Loy Yang Power drives long-term success An innovative drive solution – founded on Rockwell Automation’s PowerFlex 7000 mediumvoltage drive – helps streamline Loy Yang Power’s mine conveyor system upgrade.

SolutionsThe introduction of an innovative drive solutionincluded:

• 4 Allen-Bradley PowerFlex 7000 mediumvoltage (MV) AC drives

• 4 stainless steel cooled and removable driveenclosures

• 4 Allen-Bradley electronic operator interfaces

ResultsThe Rockwell Automation PowerFlex 7000 drivesolution delivers:

• Minimised production stoppages, breakdownsand unscheduled downtime

• Advanced diagnostics and troubleshootingcapabilities

• Reduction in maintenance

• Easy integration with existing drive systems andcontrol architecture

• Elimination of isolation transformers

• Space-efficient speed and torque control

• Minimal component count

• 24/7 operation

The Rockwell Automation air-conditionedremovable drive enclosure delivers:

• Operational flexibility (Each cooled drivepackage can be installed/uninstalled on any ofthe mine’s conveyors.)

• Protection of drive electronics from extremelydusty conditions experienced in the mine.

• Elimination of water-cooled drive system andimproved drive cooling reliability

• EOI access to drive diagnostics

In Australia, coal-fired power generation has established itself as avaluable power source, providing vast quantities of inexpensive andreliable electricity. It accounts for approximately 75 per cent of thecountry’s annual electricity production. Keeping Australia’s coal-firedpower generation infrastructure online – from the coal mine through tothe generating plant and distribution grid – goes some way to ensuringthe nation’s industrial wheels remain turning. As in all productionprocesses, stoppages, breakdowns and unscheduled downtime can becrippling to the power generating process. Such outages can have adevastating effect, impacting both the energy producer’s and end-users’bottom lines in a matter of minutes.

One energy industry stakeholder leading the way in providing industry withan uninterrupted supply of electricity is Victoria's largest energy producer,Loy Yang Power. Located within the heart of the Latrobe Valley, 165kilometres east of Melbourne, Loy Yang Power provides reliable and efficientenergy for industry and consumers right across south-eastern Australia.

As part of the company’s ongoing commitment to producing reliable cost-efficient energy, Loy Yang Power recently embarked on an upgrade of itsfour-level open-cut coal mine facility, Loy Yang Mine. The ‘in progress’upgrade includes the redesign and progressive changeover of the mine’sexisting coal transfer conveyor drive systems. To obtain a drive solution

In a collaborative effort, Rockwell Automation and the Loy Yang Power engineering team developed a new drive solution,founded on the Allen-Bradley PowerFlex 7000 medium voltage (MV) AC drive.

capable of withstanding the ruggedmine environment while deliveringpremium around-the-clockperformance, Loy Yang Powerenlisted the engineering experienceof Rockwell Automation®.

Coal to kilowattsWith an annual output ofapproximately 30 million tonnes ofbrown coal and four million cubicmetres of overburden (soil thatoverlays the coal seams), Loy YangMine is the largest coal-producingmine in the southern hemisphere.The mining process and thetransportation of the coal from thebottom of the mine to the power

stations is largely automated andfeatures a range of sophisticatedmining and materials handlingtechnologies.

Huge electric-powered bucket-wheeldredgers, 50 metres high and 190metres long, patrol the open-cutmine ‘benches’, each excavating up to4,000 tonnes of coal per hour onaverage. The bucket wheel of eachdredger feeds on-board dredgerconveyors, which in turn deposit thecoal onto main transfer conveyor

systems on each level of the mine.Each transfer conveyor systemcomprises multiple separateconveyors, each with a belt-width oftwo metres and a travel speed of 5.2metres/second (19 km/h). With acombined length in excess of 25kms,the mine’s conveying systemtransfers the freshly mined coal fromthe mine floor to the surface.

The transfer conveyor systemstransfer the coal to a raw coal bunker,which has a 70,000-tonne capacity.The coal is then transported directlyfrom the bunker (also by conveyor) totwo separate power stations locatedat the ‘mouth’ of the mine. These areLoy Yang Power's 2,100MW power

station and International Power's LoyYang B 1,000MW power station.

Continuous conveyingAccording to Loy Yang Mine seniorelectrical engineer, Steve Cleaver,providing a steady flow of coalfeedstock to the coal bunker isessential to keeping the powergeneration process online andproducing cost-effective electricity.“The coal bunker only has enoughcapacity to fuel twenty hours of

power generation. Therefore, thepressure on the conveying system toperform is relentless,” he says.

The legacy transfer conveyor drivesystems at Loy Yang Mine were basedon water-cooled eddy-currentcoupling (ECC) technology. Whenfirst installed many years ago, theECCs were the ideal drive solution forproviding high torque over a widespeed range – perfect for haulingenormous quantities of coal from thebottom of the mine to the surface.

However, in recent years, it hadbecome clear to the Loy Yang Powermine engineering team that the legacydrive systems were struggling to movethe coal as efficiently as they believedwas now possible. Furthermore, theexisting drive cooling systems were notcoping with the production demandand were frequently overheating. “Wecan’t afford to have a conveyor go off-line, especially given the ever-increasing demand for electricityduring peak-load periods,” Cleaver says.“When we’re off-line we’re not sellingelectricity, so downtime is catastrophic.It was time to make a change.”

Maintenance headachesAccording to Cleaver, the ongoingmaintenance and performance of theECC drive cooling systemscomplicated matters. “The water tendsto corrode the metal on the movingparts and contributes to an increasedair gap between rotor and drum, anddrum and stator. This increased air gapreduces the machine efficiency,” saysCleaver. “In addition to this, thecooling systems were increasinglyunable to cope during periods of peakdemand in the summer months. Weneeded to upgrade.”

The mine upgrade provided Loy YangPower with the opportunity toimplement a drive solutionincorporating the latest technology.“Our legacy drive system had servedus well over the years, but it was timefor a more reliable system withadvanced capabilities,” he says. “Withso many conveyors on-site, it wasimportant that the new drive

Loy Yang Mine senior electrical engineer, Steve Cleaver (left), and Rockwell Automation technical consultant, Gary Spotswood,inspect the inside of one of the portable drive packages.

technology could be brought onlinegradually and was able to integratewith our existing drive systems andcontrol architecture,” says Cleaver.

Compact, contained andcooledIn a collaborative effort, RockwellAutomation and the Loy Yang Powerengineering team developed a newdrive solution, founded on the Allen-Bradley® PowerFlex® 7000 mediumvoltage (MV) AC drive. Featuring‘Direct-to-Drive’ technology – atechnology that helps eliminate theneed for isolation transformers onapplications with either new orexisting motors – the Allen-BradleyPowerFlex 7000 MV AC driveprovides space-efficient speed andtorque control across a range ofdemanding drive applications.

The mine engineering team came upwith an idea to equip each conveyorwith a fully self-contained, cooled andremovable drive package that couldbe easily installed or uninstalled on

any of the mine’s conveyors. “Thislevel of portability provides us withimproved production flexibility,”Cleaver says. “It allows us to physicallylocate the drive package at any of theconveyors on any level of the mine, asconveyor length or lift requirementsdictate.”

Cleaver also stipulated that the drivepackages be housed in an IP67stainless steel enclosure equippedwith a closed-loop air-conditioningcooling system. “We wanted toprotect the drive electronics from theextremely dusty conditionsexperienced down in the mine,” saysCleaver. “It was also imperative thatthe drive packages be equipped witha reliable cooling system to avoid thecostly shutdowns we had experiencedwith the water-cooled ECC systems.”

According to Rockwell Automationtechnical consultant, GarySpotswood, the compact nature ofthe PowerFlex 7000 drive simplifiedthe development of the portabledrive packages. “The transformerless

configuration of the PowerFlex 7000meant we were able to help minimisethe footprint of the drive package,”he says. “We developed a partitionedstainless steel IP67-rated enclosure,equipped with an air-conditionedcooling system, to house each of the6.6kV PowerFlex drives. Not only wasit a more elegant drive set-up, it alsoeliminated the mixture of water andelectricity used with the ECC coolingsystems.”

The ‘minimal component count’ wasalso a feature of the PowerFlex drivesolution. “Fewer parts means thatthere are fewer things to go wrongand fewer spares to keep on-site,”says Cleaver. “Most componentchange-overs take less than 30minutes – a real time saver.”

Seamless integrationFour drive packages have beeninstalled on the Loy Yang Mine siteto-date – two on the lower level andone each on the middle and upperlevels. One of the challenges here

Bucket-wheel dredgers feed on-board dredger conveyors, which in turn deposit the coal onto main transfer conveyor systems on each level of the mine.

was integrating the new RockwellAutomation drive technology withthe mine’s existing drive technologyand control architecture.

Each of the PowerFlex 7000 drivepackages is interfaced with aprogrammable logic controller (PLC)located in the neighbouringswitchroom. Each PLC is, in turn, linkedto the mine’s supervisory control anddata acquisition (SCADA) system, viathe mine’s existing communicationsnetwork. Each drive package isequipped with an Allen-Bradleyelectronic operator interface (EOI)located on the front panel of the driveenclosure. “The drives can beinterrogated via these EOIs or throughthe mine’s SCADA system,” saysSpotswood. “The locally mounted EOIsmake it easier for site personnel toaccess drive diagnostics withoutopening the dust-proof enclosures andexposing the drives to the elements.”

The Rockwell Automation/Loy Yangengineering team developed astrategy that allowed the new drivepackages to seamlessly synchronisewith the existing ECC drives. “Allconveyors have been set up to run insequence. Where appropriate, thedrives have been configured tooperate in a ‘master/slave’configuration,” says Cleaver. “We setup one master drive to control thespeed, while the other drives become‘torque followers’. With the conveyorspeeds perfectly matched, thetransfer of coal from one conveyor toanother is seamless.”

Explain and trainAccording to Cleaver, RockwellAutomation’s support from theproject’s inception and design

phase, through to the first phase ofsupply and installation was second-to-none. “The mining operation isessentially a 24-hour operation,” hesays. “It was reassuring to knowRockwell Automation support wasavailable 24/7. There were manyconversations in the middle of thenight and early morning.”

Cleaver was especially impressedwith Rockwell Automation’swillingness to fully explain the innerworkings of its drive solution. “Wedidn’t want any proprietary ‘blackbox’ technology,” says Cleaver. “In aprocess such as ours, we can’t affordto wait around for specialised serviceteams. We need to be familiar withthe product and its inner workings sowe can set it up, monitor it andtroubleshoot it if necessary. RockwellAutomation was excellent in thisrespect; they were able to ‘explainand train’.”

With the mine upgrade at Loy YangMine only partially complete, thereis much work ahead. Cleaver and histeam are planning to progressivelyreplace many other ECC drivesacross the mine with PowerFlex7000 drives. “We have beenimpressed with the RockwellAutomation drive solution,” saysCleaver. “It provides us with thecombination of reliability andperformance we are looking for.”

Loy Yang Mine also has plans toimplement a downhill conveyingsystem to begin filling in certainportions of the mine. “The active frontend (AFE) rectifier and regenerativebraking capabilities of the PowerFlex7000 drive will be incredibly valuablehere,” says Cleaver. “As the overburdenis backfilled downhill into the mine,electricity will be generated and fedback into the grid. It’s smart solutionslike this that make our job easier.”

Publication DRIVES-AP004A-EN-P – December 2008 Copyright ©2008 Rockwell Automation, Inc. All Rights Reserved. Printed in Australia.

Conveyor L210 is equipped with a fully self-contained, cooled and removable drive package that can be easily installed oruninstalled on any of the mine’s conveyors.

Rockwell Automation, Allen-Bradley, PowerFlex are trademarks or registered trademarks of Rockwell Automation, Inc. Trademarks not belonging to Rockwell Automation are the property of their respective owners.