2-Component Combination Motor Controller Solutions For North America

Motor Controller for USA and Canadawww.eaton.com/moellerproducts2-Component Combination MotorController Solutions for North AmericaM3 Technical PaperDipl.-Ing. Wolfgang Esser

2-Component Combination Motor ControllerSolutions for North America– fuseless motor starters without separately mounted overload relay –Differing styles of motor startersEveryone would agree that motors are byfar the most important pieces of equipment in the machine tool and panel building industry. This paper will deal mainlywith modern aspects of switching andprotecting asynchronous or squirrel-cagemotors, still the primary workhorses of theindustry. There are essentially 2 traditionalapproaches involved in switching and protecting such motors. One uses fuses as theprimary overcurrent protective device. Theother is fuseless, and relies on motor protective switches or circuit breakers as thecore protective element. Both versions feature a separately mounted overload relay asa means to protect the motor against running overloads, and both are typically combined with motor switching and HP ratedmotor contactors to provide longer life andremote control operational capabilities forthe motor starter. Fuseless solutions havethe advantage that they are inherentlyindependent of local fusing styles and conditions, which can vary greatly from marketto market, and they also would permit, inmost cases, a relatively quick resetting ofthe circuit without exchange of components once the cause for the fault had beeneliminated. An additional safety related consideration of significant importance wouldbe that the fuseless protective devicewould operate to open all 3 poles simultaneously in the event of a fault, whereasfuses operate independently and are thusmore prone to allow single phasing conditions to develop in a circuit.The combination of a motor protectivedevice, or a circuit breaker, and a motorswitching contactor also lends itself wellto different levels of component protective co-ordination testing, such as beenpopularized for years in the IEC/EN 60947 standard, and of late as well in therecently introduced and comparableNorth American UL 60 947 industrialcontrol standard. Co-ordination levelsare indicators of the protection affordedto the circuit and a determination as towhether or not, in the event of fault,welding and inoperability of the contactorare permissible outcomes.In the IEC world, the choice betweena motor protective switch or a circuit2breaker can often be made simply onthe basis of a motor’s nominal currentrating. In North America, both types ofcomponents fall under markedly differentproduct standards (UL 508 resp. UL 489,or CSA-C22.2 No.14 resp. CSA-C22.2No. 5-09), which ultimately also impactsthe application range of both components when they are used as protectivedevices in branch circuits. Typically, theequipment would be subject to different construction requirements as well,such as the need for circuit breakers tofeature the larger electrical clearancesof distribution equipment1. In the IECworld, the situation is different, withmany manufacturers of motor protectiveswitches more apt to commonly referto their equipment as circuit breakers,making the line between both typesdecidedly more blurry. Motor protectiveswitches represent a particularly significant product grouping within Eaton, bothfrom a technical and manufacturing volume point of view. Eaton actually prefersto use the more precise term “MotorProtective Switch“ for their own devices,since they are optimally designed formotor protection and generally availablein relatively low current ranges, i.e. up toapprox. 65 A, to cover the large majorityof industrial motors. These componentsare also phase failure sensitive per therequirements of IEC/EN 60 947, which isconsidered a premium feature for motorprotection applications. Eaton, formerlyknown as Moeller is justifiably considered a pioneer in the field of motor protective circuit-breaker, to the point wherethe PKZM brand reference in the electrical industry is often used as an eponymor generic term to refer to products fromall makes in this category.The IEC product standard pertainingto a molded case circuit breaker, IEC/EN 60 947 Part 2, does not contain anyspecific testing provisions for motor pro-1 IEC style motor protective switches undergo a basiccertification in North America as manual motorcontrollers, which carries neither a main disconnectnor a short circuit protective capability. The motorcontrollers are subject to additional certification asType E self-protected combination motorcontrollers, or Type F combination motor controllers,in order to achieve the added functionality.tection. One needs to combine certaintest requirements from an additionalproduct standard, IEC/EN 60 947-4-1 forcontactors, overload relays and motorstarters, in order to legitimize the deviceas a ”Motor Protective Circuit Breaker“,or large motor protective switch. Asimilar situation exists in North America,whereby the applicable product standards for molded case circuit breakersand switches, i.e. UL 489 in the US, andCSA-C22.2 No. 5-09 in Canada, also donot include any testing provisions tospecifically verify the circuit breaker’s performance as a motor protective device.In order to establish the circuit breakeras a motor protective device, the breakermust first be listed under the UL 489product standard, and then pass additional calibration testing per the industrialcontrol standard, UL 508 [1]. In Canada,the same situation would apply, withadditional motor overload testing requiredper their equivalent standard for industrialcontrol equipment, CSA-C22.2 No.14.It can thus be said that, world-wide, amolded case circuit breaker requiresadditional calibration per the product standards for contactors and motor starters inorder to verify its performance as a motoroverload protective switch.In the IEC world, as well as in NorthAmerica, one would typically add a motorswitching contactor to a circuit breakerin order to provide motors with theadded capability of remote switching,as well as a higher switching frequencyand a longer electrical life for the motorstarter. In the IEC world, these motorstarters would predominently consist oftwo components, i.e. a circuit breakeror motor protective switch for motoroverload and short-circuit protection, anda motor contactor for direct switchingpurposes. In North America, on the otherhand, combination motor starters arestill overwhelmingly made up of at leastthree power circuit components in themotor branch circuit.North American combination motorstarters are mainly 3 componentassembliesWhereas it is common to find circuitbreakers additionally calibrated for

motor overload protection in globalregions dominated by IEC standards,circuit breakers in North America arestill commonly combined with separately mounted overload relay protectivedevices conforming to UL 508 and CSAC22.2 No.14 in motor starter circuits.Thus, the prevalent combination motorstarter configuration in the US andCanada consists of at least three powercircuit components, a number not unlikethe combination of fuses, contactor andmotor overload relay still very commonlyencountered in the IEC world for motorcircuits. In both cases, the circuit breakeror fuse fulfills the role of branch circuitprotective device (BCPD) for the branchcircuit. A typical IEC motor protectivedevice, e.g. an Eaton Moeller PKZM0, isreferred to as a motor protective switchor manual motor controller in NorthAmerica. Manual motor controllers certified per UL 508 and CSA-C22.2 No.14standards are not suitable as branchcircuit protective devices (BCPD) perthe electrical codes. In a motor branchcircuit, they would require the additionalpresence of a BCPD such as a circuitbreaker or fuse. They can fulfill the roleof a BCPD for individual motor branchcircuits if they are additionally evaluatedas Type E self-protected controllers, inwhich case they would also require theprovision of an additional terminal blockon their incoming supply side to achievethe necessary electrical clearances. Inthat capacity they can also be combinedwith conventional magnetic contactorsfor certification as Type F combinationmotor controllers [2].Two common types of combinationstarters encountered in North Americainclude a circuit breaker as the overcurrent protective device along with a motorswitching contactor and a separatelymounted overload relay. The first, andmost common, features an Instantaneous Trip circuit breaker as the protective device and accounts for the greatmajority of circuit breaker type combination motor starters in the North American industrial sector. The other form ofcircuit breaker type combination starterwould feature an inverse time circuitbreaker, most likely with a fixed overloadresponse setting (Figure 1).Circuit breakers with a fixed overloadresponse capability are very seldomencountered in the IEC world, and aremostly found in Asia or in the residentialUL 489 Inverse Time Circuit Breaker, with adjustable or,more commonly encountered, fixed overload response trips.(UL 508 Table 76.2,Construction Type C)market. The need for a circuit breakerwith fixed response settings would morelikely arise in non-motor load applicationsand would probably tend to feature largercurrents and long cable lines, for whicha closer match of the load ampacity tothe breaker’s fixed setting would beuseful in keeping down material costs,such as copper content. A circuit breakerwith an adjustable overload or long timeresponse, on the other hand, wouldalways have to be connected to a conductor whose ampacity would be equalto, or greater than, the circuit breaker’smaximum adjustable current setting,and could thus potentially lead to higheroverall installation costs. In the IEC world,instantaneous trip circuit breakers areoccasionally used for motors with unusually long starting times, and combinedwith a separately provided electronicmotor overload relay on which various tripclass settings can be selected to bettermatch the load. Instantaneous Trip circuitbreakers are certified in North America asRecognized Components only. This typeof certification is by definition restrictive,and subject to additional conditions ofacceptability in order to meet the requirements of the North American electricalcodes. In the case of these circuit break-UL 489 Motor Protective Circuit Breaker,with adjustable overload trip, with UL 508calibration, without separate overload relayI UL 489 InstantaneousTrip Circuit Breaker,without overload trips(UL 508 Table 76.2,Construction Type D)bNZM.-ME.-NAM3 new!M3 I I aM3 M3 cFigure 1: In North America, combination motor starters still predominently consist of at least 3 main power circuit components. Thenew motor protective circuit breaker Type NZM.2-ME.-NA allows for a 2 component combination motor starter solution consisting ofthe circuit breaker and a motor switching HP rated contactor.3