d7e faqs

AEXQ0462

© 2009 Caterpillar All Rights Reserved Printed in the USACAT, CATERPILLAR, their respective logos, “Caterpillar Yellow,” the “Power Edge” trade dress as well as corporateand product identity used herein, are trademarks of Caterpillar and may not be used without permission.

THE CAT® D7E WITH ELECTRIC DRIVEFrequently Asked Questions

D7E TRACK-TYPE TRACTOR What Will Our Customers Ask?

3D7E FREQUENTLY ASKED QUESTIONS

What Makes the D7E Innovative from the Inside Out?

10% to 30% lessfuel consumed per hour

Exclusivecenter-post cab with unprecedented all-aroundvisibility, more overall room, lower noise levelsand a tilt feature that provides access to drivesystem components

Simplifiedhydraulics, including a D9-sized single lift cylinder

Modularelectric air conditioning systemthat eliminates long coolant linesand delivers the best performancein a track-type tractor

Grouped service pointsfor fast, convenient service access

50% bettersteering performance

Up to 70% lowerundercarriage owning & operating costswith optional SystemOne™ undercarriage

Up to 50%longer life for the electric drive train

60% fewermoving parts in theelectric drive train

50% lower noise levels

25% morematerial moved per gallon/liter of fuel

10% morematerial moved per hour

35% more visibility

10% lowerlifetime operating costs

Less down timewith no engine belts to replace or adjust

Larger cab with ergonomic controls

Less fluids used

Easy to operatewith low-effort controls

and no shifting

Grade Control Readyfrom the factory

Cat C9.3 enginewith ACERT™ Technology

Electro-hydraulics

Hydraulic demand fan

2

When Caterpillar set out to develop a highly advanced, first-of-its-kind

electric drive track-type tractor, we knew there would be questions.

Customers and dealers would want information that would help them

understand the new technology, how it might affect their businesses and

what inherent benefits it could offer to their day-to-day operations.

To find out what specific things customers would need to know to

understand the technology—and ultimately be driven to purchase the new

machine—we engaged customer and dealer groups throughout the

development process.

We met with separate advisory groups made up of Caterpillar customers and

dealers in various locations throughout North America and Europe. First,

each group received background information on the development of the

machine, how the technologies work, what they mean for businesses and

how they might affect the future evolution of track-type tractor design. We

then followed up with the same groups to identify concerns critical to

machine acceptance.

The following document provides answers to the questions these dealers

and customers identified as most important when considering whether to

purchase the D7E WITH ELECTRIC DRIVE.

We Listened to Our Customers

Electric drive train

Dedicated steering pump

10% to 30%reduction in greenhouse gas (CO2) emissions


How do the operating costs of the D7Ecompare with those of conventionaltractors in its class?

Depending on application and otherfactors, the D7E can reduce lifetimeoperating costs by up to 10 percent.The savings are realized through acombination of factors, including:

• A reduction by as much as25 percent in fuel usage per cubicyard/meter of material moved.

• Longer component operatinglife, particularly for theelectric drive system andSystemOne undercarriage.

• Beltless design—Accessory systemsare electrically powered, so enginebelts, which require frequentadjustment and replacement, andalternators are not needed.

• Extended maintenance intervals—Forexample, the electric drive train oilchange period is up to four timeslonger, depending on application andS•O•SSM sampling results, than thatrecommended for a power shift drivetrain, in part because the mechanicaltorque converter has been eliminated.Dramatic reductions in the number ofgears, bearings and clutches alsoextend filter life.

How does maintenance access on theD7E compare with previous models?

Easy service access to the drive trainsystem is accomplished by tilting thecab. The modular component designmakes swap-outs and repairs easy. TheD7E also features convenient left-hand-side grouped service points, plusextended service intervals, especiallyfor drive train components.

Are there environmental benefits?

With 10 percent to 30 percent lowerfuel usage per hour of operationthan the D7R Series 2, the D7E willdramatically reduce carbon dioxideproduction. Lower power train oilvolume and longer power train oil lifehelp reduce oil disposal issues.

Overall, the new D7E is designed toconsume fewer resources (parts, fluidsand fuel) over its working life than anyother track-type tractor in its class. Theelectric drive system delivers longerservice life than conventional drives.

The D7E also features a proven CatC9.3 engine with ACERT™ Technology.It meets all U.S. EPA Tier 3, EU StageIIIA and Japan MLIT Step 3 regulationswhile delivering reliable performanceand long service life.



Why did Caterpillar develop the D7E?

The Cat® D7E was designed to meet agrowing demand for powerful yet highlymaneuverable track-type tractors.More and more, dozers in the D7 classare called upon for site developmentwork, especially in residentialapplications. These jobs demand amix of straight-ahead dozing powerand tight-quarters maneuverability.

Until now, it has been difficult to findthe right balance between these twocapabilities in a single machine. But byadapting electric drive technology tothe unique requirements of dozerapplications, Caterpillar has developedan all-new class of tractor thatdelivers the best possible balance ofheavy-dozing and fine-gradingperformance. It moves more materialper gallon/liter of fuel while costingless to maintain and service, andmeeting emissions requirements.

What makes the D7E different fromprevious D7 models?

The D7E was completely reengineeredfrom the ground up to take advantageof an all-new electric drive system.The D7E’s electric drive is the mostadvanced electric drive system for atrack-type tractor. The entire machinewas designed around this new drivesystem, with the goal of eliminatingmany of the mechanical componentsthat contribute significantly tooperating and maintenance costs.

The electric drive system also helps tomake the D7E the most fuel-efficientand productive track-type tractor of itssize, with the lowest-ever overalloperating costs in its class.

What separates the D7E fromcompetitive machines of similar sizeand power?

The D7E offers many features that arenot available on any other machine inits class. The most obvious is theelectric drive system, which providesunprecedented productivity, efficiencyand maneuverability.

A dedicated pump for the differentialsteering system, combined withcontinuously variable speedcontrol, provides highly efficient,high-performance steering. Differentialsteering performs at an entirely newlevel on this machine. The continuouslyvariable electric drive train enables alocked-track turn, and the use of adedicated steering pump helps itdeliver full steering speed andpower under a wide variety ofoperating conditions.

Machine balance with and withoutattachments has been optimized aswell. Adding or removing rearattachments will have less effect onthe machine’s center of gravity andoverall balance, giving betterperformance in all implementconfigurations. Ground clearance hasbeen maintained from previous D7models, and a smoother ride helpsmaximize operator productivity.

Overview

D7E FREQUENTLY ASKED QUESTIONS4

> Tilt-cab service access


How does the electric drive systemaffect engine performance?

The D7E electric drive system allowsthe engine to work in a narrow speedrange. The continuously variableelectric drive train can vary its powerdemand with minimal change to theengine speed. That allows othersystems—such as implementhydraulics and steering hydraulics—toprovide consistent performance. Thathelps the engine work more efficiently,which contributes to lower fuel usage.It can also enhance overall engine life.

Is the electric drive system easyto operate?

Because it has no gears to shift, theD7E’s electric drive system is easy tooperate and easy to learn. Newoperators get up to speed quickly, andexperienced operators adapt to iteasily, especially if they have everoperated a machine with ahydrostatic transmission.

The electric drive system deliversprecise, smooth implement control, andit relieves operators of most enginemanagement responsibilities. Thatmakes operation easier and allows theoperators to concentrate on the workbeing done at the blade or ripper.

What are the key benefits of the D7E’selectric drive system?

• Unmatched Efficiency & Versatility—The electric drive system deliversengine power to the groundefficiently, and it provides infinitelyvariable speed control similar to thatof a hydrostatic transmission. As aresult, it delivers both excellentmaneuverability and efficientproduction dozing performance.

In fact, the D7E delivers a quantumleap in overall dozing efficiency,moving 25 percent more cubicyards/meters of material pergallon/liter of fuel than its class-

leading predecessor, the D7R Series2. In utility and finish-gradingapplications, the D7E can deliver aneven greater improvement.

• Fewer Moving Parts, Lower ServiceCosts—The D7E’s electric drive istechnically advanced butmechanically simple when comparedwith conventional drive systems. Ithas 60 percent fewer moving partsthan a mechanical drive system,which means there are fewercomponents to wear out or potentiallybreak down. These components havebeen designed to last up to 50percent longer than a conventionaldrive system working in a similarapplication.

For example, the electric drive systemcontains no friction clutches, whichreduces service requirements. Andbecause many accessory systemsare electrically powered, the D7E isentirely beltless. There are no enginebelts to break, wear or replace,which improves operational reliabilityand further lowers service costs.

• Improved Fuel Consumption—TheD7E delivers a 10 percent to 30percent improvement in fuelconsumption (as measured ingallons/liters of fuel burned per hourof operation) compared with theprevious model, while delivering a 10percent increase in productivity(cubic yards/meters per hour) inmost applications.

• Dramatically Improved SteeringPerformance—The combination ofelectric drive and Caterpillar’s provendifferential steering system alsodelivers 50 percent more steeringperformance than the D7E’spredecessor machine. Thecontinuously variable electric drivetrain also means there are no gearsto shift, so operators can concentrateon guiding the machine andcontrolling its implements.



What is electric drive?

The D7E’s electric drive system useselectrical components (generator,power inverter and the electricpropulsion module) in place of sometraditional mechanical power traincomponents (torque converter andtransmission). These electricalcomponents are designed and built tohandle the demands of track-typetractor operation. They are fully sealedoff from the environment andconnected by purpose-built,heavy-duty electrical cabling.

The D7E’s electric drive system simplyconverts engine power into electricityand then uses that electricity to powerthe drive motors and variousmachine systems. It does not storepower in a battery.

How does the electric drivesystem work?

The D7E’s electric drive power trainstarts with a proven Cat C9.3 enginewith ACERT™ Technology. The enginedrives a powerful electric generator,which efficiently turns engine powerinto AC electricity.

The electric current flows through apower inverter and into the propulsionmodule (electric drive motors). Thegenerator, inverter and propulsionmodule together form the “electricdrive train,” taking the place of thetorque converter and mechanicaltransmission of a power shiftdrive train.

The power inverter converts AC currentfrom the generator into DC current. TheDC current is used for machine controland to provide power to accessorysystems such as heating, airconditioning, ventilation, water pumpsand more. The power inverter thenconverts the current back to variable-frequency AC and routes it to thepropulsion module, which deliverssmooth, well-modulated power to thefinal drives.

Is the D7E a “hybrid” machine?

The D7E has an advanced ElectricDrive power train that is designedspecifically to meet demanding dozerapplications, while enabling significantimprovements in productivity, efficiencyand sustainability. It can be considereda hybrid in that it combines a dieselengine with an electric generator toprovide propulsion. However, unlikeautomotive hybrids, it does not use abattery or capacitor to collect, store orrelease energy during operation. TheD7E does capture mechanical energy inthe flywheel that is generated duringbraking, providing more efficientdirectional shifts and contributing tothe overall efficiency of the machine.This technology is often referred to asa diesel-electric hybrid power train.

Is electric drive safe?

Yes. Electrical safety was a veryimportant design requirement duringthe development of the D7E. Cabling,connectors and all electricalcomponents had to be engineered tosafely withstand the rigors oftrack-type tractor applications beforeCat engineers could consider usingthem in a production machine.

Electrical components have beensafely used in many types of heavyequipment for decades (even underwater, in the case of equipmentranging from submersible pumps tosubmarines). With similar precautionsused with, say, high-pressure hydraulicsystems, you can be confident in yourpeople’s ability to work safely withthe electric drive system. Consultthe machine’s Operation andMaintenance Manual for completesafety information and procedures.

Electric Drive System


> Improved steering performance

Power Inverter

Electric Cables

Generator

Engine

Final Drive

Propulsion Module

D7E Beltless Engine

Accessory Power Converter


Why does the D7E have asingle lift cylinder? Is dozingperformance affected?

The single lift cylinder on the D7Edelivers the same dozing performance,power and stability as a dual-cylindersystem. The advantage is that it usesless than half the components. Thathelps reduce lifetime operating andservice costs, especially when coupledwith the fact that the single-cylindersystem’s components are larger,stronger and more resistant to wearor damage.

For example, there are half as manyseals as in a dual-cylinder system, andthe seals are larger, thicker and betterable to reject contamination. Also, thesingle-cylinder system does not requirea quick-drop valve. Larger ports on thesingle cylinder and shorter hose lengthallow the blade to drop quickly bygravity alone.

Although dual-cylinder systems looklike they add stability, they are actuallyplumbed to act as a single unit. Theyoffer no additional resistance tounequal pressures on either side of theblade. Only the tilt cylinder mounted tothe push arm provides tilt resistance.Tilt forces on a two-cylinder lift systemcause one cylinder to extend and theother to retract as the cylinders simplyexchange fluid.

How will this tractor operate in water?

The D7E delivers equivalentperformance to the D7R Series 2 inwater. All electric drive componentsare fully sealed to keep water out andallow for safe operation in damp, wetand submerged conditions. Of course,all tractors are limited to running inwater that comes up no higher than thebottom of the engine fan, unless theyare specially equipped forhigh-water fording.

How is the stability on slopes?

Operators report that the D7E worksbetter on slopes than previous models,not only as the result of excellentbalance and a low center of gravity, butalso because the electric drive offersinfinitely variable speed for maximumtraction and control. The electric drivesystem also eliminates uncontrolledfreewheeling caused when an operatorinadvertently puts a power shifttransmission into neutral on a slope.

What kinds of technologyenhancements or information systemsdoes the D7E offer?

The D7E comes from the factory grade-control ready, which makes installationof the AccuGrade® system much faster,easier and less expensive. Product Linkis also a standard feature. This systemcan provide a range of real-timetransmittable and downloadable datathat can facilitate more effectivemachine management.



Will the power train life of the newD7E be as good as the D7R Series 2?

In most cases, it will be substantiallybetter. The D7E’s electric generator,power inverter and drive motors areexpected to last up to 50 percent longerthan today’s power shift transmission(excluding bearings and seals) withoutrequiring a rebuild. The fact that theelectric drive train has 60 percentfewer moving parts translates directlyinto high reliability and long service life.

The extended drive life changes thetotal lifetime ownership and operatingcost equation. It pushes electric drivetrain rebuild costs to much later in themachine’s operating life, which in turncan have a powerful impact on thelength of time D7E owners keep theirmachines in service.

How strong is the machine’s torque?Does the torque come on smoothly?

The new electric drive system deliversoutstanding torque in either direction,with smooth torque modulation thatmakes operation easy and predictable.The D7E’s torque is very strong,providing enough drawbar force toexceed tractive capability in almost allsituations, but with precise control thatallows operators to apply exactly thetorque needed for the operatingconditions.

Will D7E operators be able to adjusttop speeds and machine sensitivities?

Yes. Operators have the ability toset their desired top travel speedfor the specific application theyare performing.

This functional capability, combinedwith the electric drive system,enhances overall performance. Theoperator does not have to constantlychange the desired top travel speed,because the electric drive train systemoptimally and automatically adjusts itsspeed to varying loads.

How is the D7E’s electric drive systemdifferent from those found on othertypes of heavy equipment, such asmining haul trucks?

The D7E’s electric drive system isengineered specifically for track-typetractor use. It features some crucialinnovations that make it well suitedto track-type tractor forward/reversecycling operations.

All the electrical components in theD7E drive train are completely sealedoff from the environment andliquid-cooled. Robust sealing andjacket cooling enable the electric drivesystem to work easily and safely inthick dust, deep mud, heavy debris andeven in water.

Brushless motors have minimalelectrical contacts between movingparts, which cuts out potential wearand failure points and reduces serviceand maintenance requirements.Brushless technology is so superior, infact, that it is becoming the standard inall types of electric drive systems.

Do the liquid-cooled drive componentsrequire a separate radiator?

Yes and no. The generator and powerinverter are jacket-cooled, whichmeans liquid coolant circulates aroundthem in a sealed jacket. The coolantthen circulates through a separateradiator circuit built into the mainengine radiator. Although the engineand drive train coolant remain isolatedfrom each other, the radiator appearsand acts as one integrated unit. All theradiator cores are in a single plane, sothe entire radiator system is easy toclean and service. So, yes, the jacketcooling system has its own radiator, butno, it is not a completely separate unit.

Electric Drive System (continued)


> Single lift cylinder

> Operation in water

Drive Motors

Electric Generator

Power Inverter


• A rotating bushing design allows thecenter tread idlers and sprocketsegments to last through at least twosets of track.

• An open and smooth roller framedesign reduces mud buildup andenables easy clean-out.

In addition, all SystemOneundercarriage components aredesigned to work and wear as asystem. They deliver long, balancedwear life and require very little servicebetween undercarriage overhauls.

Operating the D7EWhat are the operator benefits of thenew cab design?

• Increased Visibility—The newcenter-post cab is larger overall, withlarger windows and improved viewingangles. That works with the overalldesign of the machine to providemuch better visibility all around,especially to the critical areasaround the blade.

The effect of this unprecedentedvisibility is immediately apparent whenan operator steps into the cab.Operators experience a 35 percentincrease in forward visibility becausethe precleaner, exhaust and single liftcylinder all line up with the center postcab. Rear views are also improved, inaddition to views to the sides andblade corners.

• Added Comfort—Operator comfortwas a top design priority on the D7E.The ergonomically designed steering,speed and implement controls andthe air ride seat are all fullyadjustable for maximum comfort andoperating efficiency. As a result,operators experience less fatigue andremain more productive throughouttheir shifts.

• Lower Noise Levels—Theself-contained HVAC (Heating,Ventilation, Air Conditioning) systemis mounted outside and to the rear ofthe cab. In combination with otherimprovements, this configurationhelps reduce noise levels inside thecab by 50 percent.

The D7E is quieter on the outside, too.The electric drive motors areessentially silent, and electric driveenables the engine to operate in atighter power band, so high revving isdramatically reduced. As a result,outside noise levels are dramaticallyreduced compared with the D7RSeries 2.

Cat Track-typeTractor Product LineWhat’s happening to the D7R Series 2?

The D7R Series 2 will remain availablealong with the D7E until mid 2010,before the former is eventually phasedout in regulated markets.

Why did Caterpillar start with the D7for electric drive? What’s next in themachine line?

The D7 size class offered a “just-right”sized platform for the new electricdrive system, which helped to facilitatethe E Family development process. Asmore product development occurs,electric drive may expand into otherclass sizes.

For more information on the D7E, visit www.cat.com/D7E



Why does Caterpillar use alow-drive undercarriage configurationon the new D7E?

Since Caterpillar was redeveloping thecenterline of the new machine for theelectric drive system, there was anopportunity to design a completely newtrack system that could deliver moreversatility with even lower operatingcost. That opportunity led to thedevelopment of an all-new low-drive(or oval track) configuration.

Before Caterpillar engineers chose alow-drive undercarriage design for theD7E, they very carefully weighed itsadvantages for the D7E’s intendedapplications. The mix of applications forwhich customers use D7-size machineshas changed since the introduction ofthe original Cat D7H. Customerstoday—especially those working in sitepreparation applications—demandmuch more maneuverability from thissize of machine than they didtwenty-some years ago when the firstCat D7H models were produced.

As they developed the D7E, Catengineers wanted to retain theadvantages of high drive, but also gainsome additional benefits. Their goalwas to make the D7E as productive andcost-efficient as possible in itsintended applications.

How does the new configurationcompare to the high-drive system onprevious models?

Any high-drive configuration offersthree key benefits: 1) easy serviceaccess to the transmission, 2) theability to use suspended undercarriageand 3) the mitigation of final driveshock loads. Let’s look at how the D7E’sdesign addresses each of these.

• Service Access—The D7E’s designhandles drive system serviceability ina different way, but it provides muchof the same level of accessibility as ahigh-drive configuration. For starters,there is no transmission to service.All the electric drive systemcomponents are modular, and all areaccessed under the tilt cab. The drivecomponents also need less totalmaintenance and service than themechanical systems found inprevious models. So the D7E not onlyprovides easy service access, it alsoneeds less lifetime service and thusdelivers lower total drive systemoperating costs than previousD7 models.

• Suspended Undercarriage—Theprimary purposes for a suspendedundercarriage are to improvetrack-to-ground contact in rocky anduneven applications and to improveoperator ride.

Cat D7-class tractors have alwaysdelivered long, dependable servicelife in their intended applicationswithout a suspended undercarriage.Note, however, that Caterpillar plansto keep high drive and suspendedundercarriage on D8 andlarger tractors.

• Shock Loads—To make sure the newlow-drive system could handle theimpact loads of a typical D7application, Cat engineers used D10T-capacity sprocket bearings on theD7E. They also designed theundercarriage system to direct shockloads through the roller frame,instead of directly through the finaldrives. With these enhancements andother advances in materials andengineering, it was possible to“extend” a low-drive configuration(already used on many smallerCat track-type tractors) into thelarger D7 size.

Add the enhanced visibility of theD7E’s low-drive system (especially tothe sides), and it becomes clear thatthis is the best design for the newmodel—one that will deliver thelowest possible operating costs andmaximum operating efficiency in amuch wider range of applicationsthan ever before possible with aD7-class machine.

Will SystemOne™ be available onthe D7E?

A heavy-duty undercarriageconfiguration will be standard on theD7E, and SystemOne will be availableas an attachment option.

SystemOne undercarriage has beenproven to reduce total undercarriagecosts by 35 percent to 70 percent.These cost savings come fromspecialized components that reducewear, offer longer life and dramaticallycut total lifetime maintenance needs.

• Lifetime sealed and lubricatedcartridge eliminates bushing turns.

• Sprockets require no replacementduring the life of the chain.

Undercarriage


> D7E undercarriage

> Cab visibility

> HVAC system

d7e faqs

Documents