DMIA completely newgeneration ofmedium-sizedDC motors

DC innovations offer new opportunities

2ABBs new generation of DC motors turns

many ingrained concepts upside down. Thanks

to creative innovations and state-of-the-art

computerized optimization of technical solu-

tions that earlier were considered to have

reached the design limits, a completely new

generation of DC motors has evolved. They

embody a number of positive characteristics,

which previously could not be combined:

High output and small dimensions

High output over a wide speed range

Smooth running at low speeds and low

moment of inertia

Benefits of DC and the minimum of

maintenance

The new generation of DC motors offers com-

pletely new opportunities for improving pro-

ductivity as a result of the substantially faster

speed control. At the same time, the investment

costs are lowered. Thanks to the precise opti-

mization of the electrical and mechanical

characteristics and the wide speed range, over-

sizing of motor drives to achieve the desired

speed range is unnecessary. It is no exaggera-

tion to say that the DMI motors belong to a

generation offering a completely new perform-

ance and new opportunities.

DMI motors peak performance

kW

Highertorquequality atlow speed

3Higher powerat top speed

Higher powerand torque

Higherspeed

DMI

r/min

Diagram showing the performance (blue curve) of the DMI motorscompared with that of other DC motors of well-known makes.

4DMI motors with unsurpassedperformanceThe DMI motors represent a unique productin the world, because all their characteristics output, torque, speed range and top speed rank among the absolutely best available inthe market. No compromise has been madehere. Dedicated research and development(R&D) work has been undertaken to achievethis position. A team of engineers possessingmore than 200 man-years of experience of DCmotor drive systems, for example, participatedin the electrical design work. They had at theirdisposal all of ABBs high-tech R&D resources.

The development work during the design ofthe electrical system was focused on factorsthat increase the commutation margin. The sizeof the commutation margin has in fact been fora long time a measure of the quality of a DCmotor, in view of its great influence on themaintenance needs. The goal that the motorwas to possess a large commutation marginwas therefore self-evident.

New ways of tackling old problemsgave resultsWhen a new series of motors is being design-ed, you must not stick to old ways of thinking,but instead break down the paradigms and beaware that each weakness and limitationpresent a big opportunity for improvement.By applying new design ideas (patentspending) together with modern FEM techniquefor an in-depth investigation of importantissues of an electromagnetic, thermodynamicand mechanical nature, we achieved our goals:high output and high torque in a small motorframe size. This was combined in a uniqueway with a large commutation margin and avery long thermal life. Additional benefits ofthe DMI motor include a low moment of iner-tia and a large speed range through field weak-ening without any drop in output. Advanced,comprehensive testing verified the motorscharacteristics.

DMI motors- innovations beyond the limits

The performance of DC motors has undergone rapid improvements during this century, particularly over the past 30 years.Depending on the level of technology and customer value philosophy, different motor manufacturers have reached differentcompromises. The performance of their motors has consequently varied.

Those manufacturers who have been able to achieve a high output and torque have frequently been considered to bemarket leaders. The coupling between low commutation stresses and reliable service, however, has frequently been dis-regarded. Motor types possessing a large commutation margin have had a rather moderate output and torque, which limitedtheir competitiveness, except in those cases where the end user requires a large speed range without any drop in the output.Other motor manufacturers have focused on maximum speed.

Substantial R&D wasmade to improve the cooling

and the magnetic circuit.

5

6Higher output and torqueSalient features of the DMI motors are theirvery high output and torque in relation to theframe size. A number of new solutions (patentsapplied for several of them by ABB) havetogether given the DMI motors such a superiorperformance that they are in a class of theirown in the DC market.

The development work on the stator, forexample, has provided more space for thewindings and led to a more uniform tempera-ture distribution due to a more compact coildesign and improved manufacturing processes.

The biggest difference, however, has beenachieved in the armature. Arranging the cool-ing ducts below the winding slots gives firstand foremost a fully symmetrical distributionof the magnetic flux path in the armature. Inaddition, there is a minimal intrusion of thecooling ducts into the magnetic flux path.The efficiency of the cooling ducts couldconsequently be strikingly improved as a resultof them being moved closer to the windingslots. At the same time, their cooling areacould be enlarged. Combining in this wayincreased cooling with a simultaneous im-provement of the magnetic flux circuit wassomething that was impossible in the past. Theimprovement of the magnetic flux paths in thearmature was also followed up with a carefuloptimization of the stator.

Location of the coolingducts opposite and close tothe winding slots gives acompletely symmetricaldistribution of the mag-netic flux and, at thesame time, improves thecooling.

DMI motors- innovations beyond the limits, continued

Higher output at top speedWhen large speed ranges are required, mo-tors that can be shunt-controlled without anydrop in their output give several benefits. Itis no longer necessary to over-size the motorand the converter. In addition, the feedingback of reactive power to the network isreduced.

The reduction of the commutation stresseshas given the DMI motor outstanding charac-teristics in the shunting range. The full out-put can therefore be maintained up to veryhigh speeds. The more efficient coolingmakes this possible, because the size of thewinding slots can be reduced, which in turnprovides more space for magnetic material.The comprehensive optimization of the en-tire magnetic circuit and the perfect magneticsymmetry in the armature brought about bythe location of the cooling ducts have signifi-cantly contributed to a further improvementof the motors characteristics.

The cooling of the arma-ture coil-ends on the hotair side was also signifi-cantly improved by usingaluminium for the coilsupport and giving it ribs.

The poles and stator core have also been designed to givean optimum magnetic circuit.

7Oblique coil slots give theDMI motor excellent low-speed characteristics andalso a lower noise level.

Higher speedThe fundamental qualities of the design ofthe DMI motors have led to a marked in-crease in the top speed without this affectingthe service reliability. Since the armaturewinding slots are radially small and themagnetic circuit is amply dimensioned, thecore and winding losses are kept at a lowlevel also at high speeds.

The design work was also focused on in-creasing the stability of the commutator andreducing its diameter with a lower peripheralspeed as result to ensure proper functioningof the brushes at the highest speeds. In ad-dition, vibrations are kept at a low level. Thisis accomplished by preventing movements inthe coil-ends by means of robust supportingrings below the armature coil-ends and byusing a massive shaft to prevent its deflection.

Higher torque quality at low speedIf smooth running free from jerks at lowspeeds is to be obtained, the magnetizationof the armature core laminations must be uni-form. The built-in magnetic polarization, anormal characteristic of electrical steel, resultsin jerky running at low speeds, if this cannotbe suppressed. The design of the DMI motorcompletely eliminates this phenomenon, partlyas a result of a special manufacturing process,which levels out the variations in the armaturecore laminations, and partly by means of theoblique configuration of the armature coil slots.This is essential to obtain a uniform and 100per cent controlled running at the very lowestspeeds.

Faster acceleration and reversalBecause the armature normally accounts for asmuch as 50 per cent of the moment of inertiaof the complete shaft system, i.e., motor/coupling/gearbox/driven machine, it is veryimportant to reduce the armatures moment ofinertia in order to achieve faster speed control.

The DMI motors have a very low moment ofinertia, since their armature has a small diame-ter in relation to the torque produced.

With the markets best torque/shaft heightratio, a high top speed and an armature with avery low moment of inertia, the faster acceler-ation and reversal of the DMI motors offerABBs customers new opportunities for pro-ductivity gains.

The commutator has a small diameter and consequent-ly a low peripheral speed. The brushes will thereforefunction properly at high speeds.

8Armaturecurrent

DMI motors

Other motorsInsufficientcommutation

DMI motors- another word for reliability

Large commutation margin reducesstressesA large commutation margin is important toobtain reliability and to minimize the need formaintenance. The commutation margin isaffected by the type of converter, field exciterdesign and normal duty parameters as currentripple, vibrations, temperature, load and cool-ing air contaminants. The DMI motors are spe-cially designed and tested to handle all thesefactors. The design features adopted havemade this possible. A DC motor subject toa high commutation stress can only run withspecial brush grades leaving no or a lowmargin to adapt the brush grade to localconditions on site.

The unusually large commutation margin ofthe DMI motors, however, covers not only theapplication parameters mentioned above. Themotors are also capable of running with brushgrades suitable for different environmentalconditions on site, thus minimizing the needfor maintenance.

The outstanding characteristics of the DMI motor are the result of the dedicated, systematic development work undertaken byABBs creative researchers, designers and production engineers. With the help of new approaches and state-of-the art designtools, ABB has tackled classic problems and succeeded in significantly improving what appears to be a mature product.Reliability has naturally been a top priority in this work.

Comprehensive tests verify the reliabilityof the motorsEvery motor type has been subject to an ex-tended type test procedure, where the motorbehaviour is measured and calculated. Thesetests include vibration measurements, noiselevel measurements, recording of characteristiccurves, commutation tests and temperaturemeasurements.

The carbon dust test is another importanttest, which the motors have undergone. Duringthis test the interior of the motor is intentional-ly contaminated with a quantity of conductingcarbon dust corresponding to the brush wearafter many years of service. After the motorshave been stopped, it is possible to see thepaths taken by the dust and the places whereharmful deposits of dust have settled in themotors. The results of these tests led to designmodifications, which ensure that the insulationresistance will lie on a high level also aftermany years of service.

The commutation margin of DMI is sufficient tohandle additional stress.

9The insulation system wasimproved as a result of

experiences gained frompollution tests.

10

DMI motors- another word for reliability, continued

Well-proven insulation systemThe insulating material has been chosen togive an extremely long thermal life. The insu-lation system is built up from insulating mate-rials having different properties to maximizethe reliability. For example, material with ahigh temperature index is used where thewinding temperature is high, while mechani-cally stronger material is used in places whereso required.

The DMI motors are designed as standardfor class H. This is possible because they haveinsulating material with a temperature indexway above the limit of class H. The built-inextra margin is substantial, which ensures avery long life. In fact, the temperature margineven surpasses that of the motor series thatpreceded the DMI motors. The insulation ofthe DMI motors can consequently be expect-ed to be reliable for decades.

Not commonly known but very importantfor the life is the fact that ABB always deter-mines the temperature margin by taking intoaccount the maximum real temperature rise inservice. The real temperature rise can differsubstantially from that determined accordingto IEC 34-1, which specifies lower demandsand allows the temperature to be measuredquite a while after the motor has beenstopped.

In addition, control of hot spots is furtherimproved due to the new cooling system ofthe DMI motor series.

FEM simulations to optimize the designTo assure reliable service, ABB has frequentlyused FEM simulations in the design work ofthe DMI motors for: Electromagnetic circuit Thermal calculations Mechanical dimensioning Cooling system

Temperatures in the windings and magneticfluxes in the iron core both depend on theconfiguration of the iron core in the stator andarmature. They have therefore been evaluatedvery carefully in order to optimize the configu-ration of the iron core. The evaluations havebeen made with FEM tools for thermal calcula-tions and for flux calculations. These calcula-tions have resulted in a stator and an armaturecore that can give a high output without mag-netic saturation.

Optimization of iron core using a FEM tool for fluxcalculations.

11

Probability index

500

400

300

200

100

0

After modification

Before modification

6 5 4 3 2 1 7

Failure modes

LCA studies for low environmental impactThe DMI motors have also been designed togive a low impact on the environment. An LCA(Life Cycle Assessment) analysis was used asguidance in the design work. The followingparameters were considered: Environmental impact during production Avoidance of the use of materials critical to

the environment Efficiency Life Recycling

The total efficiency of a torque and speed-controlled drive is a function of many para-meters supported by the DMI motor design.These include low fan power, low momentof inertia, which reduces the acceleration/deceleration energy, wide speed range andhigh maximum speed, which can be used forgearbox optimization. If requested, ABB canfurther improve the efficiency by means ofoptimization for each order.

Predictable maintenanceA low level of maintenance is an importantcustomer requirement. But it is just as import-ant for the customer to be able to draw upreliable plans for the maintenance intervalswithout any unforeseen disturbances occurringbetween them. The DMI motor has not onlybeen designed to reduce the maintenanceneeds. Its built-in margins increase the reliabili-ty and the possibility to predict with certaintythe maintenance needs. The DMI motors havethe following features: Large commutation margin

Optimum brush grade can be selected Long brush wear length Very good commutator shape stability

Low brush wear Small commutator diameter

Low brush wear Small sealing gaps in the bearings

No risk of grease leakage into the motor(provided the correct grade of grease isused). In addition, the bearings resistanceto contaminants increases

Bearings with long lubrication intervals Filter with high degree of filtration in the

cooling system Long cleaning intervals

High resistance to contaminants Long cleaning intervals

Brush grade optimizationto achieve low wear isnormally only possible inmotors with a sufficientcommutation margin.

FMEA used to achieve high qualityFailure mode and effect analysis (FMEA) is amethod used for the systematic identificationof all steps needed to meet quality targetsand achieve maximum reliability. FMEA wasapplied in both the design and the manu-facturing process for the DMI motor series toachieve ABBs high quality targets and meetcustomer expectations.

FMEA diagram showing how the reliability of compon-ents and their function has been improved from theoriginal to the final design compared with the target.

12

DMI motors flexibility and well-designed parts

Flexible terminal box

The terminal box can be mounted on the top

or long sides of the motor

The cable entry can be located in 12 different

positions and altered, if necessary, on site

The detachable frame facilitates cable installation

also when the motor is set up in a confined space

Bearings with efficient lubrication

Relubrication of the motor required only

once a year

Efficient lubrication grease forced through

the bearing to give maximum bearing life

Grease slinger and improved bearing seals

reduce the risk of grease penetrating into

the motor

Grease nipple easily accessible on

the bearing endshield

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Low noise level

Designed to give low magnetic ripple

Oblique armature slots

Stable stator frame with large margin to the natural frequency

Low-noise fan due to the screened inlet and high efficiency

The cooling air inlet and outlet can be provided with silencers, if necessary

Easily installed speed devices

Minimum length

Insulated coupling for the shaft

no bearing currents

Simple and quick replacement on site

of the speed device

The installation fittings are simple to

adapt to speed devices of different types

Efficient cooling fan

Low fan powers

Fan can be fitted in 6 different positions,

which offers good installation possibilities

The filter has a high cleaning capacity and a long life

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DMI motors- offer new opportunities

The DMI motors set a new standard for medium-sized DC machines when it comes to their dimensionsand performance. This presents new opportunities to raise the productivity of the driven equipment.The outstanding performance of the motors can also lower the costs of both the machine builder andthe end user. How the new opportunities afforded by the DMI motors can be utilized depends on theapplication. A few examples from different industries are described here.

Container cranesThe hoist machineryof a container cranetoday is runningabout half the timewith a load and halfthe time unloaded.The weight of theload varies between

15 to 75 tonnes, depending on whether thespreader is carrying a fully loaded container orif the spreader is empty. Because the speed ofthe hoist motion is adapted to the weight ofthe load, the ratio between the highest and thelowest speed will depend on the drive motorsshunt range. With the large shunt range offeredby the DMI motor it is possible to increase thespeed range. This results in shorter cycle timesand higher productivity.

The hoist drive on a crane is usually deter-mined by the top speed and acceleration/deceleration torque requirements. Themoments of inertia of the motor, gearboxand brakes influence to a large extent thedimensioning of the drive system. The DMImotor has an extremely low moment of inertia,resulting in lower max. torque requirements foracceleration/deceleration, and a more efficientdrive system.

The DMI motors offer uniquebenefits for both light and heavy

process industries.

Snow cannons andski liftsThe possibility toeliminate a gearboxand yet maintain anoptimum speed givesnot only a lower in-vestment cost butalso great operating

benefits. The DMI motors have an extremelyhigh maximum speed, which means that thedirectly driven pumps in large snow cannoninstallations can run at the optimum speed.

Ski lifts also preferably require a high maxi-mum speed, and then in combination withcounter-current braking. Here, too, the DMImotor offers a flexible solution.

In addition, due to the location of ski lifts,the electricity supply is usually weak. This nor-mally means that DC drive systems are selectedfor higher outputs. This choice becomes evenmore natural with the DMI motor. Its goodmargins, not least the commutation margin,ensure that the motor can run reliably also inthe event of relatively large disturbances in thesupply network.

1515

Plastic extrudersPlastic extruders arethe most widelyoccurring applicationfor DC motor drives.The reasons for thisare both the largenumbers of plasticextruders in oper-

ation around the world and the fact that DCmotors drive most of them. The dominance ofDC motors is due to the fact that they meet theneed for a high base speed, good speed accu-racy and a large overload capability at a com-petitive price.

Like other DC motors, the DMI motors offerthe possibility of good speed accuracy. Asregards a high base speed, the DMI motorshold a unique position. Their high torque andlarge output per shaft height ensure that theDMI motors can also meet the demand for80 per cent overload for 1 minute with aphysically small motor. This reduces boththe investment and the operating costs forthe complete drive package.

The fact that each motor size (shaft height)includes a large range of core lengths ensuresthat a desired output or torque specificationcan be met with either a long motor having alow shaft height or a short motor having alarger shaft height. The standard range ofmotors and accessories offers great adaptationpossibilities.

Test rigsTest rigs are used inthe automotive indus-try to test engines,gearboxes and otherdrive train compo-nents. Test rigs placespecial demands onthe drive package:

The machine included in the test rig must beable to run as both a motor and a generator.This is something that gives DC technologyan advantage.

In addition, it should be possible to obtain aconstant output over a large speed range andto have a high maximum speed. This is nec-essary to make the drive packages gearboxas small as possible, which is essential if alow moment of inertia is to be achieved.

A good dynamic performance is desirableduring the testing to permit the simulationof fast accelerations and strong braking.The performance of the DMI motors perfect-ly fits the demands made by test rigs.

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A world leader- ABB believes strongly in DC drive systems

A broad line of modern DC motorsABBs line of DC motors covers the outputrange 1 to 3,200 kW, which in terms of torquemeans 5 to 162,000 Nm. This large range iscovered by a number of product families, eachadapted to the demands made by the appli-cations and customers.

The motors in the lower output range matchthe demands made above all by machinebuilders. The motor designs offer great flexibil-ity as to the location of cooler and terminalbox. This offers excellent opportunities to fitthe motors in the overall design of the machineor plant. The manufacturing and the logisticsboth meet the need for extremely short deliv-ery times.

The motors in the medium output rangemeet the demands of both machine buildersand plant suppliers. It is in this range that thenew DMI motors are to be found. Motors in-corporating a lot of innovative ideas and hav-ing an outstanding performance.

The motors in the higher output range, too,offer great flexibility, and there is also a largechoice of standard accessories. Because thesemotors are mainly used in larger plants, thereare great opportunities for customization here.

The shaft height, output and torque of thedifferent product series overlap one another toa certain extent. This gives unusually largeopportunities to find a perfect motor for eachdrive. All the motors have a compact, modulardesign in combination with low noise levels,low vibration levels and high outputs.

For a long time the opinion has been that it is only a matter of time until the AC drive systems will havecompletely replaced DC drive systems. But this has not been the case. DC systems are still competi-tive and the volume has remained relatively constant in the output range over some tens of kW.

Developments are instead pointing towards a situation where the market for torque- and speed-controlled drive systems is in the process of being split up depending on the applications. Thewinners are the suppliers and end users that can best combine AC and DC drive systems.

ABB believes that DC systems have a positive future. The latest development has resulted in newranges of motors, converters and other products having outstanding performances.

Converters for both simple and verydemanding applicationsABB has traditionally always been very strongas supplier of larger drive systems for demand-ing applications, mainly in large plants. Theconverters for this customer category havegreat functionality and a large power range.There is also a very large choice of accessories,software and hardware. User-friendly controlpanels, sophisticated programming tools andI/O functions ensure effective adaptation todifferent applications.

New converter for machine buildersWith DCS 400, ABBs new line of smallerconverters specially developed for machinebuilders, ABB has now gone the whole wayin this product segment. The new converter issimple to use and easy to integrate into amachine design. With the very well designedcommissioning tool, even somebody notspecializing in drive systems can easilycommission the converter in less than 15minutes. The integrated field exciter basedon IGBT technology contributes to the simplehandling of the converter. It is no longernecessary to have separate cables for the fieldsupply or a transformer for the field voltagematching. The installation and commissioningtimes have been substantially reduced, result-ing in a corresponding decrease in costs.

17

ABBs new range of DC products.

Other advanced ABB productsA complete system solution requires more thanjust motors and converters. The power supplyand higher-level control equipment are otherimportant building blocks included in ABBsproduct portfolio and which can form part ofa complete system delivery. In addition, ABBoffers advanced process transducers andsensors, which can lead to significant pro-ductivity gains in different productionlines.

In many applications it is im-portant, for example, to main-tain a constant web or striptension to achieve a high pro-ductivity and ensure a highand uniform product qualityas well as the minimumnumber of web/strip breaks.ABB offers here a line ofload cells based on thePressductor principle. ABBhas recently introduced, forexample, a series of small,easily installed tensiometers.Their design is based on ourcomprehensive experienceof heavy-duty applicationsof large load cells in thepaper and metals indus-tries, where ABBs loadcells have becomemore or lessstandard.

18

Simple to selectA product catalogue is easily accessible onInternet. It is true that it has been simplified,but it is nevertheless sufficient to enable you tomake your first preliminary motor selection. Acomplete printed catalogue can be ordered viaInternet. A form is also available on Internet toenable you to specify your motor require-ments. This is intended mainly for enquiries,but also for use as a technical appendix inconjunction with orders.

Simple to integrateIt is desirable that a designer, who is to inte-grate a motor into a machine design, canquickly obtain detailed information. Such infor-mation about ABBs DC motor programme isavailable on Internet. Dimension drawings,terminal diagrams for standard machines andrecommendations about the design of motorbedplates are also available here.

Simple to commissionFor an experienced electrician it is simple toinstall and commission an ABB motor. Briefinstallation instructions and a detailed main-tenance manual are supplied together with themotor. In addition, information is available inseveral languages on Internet. Our help deskcan give you further support.

Product development is more than just creating products having large and appreciated customervalues. It is also a matter of creating well-organized logistics. This implies above all shorterdelivery times. But it also implies simplicity at all stages from product selection to integration,installation and maintenance. Simplicity is largely a matter of openness in the information flow andmaking the information available. ABB uses the combination of Internet and printed information forboth the newly developed motors and converters and for the rest of ABBs DC programme.

Simplicity- all the way

Readily accessibleinformation makes

life easier for machinebuilders and end users.

Simple to keep in serviceThe maintenance instructions, which areavailable in many languages on Internet and inprinted form in English, provide good supportfor the planning of the maintenance, care andtroubleshooting.

Our help desk is available to providesupport, and ABBs global service networkensures that competent assistance is alwaysavailable within easy reach.

ABB Spare Parts Logistic Centerguarantees fast and reliable availabilityof spare parts throughout the world.

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Building on more than a century of experience in the supply of electricalmachines throughout the world, ABB has become one of the worldsleading producers of DC machines.

ABBs global presence places manufacturing, engineering, marketingand service support within easy reach of customers almost anywhere inthe world. Ensuring that our customers get active support at all stagesof a project, based on specific knowledge of local conditions and re-quirements.

All of which helps ensure that customers will always get the bestsolution from ABB.

ABB MotorsMachines DivisionSE-721 70 Vsters, Sweden

Tel: +46 (0)21-342000Fax: +46 (0)21-182148

Internet www.abb.com/dc/

IntroPeak performanceDiagram

Innovations beyond the limitsReliabilityFlexibilityNew opportunitiesA world leaderSimplicity