion of the electrical controls for anindustrial machine assembly (IndustrialControl Panel for Machinery). The bestway to properly assess the line betweenboth circuits is to look at it from the loadside, back towards the power source. Thebranch circuit terminates at the protectivedevice, which is appropriately referred toas the Branch Circuit Protective Device(BCPD). Branch Circuit Protective Devices

consist mostly of molded case case circuitbreakers and fuses, but in certain cases,like individual motor circuits for example,the branch circuit protective functioncould be fulfilled by a UL 508 Type E Self-Protected combination motor controller, ora Type F combination motor controller.

Main distributionsystem

or

or

Incoming side Industrial control panel

Busbar system Busbar system

Feeder CircuitsLarge creepage andclearance distances

Main switch

Branch CircuitProtectiveDevice

Branch Circuits Small creepage and clearancedistances

Load side

Branch CircuitProtective Device

The Branch Circuit endsat the Branch CircuitProtective Device BCPD

(viewed from the load side)

The Feeder Circuit includes allelements upstream of the BCPD ,as well as the incoming supplyterminals of the BCPD (viewedfrom the load side)

Switch-Disconnectors for North AmericaSwitch-Disconnectors for North America with internal self-protective tripsMolded Case SwitchesCertified per UL 489 and CSA-C22.2 No. 5-09

Nominal current =Rated continuouscurrent

I n = I u [A]

Switch internally self-protects up to its maximum rated shortcircuit rating

Internal self-protectiveinstantaneous tripresponse current

[A]

Type

SCCR *

240 V[kA] 480 Y / 277 V[kA] 480 V[kA] 600 Y / 347 V[kA] 600 V[kA]

63 85 35 - - - 1250 NS1-63-NA

100 85 35 - - - 1250 NS1-100-NA

125 85 35 - - - 1250 NS1-125-NA

160 150 100 100 50 - 2500 NS2-160-NA

200 150 100 100 50 - 2500 NS2-200-NA

250 150 100 100 50 - 2500 NS2-250-NA

400 150 100 100 50 50 6600 NS3-400-NA

600 150 100 100 50 50 6600 NS3-600-NA

800 85 65 65 42 42 25000 NS4-800-NA1000 85 65 65 42 42 25000 NS4-1000-NA

1200 85 65 65 42 42 25000 NS4-1200-NA

Ratings in the latest main catalog are binding! * SCCR = Short Circuit Current Rating per UL 508A

Table 11: North American molded case switches per UL 489 and CSA-C22.2 No. 5-09 have an internal instantaneous trip for self-protection.This is the most commonly encountered design in North America for these switch types. They can be equipped with undervoltage orshunt trips accessories to help trip them open electrically from a remote location. Molded case switches are used mainly as supply circuitand emergency-off disconnect switches. Type NS2-…-BT-NA switches are available with factory supplied line and load box terminals. TypeNS1-...-NA switches come standard with line and load box terminals.

Switch style A


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Circuit breakers with adjustableoverload trips

In addition to fixed overload trip responsebreakers, a variation with adjustableoverload trips (as is typical in the IECworld), is offered as an alternative. Thesebreakers are similarly listed and certifiedin North America as protective switchesfor cable and systems. They are refer-enced in the paper as Switch style D.1(NZM..- A..-NA) and D.2 (NZM..- AE ..- NA) (Tables 15 and 16). These circuitbreakers are also not suitable for motoroverload protection since they havenot been additionally evaluated per UL508 for that capability. Switch styleD.3 (NZM..- VE ..-NA), have additionaltrip response functions that make themideally suited per Table 9 (page 16) forapplications like generators, transformersand circuits with selective co-ordination.

(refer to chapter „Circuit breakers forspecial applications on the NorthAmerican market“ )

Motor protection/Systems protection

Eaton refers to its PKZM... compact lineof circuit protective devices for currentsup to 65A as „Motor Circuit Protectors“.These motor protective devices havea built-in single phasing differential tripfeature in compliance with the IEC/EN

60947-4-1 standard. This single phasingsensitivity can be a problem when thedevices are used as protective switchesin non-motor load circuits, because anasymmetrical loading of phases, whichcan commonly occur in such circuitswhen phases are being individuallytapped, could cause nuisance tripping.For this reason, Eaton offers so-called“systems protection” devices in thatproduct line, e.g. PKZ2 switches which,as is typical of circuit breakers, do notcarry that feature. The special motor

protective circuit breakers discussedand presented in this paper, however, dohave a built-in characteristic feature thatmakes them sensitive to single phasingconditions in motor circuits.

Additional requirements for circuitbreakers in motor protectiveapplications

Without the addition of a contactor andoverload relay, the afore-mentioned certi-

fied circuit breaker types NZM...A(E) F..-NA (Switch style C.1 and C.2) areused primarily as protective devicesin feeder and non-motor load branchcircuits. These breakers are not asreadily suited for direct motor overload

protective functions since they have afixed setting and cannot be set exactly tothe motor full load current. Furthermore,their overload trip function has not beenadditionally evaluated for protection ofmotors. Independent of the overload tripadjustability factor, there is somewhatof a parallel between North Americanand IEC standards as it relates to motorprotection, since there would also be aneed in the IEC world to pull in perfor-mance requirements from additionalstandards in order to verify the capabilityof a circuit breaker for the application.The circuit breaker standard IEC/EN 60947-2 [10] alone does not include anyprovisions to verify a breaker’s suitabilityfor motor overload protection. Thus, inthe IEC world, specific requirementsfrom the motor starter standard IEC/ EN60 947-4-1 [13] would need to be intro-duced for this purpose. That standard

specifically describes actual trip curvecalibration requirements for motor over-load protection, which are not addressedin the circuit breaker standard, and alsospecifies trip class designations. Theoptional inclusion of the differentialsingle phasing sensitivity protectionfunction is also part of the IEC/EN 60947-4-1 motor starter standard. Thestandard further includes provisions forverifying „Type 1“ and „Type 2“ protec-tion co-ordination values for combinationmotor starters. These same co-ordination

values have also now been incorporatedinto the newly introduced UL 60947 [14]standard as part of the ongoing harmoni-zation effort. Although not part of NorthAmerican standards up to that point,Type 2 co-ordination taken from the IECstandard had been the focus of specialrequests made to electrical equipmentmanufacturers by large North Americanfirms as a way to improve motor starterprotection levels in their own facilities.Testing agencies in North America, suchas UL, had been able to accommodate

requests for third party verificationof these starters solely through theirclassification program, which usuallyinvolved the issuance of a letter reportas opposed to a listing mark. With theintroduction of the UL 60947 standard,UL will now be able to grant the morepreferred listing mark for such assem-blies. Single phasing sensitivity per theIEC definition has also been increasinglyrequested in motor protective compo-nent specifications by large end-users.

In order to be performance verified forthe direct overload protection of motors,circuit breakers in North America mustfirst be fully certified as stand-alonecircuit breakers per the relevant productstandards (such as UL 489) and then be

additionally evaluated per the calibrationrequirements of the industrial controlstandard (such as UL 508 and CSA-C22.2No.14). Per these North Americanstandards a 3 phase overlod protec-tive device (such as the one discussedhere) would have to demonstrate,among other tests, acceptable trippingresponses when loaded on 2 phasesat 600% and 200% of a given motorload current. This test is very broadlycomparable to the IEC single phasingsensitivity verification. North Americancalibration tests also involve differentia-tion between various trip classes (Class10, 20 or 30).

Note: Consideration must be made forthe fact that, at higher trip classes, alarger current will be expected to flowfor a longer time. This will produce

greater thermal stresses for the entirecircuit, including cables and switchingdevices, which need to be sized for theincreased burden accordingly.

In the IEC world, circuit breakers withmotor protective and (IEC) switchingcapabilities are deemed suitable foroccasional and intentional switching ofmotors directly on line. In North America,the electrical codes also permit this func-tion for listed and certified inverse timecircuit breakers, as well as for molded

case switches. Typically, however, circuitbreakers in North America are used withseparate components in motor branchcircuits, such as contactors and overloadrelays. And, as previously mentioned,circuit breakers that would provide themotor overload protection function mustalso be additionally evaluated for thatpurpose per the industrial control stan-dards (refer to next section).

Requirements for motor starters on

the North American market

At this point, additional information onthe topic of motor starters is presentedin order to help provide a clearer over-view. In North America, the electricalcodes require the motor branch circuit tofulfill 4 essential functions: (Figure 6)

• Isolation (Main disconnect),• Short circuit protection,• Motor switching or controller (with

controller or e.g. with motor contactor/

inverter)• Overload protection

These 4 functions can be accomplished inthe IEC world with a single circuit breakeror motor protector, assuming the equip-


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ment in question has met the additional

conformity provisions of the IEC/EN 60947-4-1 motor starter standard. The addi-tion of a contactor is made solely andfreely upon need, i.e. in cases where ahigh degree of switching frequency isrequired for the application, or longer lifefor the equipment is desired.

The electrical codes do permit the use ofa certified inverse time circuit breaker forthe controller function so that all Eatoncircuit breakers listed and certified forthe North American market (Type suffix

“-NA”) would fulfill the requirement.Typically though, the majority of circuitbreakers used in motor branch circuitsin North America are combined withcontactors and separate overload relaysand certified as complete combination

motor starter assemblies with their own

assigned short circuit rating (SCCR). As isthe case for both North America and theIEC world, the use of a separate motorcontactor for motor loads representsthe most advantageous solution in mostapplications, especially for high motorswitching frequency requirements andcertainly whenever motor starter opera-tion needs to be fully automated.

The following info applies to thesmaller frame Type PKZM motorprotectors and similar designs from

other makes, which have currentratings falling below those of theNZM 1 … NZM 4 circuit breaker line [3]:

Note: Per North American standards,

the typical European style manualmotor protector is commonly certifiedin North America as a UL 508 listed,HP rated “manual motor controller”capable of providing motor overloadprotection only. They are not recog-nized as having a stand-alone shortcircuit protective capability. Unlike theIEC world, these components requirean additional upstream protectivedevice per the electrical codes. Protec-tive devices consist of listed fusesor inverse time molded case circuit

breakers. The electrical codes allowthe possibility of grouping the control-lers under a single back-up protectivedevice if they are certified accordingly.All Eaton motor protectors fulfill this

S t y l e

T r i p

t y p e s

O v e r l o a

d

w i t h o u

t

f i x e

d

a d j u s

t a b l e

S h o r t c

i r c u

i t

u n

d e

l a y e

d

d e

l a y e

d

I n t e r r u p

t i n g

r a t i n g

N Z M

. .

– . .

Nominal rated current [A]

1 . 2

1 . 6

2 2 . 4

3 5 8 1 2

1 5

1 8

2 0

2 5

2 6

3 0

3 2

3 3

3 5

4 0

A * * 1

* * 2* * 3

* * 4

B.1 EM x x B,N 1 x - x - x x x x - x - - x - - x - x

EM x x B,N,H 2 - x - x - x x x - x - - x - - x - x

B.2 EL x x N,H 2

EL x x N,H 3

C.1 EM x x B,N 1 x x - x - - x x

EM x x B,N,H 2 x - x x - x - - x x

C.2 EL x x N,H 3

EL x x N,H 4

C.3 EL x x x N,H 2

EL x x x N,H 3

EL x x x N,H 4

D.1 EM x x B,N 1 x x - - x - - x

EM x x B,N,H 2 x x - - x - - x

D.2 EL x x N,H 3

EL x x N,H 4

D.3 EL x x x N,H 2

EL x x x N,H 3

EL x x x N,H 4

E EL x x N,H 2

Style = Switch style, refer to Table 6 (Page 11)* = Internal instantaneous trip for switch self-protectionTrip types: EM = Electro-magnetic , TM = Thermal-magnetic, EL = Electronic

= Molded case switch

Interrupting Rating:B = BasicN = NormalH = High

For specific interrupting ratings refer to Table 10 (Page 17)

Table 12: Exact correlation of breaker styles with respect to rated currents, interrupting rating levels and trip types.


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5 0

6 0

6 3

7 0

8 0

9 0

1 0 0

1 1 0

1 2 5

1 4 0

1 5 0

1 6 0

1 7 5

2 0 0

2 2 0

2 2 5

2 5 0

3 0 0

3 5 0

4 0 0

4 5 0

5 0 0

5 5 0

6 0 0

7 0 0

8 0 0

9 0 0

1 0 0 0

1 2 0 0

x - - - x - x

x - x - - xx - - - x

x - x x

x - x - x - x

x - x - x - x - x - - x - x - - x

x - - - x - - - - x

x - - - x - x

x x - x x x x x x

x x - x x x x x x - x - x x - x x

x x x x x x x x

x x x x x x

x - x x - x x

x x x x x x x x

x x x x x x

x - x - x - x - x

x - x - x - x - x - - x - x - - x

x - - x - - - x

x - x x

x - - - - x - - - - x

x - - x - - - x

x - x x

x - - - x - - - x

Part430-24

430-25, 430-26Motor feeder

Motor feedershort-circuit andground-fault protection

Motor disconnecting means

Motor branch-circuitshort-circuit andground-fault protection

Motor circuit conductor

Motor controller

Motor control circuits

Motor overload protection

Part

Part

Part

Part

Part

Part

Part

Part

Part

Part

Part

Motor

Thermal protection

Secondary controllerSecondary conductors 430-23

Secondary resistor430-23 and Article 470

To Supply

/II

V

IX

IV

II

VII

VI

III

I

III

II

II

Figure 6: Diagram 430-1 of the National Electrical Code shows the essential elements of a motor branch cir-cuit. Differences in the international and North American definitions of these terms are often the source ofmisunderstandings and problems encountered with North American electrical inspectors during installation and commissioning work. A comparable diagram is also found in the Canadian code (CEC). In the latesteditions of the NEC, individual sections in Article 430 have been assigned roman numerals, Parts I throughXIV. In previous editions, capital letters were used to denote same.

National Electrical Code – Motor CircuitsNEC Article 430 – Diagramm 430-1

Main Disconnect

Short Circuit

Motor Controller

Overload

requirement and are listed for „groupinstallation”. Additionally, they havebeen evaluated as „tap conductorprotectors“ to further enhance theircapability in group installations. Thereare additional certifications beyondthat which will be described and whichallow the devices to function as stand-alone protective devices in individualmotor branch c

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