In This Issue

Vol. 2, No. 4 EPRI Power Electronics Applications Center December 1995

◗ ASD research gets a big “brake” on the road to system compatibility.◗ Thanks to a new consensus, the line between acceptable and unaccept-

able voltage tolerance gets nudged to benefit utility customers.◗ Weeding confusion from the field of power quality, a new publication plows

close to the corn.

See ASDs, page 3

The response of an adjustable-speed drive to voltage sagsdepends not only on the magnitude and duration of the sagbut also on the type of industrial process the ASD is control-ling. It might ride through the sag; it might trip and shutdown the process.

The effects of even a routine power disruption along thelocal grid is therefore of crucial importance to the industrialcustomers of an electric utility company. To better under-stand the effects of voltage sags on industrial processes,PEAC is expanding its ASD research to test the voltage ride-through characteristics of ASDs in different process settings.To carry out the mission of Task 26, PEAC is relying uponsupport from sponsors of the first ASD research task(Task 1) to help develop a type of load simulator called aprogrammable dynamometer, something that would enable

Researchers brake for ASDs

D. Steve RectorEPRI, Knoxville

D. Rector’s View

In August of 1986—nearly ten years ago—theElectric Power Research Institute created PEAC toconduct power quality research on behalf of sponsoringutilities. Who would have known then how consequen-tial the discipline of power quality would be to thesuccess of the electric utility industry?

Ten years ago, it was rare for a utility to have a powerquality program. Today, it is commonplace. Ten yearsago, the line between acceptable and unacceptablepower quality was virtually unknown. Today, utilities areteaming with standards groups in an attempt to under-stand and clarify these boundaries. When I think abouthow the utility industry has resolved time after time tobetter itself, a little Latin comes to mind: perspicacity.

Perspicacity, acute insight and discernment, enabledthe utility industry to transform the commotion of fingerpointing into a coordinated effort to understand, solve,and even prevent power quality problems. And theSystem Compatibility Research Project has given ourindustry the means to do so.

This issue of the System Compatibility ResearchNews celebrates PEAC’s burgeoning enterprise to helputilities understand, mitigate (in the short-run), andultimately to eliminate system incompatibilities. Wehave expanded the newsletter from two to four pages toreport the effusion of research news from our labora-tory, a further sign of the rapidly expanding importanceof power quality.

To get involved, just drop me a line at 423-974-8307or email srector@msm.epri.com.

System Compatibility

Arshad Mansoor demonstrates the effect of a voltage sag onthe speed, torque, and current of an ASD-driven motor.

Motor Speed

Current

Torque

PROJECTRESEARCH

Electric Power Research Institute • Power Electronics Applications Center

System Compatibility

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BallastInterference•

2 System Compatibility Research News December 1995

high-voltage disturbances. After theseissues are settled, a new industrystandard will emerge. The significanceto the average person isn’t lost on Dorr.“Most common disturbances that showup in our power quality surveys arewithin the boundaries of the proposedCBEMA curve. This means morepower quality-compatible equipmentdesigned to the new curve, fewerunhappy customers making calls tomanufacturers, and fewer manufactur-ers complaining to utility companies.Everybody wins.”

Contact Doug Dorr at 423–974–8348,fax 423–974–8289, emailddorr@msm.epri.com.

PEAC throws new CBEMACurve to computer industry

The System Compatibility ResearchProject is leading to big changes inmanufacturing standards for equipmentlike personal computers, cash registers,and fax machines. During the Septem-ber 1995 meeting of a working groupof the Information Technology IndustryCouncil (ITIC), PEAC LaboratoryManager Doug Dorr presented a reporton PEAC’s research into the toleranceof business equipment to electricaldisturbances and data on the electricalenvironment in which business equip-ment operate.

Dorr—who manages Task 19, aproject designed to create new marketsfor system-compatible products—lobbied successfully at the Milwaukeemeeting to get the committee to adoptseveral PEAC recommendations forchanges in the voltage-toleranceenvelope of information technologyequipment, known as the CBEMACurve. (CBEMA stands for Computerand Business Equipment Manufactur-ers Association, ITIC’s previousname.)

The CBEMA curve shows the rangeof tolerance to electrical disturbancesfor a particular type of equipment.“The standing curve is definitelyobsolete,” Dorr said of the CBEMAcurve, which, over the years, has beenadopted by manufacturers as a defaultindustry standard. “It doesn’t reflectthe performance of equipment any-more.”

Revision of the widely referencedCBEMA curve has been a major topicfor the past five meetings of the ITICworking group, designated ESC-3. “Anew curve will be ready for a vote atthe next meeting, which is in Orlandoin February (1996),” Dorr said. “Per-sonal computer designs meet this newcurve. But ITIC wants to proceedcautiously so that all other types ofinformation technology equipmentmeet it as well before they agree to it.

“The CBEMA curve was originallyintended just to be a good indicator ofwhat typical mainframe computers inthe early ’70s could actually tolerate,power quality-wise. Since that time, thecurve has taken on a significance farbeyond what was intended, and it’sbeing used as a specification for what

equipment should stand. It was neverintended for that and that’s why itneeds to be updated.”

Still unresolved is the question aboutmoving the zero-voltage ride-throughtolerance out to 20 milliseconds. Somemanufacturers said during past meet-ings that they wanted to test some fileservers and mainframes to be sure theycan ride through a 20-millisecondvoltage interruption. Before agreeingon 110 percent of nominal for eventslasting longer than one-half second, themanufacturers want more testing for

Voltage-ToleranceEnvelope

1 µs

0.5 c

3 ms 20 ms 0.5 s 2 s 10 s SteadyState

0.001 c 0.01 c 0.1 c 1 c 10 c 100 c 1000 c

Duration of Disturbance in Cycles (c) and Seconds (s)

Per

cent

of N

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500

400

300

200

100

0

Legend

Old Voltage-Tolerance Boundary

New Voltage-Tolerance Boundary

Enhanced Voltage Tolerance

Limit To Be Decided

Approved Boundary Points

Boundary Points Under Review

The area of voltage tolerance expands for computers and other office equipment astest results demonstrate that most computer equipment exceeds the originalCBEMA curve created in 1978.

System Compatibility Research News December 1995 3

ASDs, from page 1researchers to determine how wellASDs in various process conditionsride through power disruptions.

As with Task 1, PEAC engineer Dr.Arshad Mansoor is in charge of Task26. “The ASD controls the speed of themotor,” Mansoor said, explaining thecomplexity of a process environment.“Before applying the ASD, you need toknow the process it’s running. Is it apump application? A fan? Is it forplastic extrusion? Is it running a textileoperation?” Engineers and mathemati-cians use what is called a torque/speedcurve to characterize different loads,Mansoor explained, adding thatprocesses are some combination ofconstant torque and horsepower orvariable torque and horsepower.

Differences between drives also haveto be considered. “We aren’t testingmotors. We are evaluating how ASDsmaintain the process—and how longthey can maintain a process—under

See PUBLICATION, page 4

However, according to Mansoor,there many types of processes in thereal world. “As for the five-horsepowertest setups used in previous testing,they tested ASDs for only one type ofload—a motor with an eddy-currentbrake,” Mansoor said. The Task 26 testsetup calls for something much moreadaptable and sophisticated. With helpfrom sponsors, PEAC’s engineers willbuild a programmable dynamometerthat can expand the voltage-sagresearch begun on 17 types of ASDs inTask 1. It will enable researchers toprogram loads to simulate an array ofprocesses for constant torque/constanthorsepower and variable torque/variable horsepower. The data col-lected will then inform torque/speedcurves that will enable utilities to helptheir customers choose the right drivefor a particular application.

The innovative use of an old automo-tive brake system allowed investigatorsto simulate a friction- or constant-torque load on one of the original testsetups. As Mansoor explained it, “thedisc brake showed us the performanceof an ASD during and after a sag event,depending on a friction load, which isdifferent from the eddy-current brake.”With the disc-brake setup, the motorstops cold when the ASD driving ittrips because the motor load has noinertia.

The unique application of automobiledisc brakes was engineered by RonLambert. The disc brake caliper, froma 1978 Chevrolet Chevette, wasmounted on the friction load setup. Thecalipers and pads were connected to a1976 Ford Mustang master cylindercontrolled by a brake pedal from a1932 Ford. “Yes, a ’32 Ford,” Lambertsaid, “because I had it and it would dothe job.”

As for expanding PEAC’s ASD re-search, Mansoor noted that a program-mable dynamometer “is not somethingyou buy off the shelf at Radio Shack.You have to build it, which will bringits own challenges.”

Contact Arshad Mansoor at 423–974–8378, fax 423–974–8289, emailamansoor@msm.epri.com.

The inaugural issue of PEAC’snewest serial publication, PQTNApplication, the third in a series ofPower Quality Testing Network(PQTN) publications, is hot off thepress. The new document series isdesigned to help electric utility custom-ers solve and prevent power qualityproblems through the most effectiveapplications of modern technologies.

The idea for PQTN Applicationsgrew out of increasing concerns in theutility industry over its customers’need for “how-to” information. EachPQTN Application provides valuabletechnical information to end users, butthe level of technical detail varies bysubject. The language is tailored toutility customers to ensure comprehen-sion. “Utility end users want someoneto talk to about their power qualityproblems,” said Brad Connatser,PEAC’s technical writer. “Applicationsoffer an efficient compromise: Theyenable a utility representative to leavebehind a reassuring voice after theinitial meeting or telephone call.”

Connatser is ardent about the impor-tance of clearly communicating toutility customers. “Applications don’ttalk around complex subjects and theydon’t talk down to end users, but theydo talk with the authority of our powerquality experts, who do an incrediblejob researching solutions to powerquality problems.”

Regardless of the present hype aboutthe information superhighway, “peopleare not so addicted to information thatthey will plow through a lot of techno-babble to find the information theyneed to solve a problem,” Connatsersaid. The new serial publication useswhat Connatser calls “the workingvocabulary of the end user” that is sovital for how-to documents. “AnApplication can therefore guide the enduser from complication to resolution,or at least to someone who can help theend user resolve a particular problem.”

The information in PQTN Applica-tions comes directly from the results ofthe numerous tasks of the SystemCompatibility Research Project, as wellas case studies from PEAC’s PowerQuality Hotline, other PQTN laborato-

Bridging the GapA new publication brings endusers, solutions together

voltage-sag conditions before they dropout,” Mansoor said.

What is needed now is to see how thetype of process, whether a constant-torque or friction-load process, affectsASD tolerance to voltage sags. “Howdoes the response vary?” Mansoorasked. “Maybe for a pump type ofprocess, the ASD can withstand a ten-cycle, 50 percent sag. Maybe foranother, it can handle only two-cycle or20 percent voltage sag. So, when we’redrawing the voltage-tolerance envelopeto show how much disruption theequipment can tolerate, the ASD wouldbe characterized according to the typeof process it was controlling.”

Using parts from various Ford andChevrolet automobiles, PEAC’s RonLambert fabricated a friction brake toload an induction motor during ASDtesting.

Sponsored by EPRI and itsmember utilities, the SystemCompatibility Research Project is aprogressive research effort toimprove compatibility between thepower system and end-use equip-ment and appliances. By sponsor-ing a task of the project, utilitieschoose which equipment andappliances will be characterized.Utilities can finance their sponsor-ships through either a TailoredCollaboration Agreement orCofunding Agreement with EPRI.All testing is conducted at PEAC’sPower Quality Test Facility or atother test facilities within the PowerQuality Testing Network.

For more information aboutsponsoring a research task, contactSteve Rector, EPRI-Knoxville, orGene Sitzlar, SC Research ProjectCoordinator, at 423-974-8288 orfax 423-974-8289.

EditorGene Sitzlar

Managing EditorBrad Connatser

4 System Compatibility Research News December 1995

Printed with soy inks on recycled paper (at least 50% recycled fiber, includingat least 10% postconsumer waste) in the United States of America.

Tom KeyPEAC

System CompatibilityHighlights

PUBLICATION, from page 3ries, and field investigations. “Thisdiverse information is channeled andtranslated into how-to publications thathelp utility end users bridge the gapbetween theory andapplication,” Connatsersaid, explaining how thedocument got its name.

PEAC started work-ing with utilities in 1994to develop an applica-tion guide that could becustomized on requestby a qualifying utility,even to the extent ofchanging the logo andcolor scheme to matchthe utility’s literature.“This allows PEAC tobe an invisible butsignificant part of autility’s problem-solving efforts,”Connatser said. “It alsoenables the utility tostrengthen its customer relationships bydemonstrating to customers that theutility cares about their power qualityproblems.”

Each PQTN Application focuses on asingle topic. The first five issues tacklethe following subjects:

■ Mitigating the Effects of Line-Current Unbalance on Adjustable-Speed Drives

■ Avoiding Temporary Blackouts ofHigh-Pressure Sodium Lamps

■ Avoiding Temporary Blackouts ofMetal Halide Lamps

PEAC’s technical writer Brad Connatser interrupts hisproofing of the first five PQTN Applications to inspect theprinting plate of PQTN Application Number 1.

■ Eliminating the Jitters in ComputerMonitors

■ Sizing Single-Phase Uninterrupt-ible Power Supplies

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For more information about custom-izing a batch of PQTN Applications,contact Brad Connatser, technicalwriter, at (423) 974-8316;fax: (423) 974-8289.

This year, your system compat-ibility research program has madegreat progress. With individualutility support, we have investi-gated personal computers, lightflicker, lighting interference, PLCs,and ASDs, among others. Task 8,the most flexible part of theprogram, allowed sponsoringutilities to look at HID lighting,lamp dimmers, ballast failures, andcomputer-generated harmonicloading of building wiring. The bestnews of all is that the program hasbrought together utilities andmanufacturers with an unprec-edented spirit of cooperation. Todate, we have signed over 100agreements with manufacturers toimprove the compatibility of morethan 200 different products.Standards groups are also partici-pating in the program. TheCBEMA article (page 2) illustrateshow the results of our program areinfluencing computer tolerancedesign goals. At the NEMA ballastmanufacturers meeting on theASNI C62 standard, we proposeda limit and measurement methodfor flicker-free lighting. At the lastmeeting of the NEMA ASD manu-facturers, your results lead to amotion to develop a ride-throughtolerance envelope for ASDs.

Are these efforts on target andmeeting your power qualityneeds? Please send your com-ments to keytopq@aol.com or call423-974-8336.

EPRI Power Electronics Applications Center10521 Research Drive, Suite 400Knoxville, Tennessee 37932

NL-106020

© 1995 Electric Power Research Institute, Inc.

Electric Power Research Institute and EPRI are registered service marks of the Electric Power Research Institute, Inc.