Compumotor

Step Motor& Servo MotorSystems and Controls

1996/1997

STEPMOTOR&SERVOMOTORSYSTEMSANDCONTROLSSTEPMOTOR&SERVOMOTORSYSTEMSANDCONTROLSSTEPMOTOR&SERVOMOTORSYSTEMSANDCONTRO

THE COMPLETE SOURCE FORPROGRAMMABLE MOTION CONTROL

COMPUMOTOR

A Broad Range of CapabilitiesIf you have a motion control prob-lem, turn to Compumotor. We offera comprehensive line-up of producttechnologies, plus we provide thetechnical support to ensure timely,expert assistance in product selec-tion, installation, programming,training and troubleshooting. Fromhands-on technical seminars tolocal Automation Technology Cen-ters to factory-trained field applica-tion engineerssolutions to yourmotion control problems are only aphone call away.A Basis to Objectively Recommendthe Best SolutionA full spectrum of motion controltechnologies allows us to objec-tively recommend the best solution

to your specific problem. We offer: Stepper motor and servo systems Half/full step and microstepping Digital and analog drives Open loop and closed loop systems Brushed and brushless motor/drives Position, velocity and torque control

servos Stand alone and peripheral controls Absolute and incremental feedback Encoder and resolver feedback

servos Direct drive rotary motors and motors

attached to gearboxes, tables, etc. Linear motors and motors mounted

to leadscrews, belt drives, etc.So, if youre looking for the finalword on motion control, turn to thecompany that has all the possibilitiesCompumotor.

1An Introduction toCompumotor

A POWERFUL LINE-UP OF PROGRAMMABLE CONTROLS

PageWorldwide Support .......... 2-3

Technical Support Team .. 4-5

Seminars ......................... 6-7

Support Software ............ 8-9

Servo vs. StepperMotor Selection ........... 10-11

Servo Systems ............ 12-13

Stepper Systems ......... 14-15

Custom Products .............. 16

Engineering Referenceand ApplicationSolutions

Compumotor providesthorough technical data andsupport for every product. InSection A, youll find motorand drive technologydefinitions, how-to applicationinformation, formulas, andapplication examples. Aspecial Motor Sizing andSelection Software diskcompliments this catalog andis available to help youdetermine the optimum motorfor your application. And if youhave any other questionsabout products or services,call your local, factory-trainedapplications engineer or ourApplications Engineeringdepartment at our toll-freefactory line: 1-800-358-9070.

Servo SystemsCompumotors servo systemsoffer power and diversity in amultitude of form factors.Compumotor offers a widerange of digital and analogservo drives for all your motionneeds, as well as convenientpackaged servo systems.Compumotors powerful servocontrollers operate stand-alone or in an AT-bus structureand are easily interfaced toPLCs, PCs or other factoryequipment.

B1-B146

Step Motor SystemsCompumotor pioneeredmicrostepping techniques toelectronically improve thesmoothness and resolution ofstep motors. The leadershipcontinues with a completerange of products, from fullstep and microsteppingsystems to packaged single-and multi-axis drive/indexersystems and powerful single-and multi-axis indexers.

C1-C160

A1-A96C

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2ManufacturingWorkcells

Our manufacturing workforceconsists of efficient workcells,all dedicated to producing aproduct family. Each workcellmember has a voice instreamlining everymanufacturing process. Theworkcell includes a memberfrom our Marketing,Applications Engineering,Customer Service, andManufacturing departmentscustomer feedback andspecial requests can bediscussed with those actuallymaking your product. Thislevel of communication givesus the flexibility to altermanufacturing steps to furnishyou with the exact productyou want. Our manufacturingworkforce is completely cross-trained to work on severaldifferent workcells. Cross-training is yet another methodwe use to efficiently respondto your order and overallproduct demand.

The Foundation forContinued Leadership

Our corporate mission is tobecome the leading supplier ofelectronic motion controlequipment worldwide.Compumotors merger in May1986, with Parker HannifinCorporation has helpedprovide the technical andfinancial resources necessaryto fulfill that role. With a 70-year history of successfullysupplying motion controlcomponents and systems,Parker Hannifin enhancesCompumotors foundation forcontinued leadership.

Our Strategy for YourSuccess

Our strategy for success issimple: provide our customerswith a competitive advantage.We do so by offeringcontinuous productinnovation, completesolutions, and unrivalledtechnical support.

Internal ManufacturingParker Hannifin has invested instate-of-the-art surface mountand automated insertionmachines to guarantee aprompt response to orders.Unlike many other companies,Parker Hannifin has theflexibility to build any productin any quantity (based ondemand) without relying on anoutside turn-key vendor tobuild our boards. If yourmanufacturing growth requiresmore Parker Hannifin product,we can grow with you! Ourmanufacturing philosophy issimple:

Authorize JIT-based vendorsto provide raw materialswith low lead times

Reduce our dock-to-stocktime required to receive theraw parts before we canbuild products

Build all boards internallywith state-of-the-art surfacemount and PCA equipment

Provide consistent leadtimes to our customersregardless of product mix

INNOVATIVE SOLUTIONS AND UNRIVALLED SUPPORT

3Quality ProductsAt Parker Hannifin, producingquality products is our numberone priority. Our products aredesigned with high qualitystandards and aremanufactured with state-of-the-art equipment andproduction methods. Beforeany product reaches ourcustomers, it must pass arigorous set of hardware andsoftware tests. JIT (Just-in-time) manufacturing and DFM(Design-for-Manufacturability)methods lend themselves tocreating the necessaryflexibility to readilyaccommodate your specialneeds. As an example of thesemanufacturing principles inaction, many of our productshave earned UL recognition.

In addition to adhering to ourown rigorous standards,Parker Hannifin is dedicated tomeeting existing qualityrequirements established bythe industry. The ISO-9000international quality standardinvolves a suppliers internalproduction processes andservices. ISO-9000 is astandard credential thatverifies that a supplier has aquality process in place. Dueto the emphasis of ISO-9000in Europe, Parker Hannifin hasalready achieved the ISO-9000 standard at its Digiplandivision. Many of the qualitypractices performed atDigiplan have been adopted atthe Compumotor division.

Two-Year WarrantyIts one thing to promisereliability, quality and service;and quite another toguarantee itespecially in aglobal marketplace. Thatswhy we offer a two-yearwarranty on our entire line ofmotors, drives, encoders, andcontrollers.

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4Local ProductAvailabilityand ServiceAround the World

At Parker Hannifin, weunderstand the demands ofthe global marketplace.Throughout North America,Europe and the Pacific Rim,our motion control productsare delivered and supportedthrough a comprehensivenetwork of AutomationTechnology Centers (ATCs).ATCs serve the industrialneeds unique to each region.

Parker HannifinsElectromechanicalTerritory Manager

Everyone promises service,but Compumotor has thepeople to assure timely, expertsupport. For example, ParkerHannifin employs a competentand motivated team ofdegreed, factory-trained fieldapplication engineers who areready to offer you assistancein product selection,installation, product/systemprogramming andtroubleshooting.

TOTAL SUPPORT FROM CONCEPT TO IMPLEMENTATION

Authorized AutomationTechnology Centers

Your local independentAutomation Technology Centerhas been factory-trained tooffer you expert service andadvice. The network includes90 organizations and morethan 125 outlets throughoutthe world. In addition to thoseservices offered by traditionaldistributors, theseorganizations specialize in theapplication of high technologyautomation equipment. ParkerHannifin works cooperativelywith its authorized ATCs torecruit, hire, and train degreedengineers for positions withATC organizations. ATCs offerlocal product availability,product demonstrations,complementary products andservices, programmingassistance, system integration,and in-depth customerseminars.

Engineering SupportTools to Make Your JobEasier

Years of experience haveculminated in a vastassortment of engineeringsupport tools that help tosimplify the sizing, selection,and installation process,design a system to customapplication requirements, andtroubleshoot existinginstallations. A few of thesetools include:

Motor Sizing and SelectionSoftware

Application ProgrammingSoftware

Application success stories

Product installation videos

In-depth handbooks onsubjects such as feed-to-length

The consolidatedengineering reference,Section A of this catalog

A customer newsletter

5ASSISTANCE AT YOUR FINGERTIPS

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1-800 ApplicationsEngineering Assistance

When you have urgentquestions, expert answers areonly a phone call away. Ateam of engineers is ready totake your call from 6:00 a.m.to 5:00 p.m. PST. Theseengineers have practical fieldexperience and are preparedto provide you with applicationand product assistancethroughout the stages of yourproject and for the life of theproduct. Just call 1-800-358-9070. Outside the U.S. call707-584-7558.

Bulletin BoardUse your modem to access awide variety of sampleprograms, CAD drawings,support software, and even amessage interface. To reachCompumotors Bulletin Board,dial 707-584-4059.

E-MailIn addition to the 1-800number, you can callCompumotor via the Internet.Designed as a question andanswer forum, leave usmessages, requests forliterature, or send and retrievefiles. Compumotors E-mailsystem is available 24 hours aday, 7 days a week. To reachour system simply punch in:tech_help@cmotor.com

FaxCompumotor offers a faxservice to customers toanswer questions and reviewshort programs. Answers willbe faxed or phoned backwithin 24 hours. To send us afax dial 707-584-3793.

6Motion ControlTechnology Training atCompumotor

Customers can attend trainingcourses at Compumotor.Training courses are availableon a variety of technical topicsas well as product-specificinstruction. The courses aredesigned to give attendeeshands-on, practical trainingwith experienced engineers. Inmany cases, the actualproduct design engineers willconduct the training. Thisprogram provides ourcustomers with a uniqueopportunity to develop abetter understanding ofapplication design,development, andprogramming. Participants willalso develop a betterunderstanding of ParkerHannifin and its commitmentto quality products andservice.

Local and In-HousePresentations Bring theLeading Edge to You

Compumotor assures youhave access to the latestinformation by conductingover 100 local seminars andproduct workshops annually. Ifyou need an in-housepresentation, talk to yourAutomation Technology Centeror field application engineer.We can customize programsto your specific requirements.

SEMINARS: PROVIDING THE TOOLS TO MAKE INFORMED DECISIONS

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7Come With a Problem,Leave With a Solution

Since 1986, our AutomationTechnology Centers haveconducted motion controlseminars for over 11,000attendees. At our seminars,youll be briefed not only onthe basics of programmablemotion control, but also on thenewest, most innovativetechnologies in the industryand given the facts to evaluatethem for your applications.

Seminars are more thaninformational programstheyre problem-solvingsessions that address yourneeds. So bring a motioncontrol problem. You canexpect to leave with a ParkerHannifin solution.

PROBLEM SOLVING WORKSHOPS & SEMINARS TO ADDRESS YOUR NEEDS

Youll Take Away MoreThan Ideas

Attendees to our seminars getmore than answers. Theyreceive presentation materials,article reprints, supportsoftware, assignments withsolutions, videos and specificapplication ideas.

Contact your localAutomation TechnologyCenter or ElectromechanicalTerritory Manager forupcoming seminars.

WorkshopsCompumotor offers full-dayworkshops that guide usersthrough the installation andapplication of its most popularproducts. Compumotorsworkshops empowerattendees with the followinginformation.

Relevant technology issues

Application design tips

Basics of motion controlhardware and software

Helpful troubleshooting tips

The workshops are designedto help you get the most outof your new Compumotorproduct in the least amount oftime. These workshops aredesigned by Compumotor andorganized, scheduled, andconducted by its authorizedATC network.

Use Motor Sizing &Selection Software forthe Right Product,Every Time

A wide range of applicationscan be solved equally well bymore than one motor.However, some applicationsare particularly appropriate foreach motor type.Compumotors Motor Sizingand Selection softwarepackage is designed to helpusers easily identify theappropriate motor size andtype for a motion application.

8WITH SUPPORT SOFTWARE, THERES NO MORE GUESS WORK

Motion ArchitectSoftware Does the Workfor You... Configure,Diagnose, Debug

Compumotors MotionArchitect is a MicrosoftWindows-based softwaredevelopment tool for 6000Series products that allowsyou to automatically generatecommented setup code, editand execute motion controlprograms, and create acustom operator test panel.The heart of Motion Architectis the shell, which provides anintegrated environment toaccess the following modules.

System ConfiguratorThismodule prompts you to fill inall pertinent set-upinformation to initiatemotion. Configurable to thespecific 6000 Seriesproduct that is selected, theinformation is then used togenerate actual 6000-language code that is thebeginning of your program.

Program EditorThismodule allows you to editcode. It also has thecommands availablethrough Help menus. Ausers guide is provided ondisk.

Terminal EmulatorThismodule allows you tointeract directly with the6000 product. Help isagain available with allcommands and theirdefinitions available forreference.

Test PanelYou cansimulate your programs,debug programs, and checkfor program flow using thismodule.

Because Its Windows,You Already Know Howto Use It

Motion Architect has beendesigned for use with all 6000Series productsfor bothservo and steppertechnologies. The versatility ofWindows and the 6000 Serieslanguage allow you to solveapplications ranging from thevery simple to the complex.

Motion Architect comesstandard with each of the6000 Series products and is atool that makes using thesecontrollers even moresimpleshortening the projectdevelopment timeconsiderably. A value-addedfeature of Motion Architect,when used with the 6000Servo Controllers, is its tuningaide. This additional module

allows you to graphicallydisplay a variety of moveparameters and see howthese parameters changebased on tuning values.

Using Motion Architect, youcan open multiple windows atonce. For example, both theProgram Editor and TerminalEmulator windows can beopened to run the program,get information, and thenmake changes to the program.

On-line help is availablethroughout Motion Architect,including interactive access tothe contents of theCompumotor 6000 SeriesSoftware Reference Guide.

9SOLVING APPLICATIONS FROM SIMPLE TO COMPLEX

Draw Your Own MotionControl Solutions withMotion ToolboxSoftware

Motion Toolbox is anextensive library of LabVIEWvirtual instruments (VIs) foricon-based programming ofCompumotors 6000 Seriesmotion controllers.

When using Motion Toolboxwith LabVIEW, programmingof the 6000 Series controller isaccomplished by linkinggraphic icons, or VIs, togetherto form a block diagram.Motion Toolboxs has a libraryof more than 150 command,status, and example VIs. Allcommand and status VIsinclude LabVIEW sourcediagrams so you can modifythem, if necessary, to suit yourparticular needs. MotionToolbox also comes with aWIndows-based installerand a comprehensive usermanual to help you gut up andrunning quickly.

CompuCAM Softwarefor Computer-AidedMotion Applications

CompuCAM is a Windows-based programming packagethat imports geometry fromCAD programs, plotter files,or NC programs andgenerates 6000 codecompatible withCompumotors 6000 Seriesmotion controllers. Availablefor purchase fromCompumotor, CompuCAM isan add-on module which isinvoked as a utility from themenu bar of Motion Architect.From CompuCAM, run yourCAD software package. Oncea drawing is created, save itas either a DXF file, HP-GLplot file or G-code NCprogram. This geometry isthen imported intoCompuCAM where the 6000code is generated. Aftergenerating the program, youmay use Motion Architectfunctions such as editing ordownloading the code forexecution.

Servo Control is Yourswith Servo TunerSoftware

Compumotor combines the6000 Series servo controllerswith Servo Tuner software.The Servo Tuner is an add-onmodule that expands andenhances the capabilities ofMotion Architect.

Motion Architect and theServo Tuner combine toprovide graphical feedback ofreal-time motion informationand provide an easyenvironment for setting tuninggains and related systemparameters as well asproviding file operations tosave and recall tuningsessions.

Windows is a registered trademark of Microsoft Corporation. Motion Architect is aregistered trademark of Parker Hannifin Corporation, Compumotor Division. MotionToolbox is a trademark of Snider Consultants, Inc. CompuCAM is a trademark ofParker Hannifin Corporation, Compumotor Division.

Motion BuilderSoftware for EasyProgramming of the6000 Series

Motion Builder revolutionizesmotion control programming.This innovative software allowsprogrammers to program in away they are familiar withaflowchart-style method.Motion Builder decreases thelearning curve and makesmotion control programmingeasy.

Motion Builder is a MicrosoftWindows-based graphical-development environmentwhich allows expert andnovice programmers to easilyprogram the 6000 Seriesproducts without learning anew programming language.Simply drag and drop visualicons that represent themotion functions you want toperform.

Motion Builder is a completeapplication developmentenvironment. In addition tovisually programming the 6000Series products, users mayconfigure, debug, download,and execute the motionprogram.

10 SERVO VS. STEPPER

Motor Types and TheirApplications

The following section will giveyou some idea of theapplications that areparticularly appropriate foreach motor type, together withcertain applications that arebest avoided. It should bestressed that there is a widerange of applications whichcan be equally well met bymore than one motor type,and the choice will tend to bedictated by customerpreference, previousexperience or compatibilitywith existing equipment.

A helpful tool for selecting theproper motor for yourapplication is CompumotorsMotor Sizing and Selectionsoftware package. Using thissoftware, users can easilyidentify the appropriate motorsize and type.

SERVO VERSUS STEPPER... WHAT YOU NEED TO KNOW

High torque, low speedcontinuous duty applicationsare appropriate to the stepmotor. At low speeds it is veryefficient in terms of torqueoutput relative to both sizeand input power.Microstepping can be used toimprove smoothness in low-speed applications such as ametering pump drive for veryaccurate flow control.

High torque, highspeed

continuous duty applicationssuit the servo motor, and infact a step motor should beavoided in such applicationsbecause the high-speedlosses can cause excessivemotor heating.

Short, rapid, repetitivemoves

are the natural domain of thestepper due to its high torqueat low speeds, good torque-to-inertia ratio and lack ofcommutation problems. Thebrushes of the DC motor canlimit its potential for frequentstarts, stops and directionchanges.

Speed

revs/min 0 180 360 720 1080 1440 1800 3000 6000

revs/sec 0 3 6 12 18 24 30 50 100

Series Page Torque (oz-in)

PDS & PDX Series C55 910 850 650 426 270 170 130 70

PK130 C67 4500 5000 3300 3000 2200 1450 1000 750

ZETA4 C17 400 400 380 350 200 150 125 100

ZETA6104 C17 400 400 380 350 200 150 125 100

S & SX C37 1900 1900 1800 1500 1000 750 600 350

LN C51 85 60 35 10

APEX Series B17 8400 8300 8200 8100 8000 7900 4700 3300 1500

TQ10 B39 25 324 323 322 318 319 318 313 114

BLH & BLHX B47 1850 1850 1850 1850 1850 1850 1850 430 70

Z Series B61 18000 17825 17650 17270 16800 11300 11100 7320 1300

The Right Motor/Drive Technology for Your Application

Low speed, highsmoothnessapplications

are appropriate formicrostepping or direct driveservos.

Applications inhazardousenvironments

or in a vacuum may not beable to use a brushed motor.Either a stepper or a brushlessmotor is called for, dependingon the demands of the load.Bear in mind that heatdissipation may be a problemin a vacuum when the loadsare excessive.

Series Page Speed (revs/sec) 0 1.0 2.0 3.0 4.0

Dynaserv B80 Torque (ft-lb) 370 330 50 50 40Direct Drive

Brushless Servos*

Step MotorsFull/Half/Mini

Microstepping

Brushless Servos*

* The torque values indicated are peak values. Please refer to the product section for full technical data.

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SELECTING THE MOTOR THAT SUITS YOUR APPLICATION

SERVO VS. STEPPER

SE

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Will a stepper meetthe torque/speed

requirements?

Do you need to runcontinuously atspeeds above

2000 rpm?

Do you need tocontrol torque?

Does the loadchange rapidly

during operation?

Do you need todetect position

loss OR measureactual load

position to correctfor backlash?

Use a stepperUse a microstepping,

hybrid servo, ordirect drive servo

Is quiet operationimportant?

Is low-speedsmoothnessimportant?

Is quiet operationimportant?

Use a microsteppingwith encoderfeedback?

Is rapid settlingimportant?

Use a brush servo.

Are there anyother brush

servos in thesystem?

Must the motorEITHER1)

2)

Will a brushservo meet

the torque/speedrequirements?

Use a brushlessservo.

Is there a hybridservo which meetsthe torque/speed

requirements?

Try a hybridservo with

encoder feedbackif necessary.

Really quiet?

If there are otherbrushless motors, it maybe better to be consistent

with this one.Otherwise use a brush servo.

Highertorque/speedtechnology.

Start Here

No

No

NoYes

Yes

Yes

No

Yes

YesYes

Yes

No No

No

No

Yes

No

No

No

Yes

No

Yes

No

Yes

No No

Yes

Will a brushlessservo meet

the torque/speedrequirements?

Be maintenance-freeOperate in anyenvironment

The flow chart seen below will guide you to therecommended drive technology.

Start at the top left corner and proceed by answering the givenquestions until you end at the recommended drive technology.You can then proceed to the stepper or servo sections of thecatalog to determine what type of controller is required for yourapplication.

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COMPUMOTOR: YOUR SERVO CONTROL SPECIALIST

Powerful ControllersDesigned with the Userin Mind

Compumotors servocontrollers offer power anddiversity with the capability ofsupporting multi-axisapplications, in 1-, 2-, or 4-axis configurations. Operatingstand-alone or with a hostcomputer, these controllersincorporate the leadingprocessor technology in theindustry. Support for I/O,operator interface, andcommunications is standard inall of the controllers. Othercomplex operations includingmulti-axis following can beachieved with very little effort.

Systems Made Simpleby Design

At Compumotor, we havedesigned each system withthe user in mind. Our goal is toprovide you with everythingthat is required to get yourCompumotor servo system upand running quickly. Thisimplies that every unit shippedfrom our factory includes thenecessary cables,documentation, and software.Because the needs of everyuser is different, drives andcontrollers are eitherpackaged with a power supplyor provided separately to suitthe needs of the specificsystem. System wiring canoften be nightmarish withother controllers and drives.However, Compumotorprovides screw-terminalconnections to make wiringstraight forward and trouble-free. At Compumotor, we takeeasy-to-use seriously,because we know you areserious about saving valuableproject development time.

Tuning Your ServoServo tuningone of the morechallenging aspects of servomotion controlis supportedwith powerful software toolsoffered by Compumotor.Tuning modules graphicallydepict actual versusprogrammed motion andperformance, greatly reducingthe time required to tune theservo system.

Extensive servo applicationexperience allows us toprovide useful and easy-to-usefront-end software to ourcustomers. These programsreduce labor-intensive set-upand programming tasks.Examples of these programsinclude:

Motion Architect, which isused to set up, test, andcommunicate with the 6000Series of controllers,

Servo Tuner, whichcombines with MotionArchitect to providegraphical feedback of moveinformation and makesservo tuning a snap,

Xware, a terminal emulationsoftware package, usedwith our combinationcontroller drive packages.

The Power of the6000 Series

Compumotor combines the6000 Series products withMotion Architectand servocontrol never looked so good.The 6000 family provides 1 to4 axes of servo control, instand-alone or AT-bus-basedsystems as well as single axispackaged drive/controllerunits. All of the productsaccept incremental encoderfeedback, and add valuableservo tuning capability to thepackage through MotionArchitects optional ServoTuner Module. Position-basedfollowing is standard on all6000 Series products.

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FLEXIBLE AND EASY TO USE CONTROLLER AND DRIVE COMBINATIONS

Pre-engineered ACBrushless ServoSystems

Theres no need to mix andmatch components withCompumotors digital ACbrushless servo systemstheyre completely pre-engineered for optimumperformance. That meanseasy set-up and lowmaintenance. Compumotorbrushless servo systems offerhigh torque per motor size andweight, rapid acceleration andsmoother machineoperationall in one proven,pre-engineered package.

Pretested speed, torque andacceleration performanceassures that every systemmeets your designrequirements. Each single axismodel includes everythingneededmotor, drive,resolver, cables and feedback.6000 Series and X versioncontroller systems include acontroller integral to the drivepackage.

Controller and DriveCombinationsExcellent Options forSingle-AxisApplications

An industry leader ininnovation, Compumotorintroduced the X Seriesthefirst system that combinedcontroller and drive electronicsin one package. The result?The most versatile, cost-effective, single-axis motioncontrol systems available. Butwe have not stopped there.Compumotor has nowcombined the 6000 servocontroller with the APEX driveto provide the easiest to usepackaged servo system on themarket.

State of the ArtPrecision with theDynaserv

If high accuracy andrepeatability are required,Dynaserv is the answer. Byutilizing advanced resolver andencoder techniques, theDynaserv has accuracies to30 arc-sec and repeatabilitiesup to 2 arc-sec. Theresolution is also astoundingwith values up to 1,024,000steps/rev.

When it comes to loads,Dynaserv has a sophisticatedservo algorithm allowingcontrollability of extremelylarge loads. The proprietarycross-roller bearing design cancarry over 4 tons incompression and 296 ft-lbs ofoverhung load.

The APEX Series:Drives or CompletePackaged Systems

Compumotors competitivelypriced APEX family of servoproducts includes both servodrives and complete packagedservo systems. APEX driveswere designed for use withservo controllers, in torque orvelocity mode. Flexibility is theword to describe these drives,since they mix and match withall of Compumotors controls.These analog input drives areavailable for single or multi-axis applications, offer manymotor options, and come in avariety of power ranges.

APEX packaged controller/drive systems offertremendous value by savingboth space and money. Thesesystems marry Compumotors6000 Series of controllers withthe APEX family of drivesresulting in a single-axiscontroller and servo drive inone package that usesCompumotors front end 6000software tools for quick andeasy operation.

High Speed Capabilitywith the BL Series

The BL Series is a cost-effective solution in a widevariety of brushless servoapplications. With high-speedcapability in excess of 10,000rpm, the system offersindustry-standard analog input,position feedback from thebuilt-in incremental encoder,torque and velocity monitoroutputs, and rack compatibledesign. The BL Drive operatesin torque or velocity amplifiermode, and can be suppliedwith an integral positioner toaccept motion controlcommands via an RS-232Clink.

Turn to the B Sectionfor more informationand complete productspecifications onCompumotors wideselection of servomotor systems.

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FROM POWERFUL AND COMPACT FULL OR MINISTEPPING SYSTEMS...

Ministepping MotorDrives

The PDX Series drivescombine built-in RS-232Cindexers with advancedministepping techniques foroutput resolutions of up to4000 steps/revolution. ThePDX Series drives provide aunique level of functionality ina compact package, and offeran excellent cost/performanceratio. The ministeppingcapability offers improvedsmoothness over conventionalfull and half step drives. Thedrives ability to run directlyfrom local supply voltagesvirtually anywhere in the worldsimplifies the design ofequipment built for export,making the units ideal forOEMs and system integrators.

Low-cost, Slow-speedRotation

The PDS Series offerscompletely self-contained low-cost motion control forapplications that require acombination of good dynamicperformance and smoothslow-speed rotation. DigiplansPDS Series features built-inintelligent switch-mode powersupply that allows direct on-line operation from any ACsupply in the range of 95V to265V without the need foradjustment. PDS drives areavailable with 3A and 5Aoutputs, and a 70V DC busmaximizes high-speed torque.

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High Resolution andSmooth Control Makethe Job Easier

Microstepping, a techniquepioneered by Compumotor,offers precise positioningexceptional smoothness atvery slow speeds.

Compumotors precisionmicrostepping electronics offermore than smooth, low-speedoperation. They also providesmooth acceleration anddeceleration which eliminatesdamaging vibration, shock,overshoot, and ringing.

25,000 Steps/RevStandard

Compumotors 25,000 stepsper revolution has become theindustrial standard formicrostepping. A wide rangeof resolutions are availablefrom 2,000 to 100,000 stepsper revolution for closed loopapplications requiring sub-micron resolutions.

While microsteppingsincreased positional resolutionisnt necessary for allapplications, its low velocityripple and resonance controlassures smooth machineoperation thats unattainablewith conventional full stepmotors and many servosystems.

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...TO SMOOTH AND PRECISE MICROSTEPPING SYSTEMS

Turn to the C Sectionfor more informationand complete productspecifications onCompumotors wideselection of steppermotor systems.

Indexer and DriveCombinations: ExcellentOptions for Single AxisApplications

Compumotors ZETA6104 andSX Series combine thefunctions of an indexer andmicrostepping drive in onecompact system. Each modelis capable of storing multiplemove motion programs inbattery backed memory.Programs can be selected in avariety of ways including BCDswitches, programmablecontrollers or a computer via aRS-232C interface.

The ZETA6104 combines theflexibility of the 6000 Seriescontrols with the revolutionarydesign features of the ZETAdrive. As a member of the6000 Series, the ZETA6104offers all the capabilities of the6000 language and the benefitof Motion Architectdevelopment software andother 6000 Series-compatiblesoftware packages.

The SX uses a high-levelprogramming language whichevolved from CompumotorsX-language. This popularlanguage provides both ease-of use and the ability toprogram complex motion.

UL-RecognizedMicrostepping Systems

Todays laboratory and factoryautomation products faceincreasingly stringentperformance and safetycriteria. To meet thesestandards, our ZETA Seriesand S Series microsteppingsystems are certified as ULRecognized Componentsunder the UL508 safetystandard covering IndustrialControl Equipment.

Powerful IndexersDesigned with the Userin Mind

Compumotors indexers offerthe power and diversity ofsupporting multi-axisapplications, in 1-, 2-, or 4-axis configurations. Theseindexers incorporate theleading processor technologyin the industry and operatestand-alone or with a hostcomputer. Support for I/O,operator interface, andcommunications is standard inall of the indexers. Othercomplex operations includingmulti-axis following can beachieved almost effortlessly.

ZETA: Revolution inMicrosteppingTechnology

Compumotors innovativeleadership continues with theintroduction of the ZETASeriesa true revolution inmicrostepping technology.

The ZETA drive incorporatespatentable techniques knownas active damping andelectronic viscosity. The resultis higher throughput in asmaller package systemandall at a reduced cost.

The ZETA Series combines thebenefits of a smaller footprint,with increased throughput byreducing settling time anddecreasing motor vibration.The user has selectabledamping to optimizeperformance, and reduceaudible noise. Thiscombination of innovativefeatures makes the ZETA drivethe most cost-effective andhighest performingmicrostepping systemsavailable today.

Open or Closed LoopCompumotor offers open- orclosed-loop pre-engineeredmicrostepping systems with acomplete range of motors.Both incremental and absoluteencoder feedback is available.

The Power of the 6000Series

Compumotor combines the6000 Series with MotionArchitect, and microsteppingcontrol is better than everbefore. The 6000 familyprovides 1 to 4 axes of controlin stand-alone or AT-bus-based systems as well as oneand two axis packaged drive/indexer units. All of theproducts accept incrementalencoder feedback in order todetect stalls, verify position,and correct for positioningerrors.

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CUSTOM PRODUCTS... JUST GIVE US A CALL

AdaptabilityCompumotor will enhancestandard catalog products byadding software and hardwarefeatures for your uniqueapplication requirements.

ConnectabilityOut of the box componentinstallation can be even easierwith custom cables, modifiedmotors and customer specificinterfaces.

Complete SubsystemsCompumotor can providecustom packaging, privatelabeling or severalcomponents integrated into asingle part number to saveengineering and productiontime. From your initial conceptthrough custom productcompletion, Compumotor isyour source for applicationspecific flexibility.

If you dont find what yourelooking for in this catalog,contact your AutomationTechnology Center or yourCompumotor Electro-mechanical Territory Managerfor application-specific motioncontrol solutions involvingcustomized:

Motors

Controls

Drives

Absolute encoders

Software

Hardware

Cabling

CU S T

OM

IZ

E!

EngineeringReference andApplicationSolutions

A1

PLCProgrammableLogic Controller

Controller Drive

BallscrewRotating Nut

Motor

Table

DrillHead

Drive/Controller

Motor

Joystick

Drive

Drive

Motor

Indexer

TransferMachine

Circuit Board

Rotary Indexer

A2

Motor TechnologiesIntroductionMotion control, in its widest sense, could relate toanything from a welding robot to the hydraulicsystem in a mobile crane. In the field of ElectronicMotion Control, we are primarily concerned withsystems falling within a limited power range,typically up to about 10HP (7KW), and requiringprecision in one or more aspects. This may involveaccurate control of distance or speed, very oftenboth, and sometimes other parameters such astorque or acceleration rate. In the case of the twoexamples given, the welding robot requires precisecontrol of both speed and distance; the cranehydraulic system uses the driver as the feedbacksystem so its accuracy varies with the skill of theoperator. This wouldnt be considered a motioncontrol system in the strict sense of the term.

Our standard motion control system consists ofthree basic elements:

Fig. 1 Elements of motion control system

The control system. The actual task performed bythe motor is determined by the indexer/controller; itsets things like speed, distance, direction andacceleration rate. The control function may bedistributed between a host controller, such as adesktop computer, and a slave unit that acceptshigh-level commands. One controller may operatein conjunction with several drives and motors in amulti-axis system.

Well be looking at each of these system elementsas well as their relationships to each other.

The motor. This may be a stepper motor (eitherrotary or linear), a DC brush motor or a brushlessservo motor. The motor needs to be fitted withsome kind of feedback device unless it is a steppermotor.

Fig. 2 shows a system complete with feedback tocontrol motor speed. Such a system is known as aclosed-loop velocity servo system.

Fig. 2 Typical closed loop (velocity) servo system

Table of ContentsMotor Applications A3Step Motor Technology A4Linear Step Motor Technology A9Common Questions Regarding Step Motors A12DC Brush Motor Technology A13Brushless Motor Technology A17Hybrid Servo Technology A20Direct Drive Motor Technology A21Step Motor Drive Technology A23Microstepping Drive Technology A29Analog and Digital Servo Drives A31Brushless Servo Drive Technology A34Servo Tuning A36Feedback Devices A39Machine Control A45Control System Overview A46Understanding I/O Modules A48Serial & Parallel Communications A51Electrical Noise Symptoms & Solutions A52Emergency Stop A54System Selection Considerations A55Motor Sizing and Selection Software A57System Calculations Move Profiles A58System Calculations Leadscrew Drives A60System Calculations Direct Drives A63System Calculations Gear Drives A64System Calculations Tangential Drives A65System Calculations Linear Motors A66Glossary of Terms A68Technical Data A71Application Examples A72

The drive. This is an electronic power amplifier thatdelivers the power to operate the motor in responseto low-level control signals. In general, the drive willbe specifically designed to operate with a particularmotor type you cant use a stepper drive tooperate a DC brush motor, for instance.

CommandSignals

High-LevelCommands

HostComputer

or PLC

Indexer/Controller

Drive Motor

Hybrid StepperDC ServoBrushless

Servo LinearStepper

Tachometer

Drive MotorController

Velocity Feedback

Overview

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Motor TechnologiesApplication Areas of Motor TypesThe following section gives some idea of theapplications that are particularly appropriate foreach motor type, together with certainapplications that are best avoided. It should bestressed that there is a wide range ofapplications that can be equally well met bymore than one motor type, and the choice willtend to be dictated by customer preference,previous experience or compatibility withexisting equipment.

Cost-conscious applications will always beworth attempting with a stepper, as it willgenerally be hard to beat the steppers price.This is particularly true when the dynamicrequirements are not severe, such as settingtype applications like positioning a guillotineback-stop or a print roller.

High-torque, low-speed, continuous-dutyapplications are also appropriate for stepmotors. At low speeds, it is very efficient interms of torque output relative to both size andinput power. Microstepping can improve low-speed applications such as a metering pumpdrive for very accurate flow control.

High-torque, high-speed, continuous-dutyapplications suit the servo motor, and in fact, astep motor should be avoided in suchapplications because the high-speed losses cancause excessive motor heating. A DC motorcan deliver greater continuous shaft power athigh speeds than a stepper of the same framesize.

Short, rapid, repetitive moves are the naturaldomain of steppers or hybrid servos due to theirhigh torque at low speeds, good torque-to-inertia ratio and lack of commutation problems.The brushes of the DC motor can limit itspotential for frequent starts, stops and directionchanges.

Low-friction, mainly inertial loads can beefficiently handled by the DC servo provided thestart/stop duty requirements are not excessive.This type of load requires a high ratio of peak tocontinuous torque and in this respect the servomotor excels.

Very arduous applications with a highdynamic duty cycle or requiring very highspeeds may require a brushless motor. Thissolution may also be dictated whenmaintenance-free operation is necessary.

Low-speed, high-smoothness applicationsare appropriate for microstepping or direct driveservos.

Applications in hazardous environments or ina vacuum may not be able to use a brushmotor. Either a stepper or a brushless motor iscalled for, depending on the demands of theload. Bear in mind that heat dissipation may bea problem in a vacuum when the loads areexcessive.

Will a stepper meetthe torque/speed

requirements?

Do you need to runcontinuously atspeeds above

2000 rpm?

Do you need tocontrol torque?

Does the loadchange rapidly

during operation?

Do you need todetect position

loss OR measureactual load

position to correctfor backlash?

Use a stepperUse a microstepping,

hybrid servo, ordirect drive servo

Is quiet operationimportant?

Is low-speedsmoothnessimportant?

Is quiet operationimportant?

Use a microsteppingwith encoderfeedback?

Is rapid settlingimportant?

Use a brush servo.

Are there anyother brush

servos in thesystem?

Must the motorEITHER1)

2)

Will a brushservo meet

the torque/speedrequirements?

Use a brushlessservo.

Is there a hybridservo which meetsthe torque/speed

requirements?

Try a hybridservo with

encoder feedbackif necessary.

Really quiet?

If there are otherbrushless motors, it maybe better to be consistent

with this one.Otherwise use a brush servo.

Highertorque/speedtechnology.

Start Here

No

No

NoYes

Yes

Yes

No

Yes

YesYes

Yes

No No

No

No

Yes

No

No

No

Yes

No

Yes

No

Yes

No No

Yes

Will a brushlessservo meet

the torque/speedrequirements?

Be maintenance-freeOperate in anyenvironment

A4

Motor TechnologiesStepper MotorsStepper Motor BenefitsStepper motors have the following benefits:

Low cost Ruggedness Simplicity in construction High reliability No maintenance Wide acceptance No tweaking to stabilize No feedback components are needed They work in just about any environment Inherently more failsafe than servo motors.

There is virtually no conceivable failure within thestepper drive module that could cause the motor torun away. Stepper motors are simple to drive andcontrol in an open-loop configuration. They onlyrequire four leads. They provide excellent torque atlow speeds, up to 5 times the continuous torque ofa brush motor of the same frame size or double thetorque of the equivalent brushless motor. This ofteneliminates the need for a gearbox. A stepper-drivensystem is inherently stiff, with known limits to thedynamic position error.

A4

Stepper Motor DisadvantagesStepper motors have the following disadvantages:

Resonance effects and relatively long settlingtimes

Rough performance at low speed unless amicrostep drive is used

Liability to undetected position loss as a result ofoperating open-loop

They consume current regardless of loadconditions and therefore tend to run hot

Losses at speed are relatively high and can causeexcessive heating, and they are frequently noisy(especially at high speeds).

They can exhibit lag-lead oscillation, which isdifficult to damp. There is a limit to their availablesize, and positioning accuracy relies on themechanics (e.g., ballscrew accuracy). Many ofthese drawbacks can be overcome by the use ofa closed-loop control scheme.

Note: The Compumotor Zeta Series minimizes orreduces many of these different stepper motordisadvantages.

There are three main stepper motor types: Permanent Magnet (P.M.) Motors Variable Reluctance (V.R.) Motors Hybrid Motors

Courtesy Airpax Corp., USA

N

N N N

NS

S SS

S

S

SS

SN

N NN

NSN

S

Fig. 1.1 Canstack or permanent magnet motor

Coil A

Coil B

Rotor

Stator cup A

Stator cup B

Output shaft

Variable Reluctance (V.R.) Motors. There is nopermanent magnet in a V.R. motor, so the rotorspins freely without detent torque. Torque outputfor a given frame size is restricted, although thetorque-to-inertia ratio is good, and this type of motoris frequently used in small sizes for applications suchas micro-positioning tables. V.R. motors are seldomused in industrial applications (having no permanentmagnet). They are not sensitive to current polarityand require a different driving arrangement than theother motor types.

Fig. 1.2 Variable reluctance motor

Permanent Magnet (P.M.) Motors. The tin-can orcanstack motor shown in Fig. 1.1 is perhaps themost widely-used type in non-industrialapplications. It is essentially a low-cost, low-torque,low-speed device ideally suited to applications infields such as computer peripherals. The motorconstruction results in relatively large step angles,but their overall simplicity lends itself to economichigh-volume production at very low cost. The axial-air gap or disc motor is a variant of the permanentmagnet design which achieves higher performance,largely because of its very low rotor inertia.However this does restrict the applications of themotor to those involving little inertia. (e.g.,positioning the print wheel in a daisy-wheel printer).

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Motor TechnologiesHybrid Motors. The hybrid motor shown in Fig. 1.3is by far the most widely-used stepper motor inindustrial applications. The name is derived from thefact that it combines the operating principles of theother two motor types (P.M. & V.R.). Most hybridmotors are 2-phase, although 5-phase versions areavailable. A recent development is the enhancedhybrid motor, which uses flux-focusing magnets togive a significant improvement in performance,albeit at extra cost.

Fig. 1.3 Hybrid stepper motor

Housing

Non-magneticStainlessSteel Shaft

Rotor

PrelubricatedBearing

Stator

Fig. 1.4 Simple 12 step/rev hybrid motor

The rotor of this machine consists of two polepieces with three teeth on each. In between thepole pieces is a permanent magnet that ismagnetized along the axis of the rotor, making oneend a north pole and the other a south pole. Theteeth are offset at the north and south ends asshown in the diagram.

The stator consists of a shell having four teeth thatrun the full length of the rotor. Coils are wound onthe stator teeth and are connected together inpairs.

With no current flowing in any of the motorwindings, the rotor will take one of the positionsshown in the diagrams. This is because thepermanent magnet in the rotor is trying to minimizethe reluctance (or magnetic resistance) of the fluxpath from one end to the other. This will occurwhen a pair of north and south pole rotor teeth arealigned with two of the stator poles. The torquetending to hold the rotor in one of these positions isusually small and is called the detent torque. Themotor shown will have 12 possible detent positions.

If current is now passed through one pair of statorwindings, as shown in Fig. 1.5(a), the resulting northand south stator poles will attract teeth of theopposite polarity on each end of the rotor. Thereare now only three stable positions for the rotor, thesame as the number of rotor teeth. The torquerequired to deflect the rotor from its stable positionis now much greater, and is referred to as theholding torque.

Fig. 1.5 Full stepping, one phase on

The operation of the hybrid motor is most easilyunderstood by looking at a very simple model thatwill produce 12 steps per rev. (Fig. 1.4).

N

S

N

N

S

SN

S

1A

2B2A

1B

N

S

N

N

S

S

N S

N

NN

S

SS

S N

S

S

S

N

N

N

S

N

S

SNN

NS

N

S

(a) (b)

(c) (d)

By changing the current flow from the first to thesecond set of stator windings (b), the stator fieldrotates through 90 and attracts a new pair of rotorpoles. This results in the rotor turning through 30,corresponding to one full step. Reverting to the firstset of stator windings but energizing them in theopposite direction, we rotate the stator fieldthrough another 90 and the rotor takes another30 step (c). Finally, the second set of windings areenergized in the opposite direction (d) to give athird step position. We can now go back to thefirst condition (a), and after these four steps therotor will have moved through one tooth pitch. Thissimple motor therefore performs 12 steps per rev.Obviously, if the coils are energized in the reversesequence, the motor will go round the other way.

A6

Motor TechnologiesIf two coils are energized simultaneously (Fig. 1.6),the rotor takes up an intermediate position since itis equally attracted to two stator poles. Greatertorque is produced under these conditions becauseall the stator poles are influencing the rotor. Themotor can be made to take a full step simply byreversing the current in one set of windings; thiscauses a 90 rotation of the stator field as before. Infact, this would be the normal way of driving themotor in the full-step mode, always keeping twowindings energized and reversing the current ineach winding alternately.

Fig. 1.6 Full stepping, two phase on

N

N S

S

N

N

N

SS

S

S

N S

N

N

NN

S

SS

N

S N

S

S

SS

N

NN

S

S N

N

S

S NN

N

S

By alternately energizing one winding and then two(Fig. 1.7), the rotor moves through only 15 at eachstage and the number of steps per rev will bedoubled. This is called half stepping, and mostindustrial applications make use of this steppingmode. Although there is sometimes a slight loss oftorque, this mode results in much bettersmoothness at low speeds and less overshoot andringing at the end of each step.

Fig. 1.7 Half stepping

S N

S

S NN

N

S

S

S N

N

S

S NN

N

S

S

N

S

SNN

NS

motor and drive characteristics). In the half-stepmode, we are alternately energizing two phasesand then only one as shown in Fig. 1.9. Assumingthe drive delivers the same winding current in eachcase, this will cause greater torque to be producedwhen there are two windings energized. In otherwords, alternate steps will be strong and weak.This does not represent a major deterrent to motorperformancethe available torque is obviouslylimited by the weaker step, but there will be asignificant improvement in low-speed smoothnessover the full-step mode.

Clearly, we would like to produce approximatelyequal torque on every step, and this torque shouldbe at the level of the stronger step. We can achievethis by using a higher current level when there isonly one winding energized. This does not over-dissipate the motor because the manufacturerscurrent rating assumes two phases to be energized(the current rating is based on the allowable casetemperature). With only one phase energized, thesame total power will be dissipated if the current isincreased by 40%. Using this higher current in theone-phase-on state produces approximately equaltorque on alternate steps (see Fig. 1.10).

Fig. 1.8 Full step current, 2-phase on

Current Patterns in the Motor WindingsWhen the motor is driven in its full-step mode,energizing two windings or phases at a time (seeFig. 1.8), the torque available on each step will bethe same (subject to very small variations in the

1 2 3 4

Phase 1

Phase 2

Fig. 1.9 Half step current

1 2 3 4 5 6 7 8

Phase 1

Phase 2

Fig. 1.10 Half step current, profiled

1 2 3 4 5 6 7 8

Phase 1

Phase 2

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Motor TechnologiesWe have seen that energizing both phases withequal currents produces an intermediate stepposition half-way between the one-phase-onpositions. If the two phase currents are unequal, therotor position will be shifted towards the strongerpole. This effect is utilized in the microsteppingdrive, which subdivides the basic motor step byproportioning the current in the two windings. In thisway, the step size is reduced and the low-speedsmoothness is dramatically improved. High-resolution microstep drives divide the full motor stepinto as many as 500 microsteps, giving 100,000steps per revolution. In this situation, the currentpattern in the windings closely resembles two sinewaves with a 90 phase shift between them (seeFig. 1.11). The motor is now being driven very muchas though it is a conventional AC synchronousmotor. In fact, the stepper motor can be driven inthis way from a 60 Hz-US (50Hz-Europe) sine wavesource by including a capacitor in series with onephase. It will rotate at 72 rpm.

Fig. 1.11 Phase currents in microstep mode

Standard 200-Step Hybrid MotorThe standard stepper motor operates in the sameway as our simple model, but has a greater numberof teeth on the rotor and stator, giving a smallerbasic step size. The rotor is in two sections asbefore, but has 50 teeth on each section. The half-tooth displacement between the two sections isretained. The stator has 8 poles each with 5 teeth,making a total of 40 teeth (see Fig. 1.12).

Phase 1 Current: Zero

Phase 2 Current: Zero

+-

+-

Fig. 1.12 200-step hybrid motor

RotorStator

If we imagine that a tooth is placed in each of thegaps between the stator poles, there would be atotal of 48 teeth, two less than the number of rotorteeth. So if rotor and stator teeth are aligned at 12oclock, they will also be aligned at 6 oclock. At 3oclock and 9 oclock the teeth will be misaligned.However, due to the displacement between thesets of rotor teeth, alignment will occur at 3 oclockand 9 oclock at the other end of the rotor.

The windings are arranged in sets of four, andwound such that diametrically-opposite poles arethe same. So referring to Fig. 1.12, the north polesat 12 and 6 oclock attract the south-pole teeth atthe front of the rotor; the south poles at 3 and 9oclock attract the north-pole teeth at the back. Byswitching current to the second set of coils, thestator field pattern rotates through 45. However, toalign with this new field, the rotor only has to turnthrough 1.8. This is equivalent to one quarter of atooth pitch on the rotor, giving 200 full steps perrevolution.

Note that there are as many detent positions asthere are full steps per rev, normally 200. Thedetent positions correspond with rotor teeth beingfully aligned with stator teeth. When power isapplied to a stepper drive, it is usual for it toenergize in the zero phase state in which there iscurrent in both sets of windings. The resulting rotorposition does not correspond with a natural detentposition, so an unloaded motor will always move byat least one half step at power-on. Of course, if thesystem was turned off other than in the zero phasestate, or the motor is moved in the meantime, agreater movement may be seen at power-up.

Another point to remember is that for a givencurrent pattern in the windings, there are as manystable positions as there are rotor teeth (50 for a200-step motor). If a motor is de-synchronized, theresulting positional error will always be a wholenumber of rotor teeth or a multiple of 7.2. A motorcannot miss individual steps position errors ofone or two steps must be due to noise, spuriousstep pulses or a controller fault.

A8

Motor Technologies

Fig. 1.14 also shows that the rotor flux only has tocross a small air gap (typically 0.1mm or 0.004")when the rotor is in position. By magnetizing therotor after assembly, a high flux density is obtainedthat can be largely destroyed if the rotor isremoved. Stepper motors should therefore not bedismantled purely to satisfy curiosity, since theuseful life of the motor will be terminated.

Because the shaft of the motor passes through thecenter of the permanent magnet, a non-magneticmaterial must be used to avoid a magnetic short-circuit. Stepper shafts are therefore made ofstainless steel, and should be handled with care.Small-diameter motors are particularly vulnerable ifthey are dropped on the shaft end, as this willinvariably bend the shaft.

To produce a motor with a higher torque output,we need to increase the strength of both thepermanent magnet in the rotor and the fieldproduced by the stator. A stronger rotor magnetcan be obtained by increasing the diameter, givingus a larger cross-sectional area. However,increasing the diameter will degrade theacceleration performance of the motor becausethe torque-to-inertia ratio worsens (to a firstapproximation, torque increases with diametersquared but inertia goes up by the fourth power).Nevertheless, we can increase torque outputwithout degrading acceleration performance by

Occasionally a 5-lead motor may be encountered.These are not recommended since they cannot beused with conventional bipolar drives requiringelectrical isolation between the phases.

Looking at the motor longitudinal section (Fig. 1.14),we can see the permanent magnet in the rotor andthe path of the flux through the pole pieces and thestator. The alternating flux produced by the statorwindings flows in a plane at right angles to thepage. Therefore, the two flux paths are at right

Bifilar WindingsMost motors are described as being bifilar wound,which means there are two identical sets ofwindings on each pole. Two lengths of wire arewound together as though they were a single coil.This produces two windings that are electrically andmagnetically almost identical if one coil were to bewound on top of the other, even with the samenumber of turns, the magnetic characteristicswould be different. In simple terms, whereas almostall the flux from the inner coil would flow throughthe iron core, some of the flux from the outer coilwould flow through the windings of the coilunderneath.

The origins of the bifilar winding go back to theunipolar drive (see Drive Technologies section,page A23). Rather than have to reverse the currentin one winding, the field may be reversed bytransferring current to a second coil wound in theopposite direction. (Although the two coils arewound the same way, interchanging the ends hasthe same effect.) So with a bifilar-wound motor, thedrive can be kept simple. However, thisrequirement has now largely disappeared with thewidespread availability of the more-efficient bipolardrive. Nevertheless, the two sets of windings dogive us additional flexibility, and we shall see thatdifferent connection methods can be used to givealternative torque-speed characteristics.

If all the coils in a bifilar-wound motor are broughtout separately, there will be a total of 8 leads (seeFig. 1.13). This is becoming the most commonconfiguration since it gives the greatest flexibility.However, there are still a number of motorsproduced with only 6 leads, one lead serving as acommon connection to each winding in a bifilarpair. This arrangement limits the motors range ofapplication since the windings cannot be connectedin parallel. Some motors are made with only 4leads, these are not bifilar-wound and cannot beused with a unipolar drive. There is obviously noalternative connection method with a 4-lead motor,but in many applications this is not a drawback andthe problem of insulating unused leads is avoided.

Fig. 1.13 Motor lead configurations

angles to each other and only interact in the rotorpole pieces. This is an important feature of thehybrid motor it means that the permanent magnetin the rotor does not see the alternating field fromthe windings, hence it does not produce ademagnetizing effect. Unlike the DC servo motor, itis generally impossible to de-magnetize a steppermotor by applying excess current. However, toomuch current will damage the motor in other ways.Excessive heating may melt the insulation or thewinding formers, and may soften the bondingmaterial holding the rotor laminations. If thishappens and the laminations are displaced, theeffects can be the same as if the rotor had beende-magnetized

Fig. 1.14 Longitudinal section through singlestack motor

4-lead 5-lead 6-lead 8-lead

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Motor Technologies

The forcer is equipped with 4 pole pieces eachhaving 3 teeth. The teeth are staggered in pitchwith respect to those on the platen, so thatswitching the current in the coils will bring the nextset of teeth into alignment. A complete switchingcycle (4 full steps) is equivalent to one tooth pitchon the platen. Like the rotary stepper, the linearmotor can be driven from a microstep drive. In thiscase, a typical linear resolution will be 12,500 stepsper inch.

The linear motor is best suited for applications thatrequire a low mass to be moved at high speed. In aleadscrew-driven system, the predominant inertia isusually the leadscrew rather than the load to bemoved. Hence, most of the motor torque goes toaccelerate the leadscrew, and this problembecomes more severe the longer the travelrequired. Using a linear motor, all the developedforce is applied directly to the load and theperformance achieved is independent of the lengthof the move. A screw-driven system can developgreater linear force and better stiffness; however,the maximum speed may be as much as ten timeshigher with the equivalent linear motor. Forexample, a typical maximum speed for a linearmotor is 100 in/sec. To achieve this with a 10-pitchballscrew would require a rotary speed of 6,000rpm. In addition, the linear motor can travel up to12 feet using a standard platen.

How the Linear Motor WorksThe forcer consists of two electromagnets (A and B)and a strong rare earth permanent magnet. Thetwo pole faces of each electromagnet are toothedto concentrate the magnetic flux. Four sets of teethon the forcer are spaced in quadrature so that onlyone set at a time can be aligned with the platenteeth.

The magnetic flux passing between the forcer andthe platen gives rise to a very strong force ofattraction between the two pieces. The attractiveforce can be up to 10 times the peak holding forceof the motor, requiring a bearing arrangement tomaintain precise clearance between the pole facesand platen teeth. Either mechanical roller bearingsor air bearings are used to maintain the requiredclearance.

When current is established in a field winding, theresulting magnetic field tends to reinforcepermanent magnetic flux at one pole face andcancel it at the other. By reversing the current, thereinforcement and cancellation are exchanged.Removing current divides the permanent magneticflux equally between the pole faces. By selectivelyapplying current to phase A and B, it is possible toconcentrate flux at any of the forcers four polefaces. The face receiving the highest fluxconcentration will attempt to align its teeth with theplaten. Fig. 1.17 shows the four primary states orfull steps of the forcer. The four steps result inmotion of one tooth interval to the right. Reversingthe sequence moves the forcer to the left.

adding further magnet sections or stacks to thesame shaft (Fig. 1.15). A second stack will enabletwice the torque to be produced and will double theinertia, so the torque-to-inertia ratio remains thesame. Hence, stepper motors are produced insingle-, two- and three-stack versions in eachframe size.

Fig. 1.15 Three-stack hybrid stepping motor

As a guideline, the torque-to-inertia ratio reduces bya factor of two with each increase in frame size(diameter). So an unloaded 34-size motor canaccelerate twice as rapidly as a 42-size, regardlessof the number of stacks.

Linear Stepping Motors

Fig. 1.16 Linear stepping motor

Platen Teeth

Field Windings

Platen

Phase AElectromagnet

Forcer

PermanentMagnet

BBAAPole Faces

SN

{

1 2 1 2

{ { {

AirGap

Phase BElectromagnet

The linear stepper is essentially a conventionalrotary stepper that has been unwrapped so that itoperates in a straight line. The moving componentis referred to as the forcer and it travels along afixed element or platen. For operational purposes,the platen is equivalent to the rotor in a normalstepper, although it is an entirely passive deviceand has no permanent magnet. The magnet isincorporated in the moving forcer together with thecoils (see Fig. 1.16).

A10

Motor TechnologiesStep Motor CharacteristicsThere are numerous step motor performancecharacteristics that warrant discussion. However,well confine ourselves to those traits with thegreatest practical significance.

Fig. 1.18 illustrates the static torque curve of thehybrid step motor. This relates to a motor that isenergized but stationary. It shows us how therestoring torque varies with rotor position as it isdeflected from its stable point. Were assuming thatthere are no frictional or other static loads on themotor. As the rotor moves away from the stableposition, the torque steadily increases until itreaches a maximum after one full step (1.8). Thismaximum value is called the holding torque and itrepresents the largest static load that can beapplied to the shaft without causing continuousrotation. However, it doesnt tell us the maximumrunning torque of the motor this is always lessthan the holding torque (typically about 70%).

Fig. 1.18 Static torque-displacementcharacteristic

Repeating the sequence in the example will causethe forcer to continue its movement. When thesequence is stopped, the forcer stops with theappropriate tooth set aligned. At rest, the forcerdevelops a holding force that opposes any attemptto displace it. As the resting motor is displaced fromequilibrium, the restoring force increases until thedisplacement reaches one-quarter of a toothinterval. (See Fig. 1.18.) Beyond this point, therestoring force drops. If the motor is pushed overthe crest of its holding force, it slips or jumps rathersharply and comes to rest at an integral number oftooth intervals away from its original location. If thisoccurs while the forcer is travelling along the platen,it is referred to as a stall condition.

Fig. 1.17 The four cardinal states or full steps ofthe forcer

SN

SN

SN

B Aligned

A Aligned

B Aligned

SN

Flux LinesDirection of MMF due to electromagnet

A Aligned

Phase BPhase A

1

2

2

1To

rque

Cloc

kwis

eCo

unte

r Clo

ckw

ise 4 Motor Steps

MaxTorque

UnstableStable StableAngle

As the shaft is deflected beyond one full step, thetorque will fall until it is again at zero after two fullsteps. However, this zero point is unstable and thetorque reverses immediately beyond it. The nextstable point is found four full steps away from thefirst, equivalent to one tooth pitch on the rotor or1/50 of a revolution.

Although this static torque characteristic isnt agreat deal of use on its own, it does help explainsome of the effects we observe. For example, itindicates the static stiffness of the system, (i.e.,how the shaft position changes when a torque loadis applied to a stationary motor). Clearly the shaftmust deflect until the generated torque matches theapplied load. If the load varies, so too will the staticposition. Non-cumulative position errors willtherefore result from effects such as friction or out-of-balance torque loads. It is important toremember that the static stiffness is not improvedby using a microstepping drivea given load on theshaft will produce the same angular deflection. Sowhile microstepping increases resolution andsmoothness, it may not necessarily improvepositioning accuracy.

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Motor TechnologiesUnder dynamic conditions with the motor running,the rotor must be lagging behind the stator field if itis producing torque. Similarly, there will be a leadsituation when the torque reverses duringdeceleration. Note that the lag and lead relate onlyto position and not to speed. From the statictorque curve (Fig. 1.18), clearly this lag or leadcannot exceed two full steps (3.6) if the motor is toretain synchronism. This limit to the position errorcan make the stepper an attractive option insystems where dynamic position accuracy isimportant.

When the stepper performs a single step, thenature of the response is oscillatory as shown inFig. 1.19. The system can be likened to a mass thatis located by a magnetic spring, so the behaviorresembles the classic mass-spring characteristic.Looking at it in simple terms, the static torque curveindicates that during the step, the torque is positiveduring the full forward movement and so isaccelerating the rotor until the new stable point isreached. By this time, the momentum carries therotor past the stable position and the torque nowreverses, slowing the rotor down and bringing itback in the opposite direction. The amplitude,frequency and decay rate of this oscillation willdepend on the friction and inertia in the system aswell as the electrical characteristics of the motorand drive. The initial overshoot also depends onstep amplitude, so half-stepping produces lessovershoot than full stepping and microstepping willbe better still.

Fig. 1.19 Single step response

Attempting to step the motor at its naturaloscillation frequency can cause an exaggeratedresponse known as resonance. In severe cases,this can lead to the motor desynchronizing orstalling. It is seldom a problem with half-stepdrives and even less so with a microstepper. Thenatural resonant speed is typically 100-200 fullsteps/sec. (0.5-1 rev/sec).

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Under full dynamic conditions, the performance ofthe motor is described by the torque-speed curve asshown in Fig. 1.20. There are two operating ranges,the start/stop (or pull in) range and the slew (or pullout) range. Within the start/stop range, the motor canbe started or stopped by applying index pulses atconstant frequency to the drive. At speeds within thisrange, the motor has sufficient torque to accelerateits own inertia up to synchronous speed without theposition lag exceeding 3.6. Clearly, if an inertial loadis added, this speed range is reduced. So the start/stop speed range depends on the load inertia. Theupper limit to the start/stop range is typically between200 and 500 full steps/sec (1-2.5 revs/sec).

Fig. 1.20 Start/stop and slew curves

To operate the motor at faster speeds, it isnecessary to start at a speed within the start/stoprange and then accelerate the motor into the slewregion. Similarly, when stopping the motor, it mustbe decelerated back into the start/stop rangebefore the clock pulses are terminated. Usingacceleration and deceleration ramping allowsmuch higher speeds to be achieved, and inindustrial applications the useful speed rangeextends to about 3000 rpm (10,000 full steps/sec).Note that continuous operation at high speeds isnot normally possible with a stepper due to rotorheating, but high speeds can be used successfullyin positioning applications.

The torque available in the slew range does notdepend on load inertia. The torque-speed curve isnormally measured by accelerating the motor up tospeed and then increasing the load until the motorstalls. With a higher load inertia, a loweracceleration rate must be used but the availabletorque at the final speed is unaffected.

Torq

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Steps per second

Start/Stop

Range

SlewRange

Slew Curve

Start/Stop CurveHoldingTorque

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Motor TechnologiesCommon Questions and AnswersAbout Step Motors

1. Why do step motors run hot?Two reasons: 1. Full current flows through themotor windings at standstill. 2. PWM drivedesigns tend to make the motor run hotter.Motor construction, such as laminationmaterial and riveted rotors, will also affectheating.

2. What are safe operating temperatures?The motors have class B insulation, which israted at 130C. Motor case temperatures of90C will not cause thermal breakdowns.Motors should be mounted where operatorscannot come into contact with the motor case.

3. What can be done to reduce motor heating?Many drives feature a reduce current atstandstill command or jumper. This reducescurrent when the motor is at rest withoutpositional loss.

4. What does the absolute accuracy specificationmean?This refers to inaccuracies, non-cumulative,encountered in machining the motor.

5. How can the repeatability specification bebetter than that of accuracy?Repeatability indicates how precisely aprevious position can be re-obtained. Thereare no inaccuracies in the system that affect agiven position, returning to that position, thesame inaccuracy is encountered.

6. Will motor accuracy increase proportionatelywith the resolution?No. The basic absolute accuracy andhysteresis of the motor remain unchanged.

7. Can I use a small motor on a large load if thetorque requirement is low?Yes, however, if the load inertia is more thanten times the rotor inertia, cogging andextended ringing at the end of the move will beexperienced.

8. How can end of move ringing be reduced?Friction in the system will help damp thisoscillation. Acceleration/deceleration ratescould be increased. If start/stop velocities areused, lowering or eliminating them will help.

9. Why does the motor stall during no loadtesting?The motor needs inertia roughly equal to itsown inertia to accelerate properly. Anyresonances developed in the motor are at theirworst in a no-load condition.

10. Why is motor sizing important, why not just gowith a larger motor?If the motors rotor inertia is the majority of theload, any resonances may become morepronounced. Also, productivity would suffer asexcessive time would be required to acceleratethe larger rotor inertia. Smaller may be better.

11. What are the options for eliminatingresonance?This would most likely happen with full stepsystems. Adding inertia would lower theresonant frequency. Friction would tend to

dampen the modulation. Start/stop velocitieshigher than the resonant point could be used.Changing to half step operation would greatlyhelp. Ministepping and microstepping alsogreatly minimize any resonant vibrations.Viscous inertial dampers may also help.

12. Why does the motor jump at times when it'sturned on?This is due to the rotor having 200 naturaldetent positions. Movement can then be 3.6in either direction.

13. Do the rotor and stator teeth actually mesh?No. While some designs used this type ofharmonic drive, in this case, an air gap is verycarefully maintained between the rotor and thestator.

14. Does the motor itself change if a microsteppingdrive is used?The motor is still the standard 1.8 stepper.Microstepping is accomplished byproportioning currents in the drive (higherresolutions result). Ensure the motorsinductance is compatible.

15. A move is made in one direction, and then themotor is commanded to move the samedistance but in the opposite direction. Themove ends up short, why?Two factors could be influencing the results.First, the motor does have magnetic hysteresisthat is seen on direction changes. This is in thearea of 0.03. Second, any mechanicalbacklash in the system to which the motor iscoupled could also cause loss of motion.

16. Why are some motors constructed as eight-lead motors?This allows greater flexibility. The motor can berun as a six-lead motor with unipolar drives.With bipolar drives, the windings can then beconnected in either series or parallel.

17. What advantage do series or parallelconnection windings give?With the windings connected in series, low-speed torques are maximized. But this alsogives the most inductance so performance athigher speeds is lower than if the windingswere connected in parallel.

18. Can a flat be machined on the motor shaft?Yes, but care must be taken to not damagethe bearings. The motor must not bedisassembled. Compumotor does not warrantythe users work.

19. How long can the motor leads be?For bipolar drives, 100 feet. For unipolardesigns, 50 feet. Shielded, twisted pair cablesare required.

20. Can specialty motors, explosion-proof,radiation-proof, high-temperature, low-temperature, vacuum-rated, or waterproof, beprovided?Compumotor is willing to quote on mostrequirements with the exception of explosionproof.

21. What are the options if an explosion-proofmotor is needed?Installing the motor in a purged box should beinvestigated.

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Motor Technologies

This design was quickly improved, and by the endof the 19th century the design principles of DCmotors had become well established.

About that time; however, AC power supplysystems came into general use and the popularityof the DC motor declined in favor of the lessexpensive AC induction motor. More recently, theparticular characteristics of DC motors, notably highstarting torque and controllability, have led to theirapplication in a wide range of systems requiringaccurate control of speed and position. Thisprocess has been helped by the development ofsophisticated modern drive and computer controlsystems.

PrinciplesIt is well known that when a current-carryingconductor is placed in a magnetic field, itexperiences a force (Fig. 1.22).

Fig. 1.22 Force on a conductor in amagnetic field

DC Brush MotorsThe history of the DC motor can be traced back tothe 1830s, when Michael Faraday did extensivework with disc type machines (Fig. 1.21).

Fig. 1.21 Simple disc motor

The force acting on the conductor is given by:

F = I x B

where B = magnetic flux density and I = current

If this single conductor is replaced by a largenumber of conductors (i.e., a length of wire iswound into a coil), the force per unit length isincreased by the number of turns in the coil. This isthe basis of a DC motor.

Practical ConsiderationsThe problem now is that of using this force toproduce the continuous torque required in apractical motor.

To achieve maximum performance from the motor,the maximum number of conductors must beplaced in the magnetic field, to obtain the greatestpossible force. In practice, this produces a cylinderof wire, with the windings running parallel to the axisof the cylinder. A shaft is placed down this axis toact as a pivot, and this arrangement is called themotor armature (Fig. 1.23).

Fig. 1.23 DC motor armature

This is achieved by constructing the armature as aseries of small sections connected in sequence tothe segments of a commutator (Fig 1.24). Electricalconnection is made to the commutator by means oftwo brushes. It can be seen that if the armaturerotates through 1/6 of a revolution clockwise, thecurrent in coils 3 and 6 will have changed direction.As successive commutator segments pass thebrushes, the current in the coils connected to thosesegments changes direction. This commutation orswitching effect results in a current flow in the

As the armature rotates, so does the resultantmagnetic field. The armature will come to rest withits resultant field aligned with that of the stator field,unless some provision is made to constantlychange the direction of the current in the individualarmature coils.

CommutationThe force that rotates the motor armature is theresult of the interaction between two magneticfields (the stator field and the armature field). Toproduce a constant torque from the motor, thesetwo fields must remain constant in magnitude andin relative orientation.

Fig. 1.24 Electrical arrangement of the armature

N S

Conductive Disc

BrushMagnet

Force (F)

Magnetic Field (B)

ConductorCarryingCurrent (I)(Into Page)

Force on Conductor F = I x B

ResultantField Due toArmatureCurrent

Shaft

Armature

Directionof CurrentInto PageStator Field

2

1 3

4

5

6

CurrentIn Out

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Motor Technologiesarmature that occupies a fixed position in space,independent of the armature rotation, and allowsthe armature to be regarded as a wound core withan axis of magnetization fixed in space. This givesrise to the production of a constant torque outputfrom the motor shaft.

The axis of magnetization is determined by theposition of the brushes. If the motor is to have similarcharacteristics in both directions of rotation, thebrush axis must be positioned to produce an axis ofmagnetization that is at 90 to the stator field.

DC Motor TypesSeveral different types of DC motor are currentlyin use.

Iron cored. (Fig. 1.25). This is the most commontype of motor used in DC servo systems. It is madeup of two main parts; a housing containing the fieldmagnets and a rotor made up of coils of wirewound in slots in an iron core and connected to acommutator. Brushes, in contact with thecommutator, carry current to the coils.

Fig. 1.25 Iron-cored motor

Brushless. The major limiting factor in theperformance of iron-cored motors is internalheating. This heat escapes through the shaft andbearings to the outer casing, or through the airgapbetween the armature and field magnets and fromthere to the casing. Both of these routes arethermally inefficient, so cooling of the motorarmature is very poor.

Fig. 1.28 Brushless motor

In the brushless motor, the construction of the ironcored motor is turned inside out, so that the rotorbecomes a permanent magnet and the statorbecomes a wound iron core.

The current-carrying coils are now located in thehousing, providing a short, efficient thermal path tothe outside air. Cooling can further be improved byfinning the outer casing and blowing air over it ifnecessary (to effectively cool an iron-cored motor, itis necessary to blow air through it.) The ease ofcooling the brushless motor allows it to produce amuch higher power in relation to its size.

The other major advantage of brushless motors istheir lack of a conventional commutator and brushgear. These items are a source of wear andpotential trouble and may require frequentmaintenance. By not having these components, thebrushless motor is inherently more reliable and canbe used in adverse environmental conditions.

To achieve high torque and low inertia, brushlessmotors do require rare earth magnets that aremuch more expensive than conventional ceramicmagnets. The electronics necessary to drive abrushless motor are also more complex than for abrush motor. A more thorough explanation ofbrushless motors is provided on page A17.

Losses in DC MotorsDC motors are designed to convert electrical powerinto mechanical power and as a consequence ofthis, during periods of deceleration or if externallydriven, will generate electrical power. However, allthe input power is not converted into mechanicalpower due to the electrical resistance of thearmature and other rotational losses. These lossesgive rise to heat generation within the motor.

S

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BackironReturnPath

StatorLam Teeth

Magnets

Windings

CommutatorBrushes

Rotor Winding

Stator Magnets

Moving coil. There are two principle forms of thistype of motor. 1. The printed motor (Fig. 1.26),using a disc armature. 2. The shell type armature(Fig. 1.27).

Since these types of motors have no moving iron intheir magnetic field, they do not suffer from ironlosses. Consequently, higher rotational speeds canbe obtained with low power inputs.

Fig. 1.26 Disc-armature printed motor

Diagrams courtesy of Electro-Craft Ltd.

S

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MotionAir gap

Magnet pole

Flux pathCoreArmature

(Hollow cup, shapedconductor array)

Fig. 1.27 Shell-armature motor

Permanent magnet(8 pole)

Motion

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Motor TechnologiesShort circuit currents. As the brushes slide overthe commutator, the brush is in contact with twocommutator segments for a brief period. During thisperiod, the brush will short out the coil connectedto those segments (Fig. 1.30). This conditiongenerates a torque that opposes the main drivingtorque and increases with motor speed.

Fig. 1.30 Generation of short-circuit currents

All these losses will contribute heat to the motorand it is this heating that will ultimately limit themotor application.

Other Limiting ConsiderationsTorque ripple. The requirement for constant torqueoutput from a DC motor is that the magnetic fieldsdue to the stator and the armature are constant inmagnitude and relative orientation, but this ideal isnot achieved in practice. As the armature rotates,the relative orientation of the fields will changeslightly and this will result in small changes in torqueoutput called torque ripple (Fig. 1.31).

Fig. 1.31 Torque ripple components

This will not usually cause problems at high speedssince the inertia of the motor and the load will tendto smooth out the effects, but problems may ariseat low speeds.

Motors can be designed to minimize the effects oftorque ripple by increasing the number of windings,or the number of motor poles, or by skewing thearmature windings.

Motor losses can be divided into two areas: Thosethat depend on the load and those that depend onspeed (Fig. 1.29).

Fig. 1.29 Losses in a DC motor

Winding losses. These are caused by the electricalresistance of the motor windings and are equal toI2R (where I = armature current and R = armatureresistance).

As the torque output of the motor increases, Iincreases, which gives rise to additional losses.Consideration of winding losses is very importantsince heating of the armature winding causes anincrease in R, which results in further losses andheating. This process can destroy the motor if themaximum current is not limited. Furthermore, athigher temperatures, the field magnets begin tolose their strength. Hence, for a required torqueoutput the current requirement becomes greater.

Brush contact losses. These are fairly complex toanalyze since they depend upon several factors thatwill vary with motor operation. In general