The What's Inside Product Safety

Product Safety Newsletter •

TheProductSafetyNewsletter

®

Volume 4, Number 2 March/April 1991

Continued on page 16

Guest Editorialformer or subscribing to the latter -why wait any longer?

A Few ChangesThe most dramatic change is thatRich Pescatore is stepping down asChairman. Committee officers gen-erally have a two year term of officein the EMC Society. By the timeyou read this, votes should be in forthe new officers, but since it is notyet official I will only mention thatI hope to be back as Secretary /Treasurer. (On the other hand, ifsome helpful volunteer should hap-pen to be able to take over as Trea-surer, splitting the position wouldcertainly make my life easier!)

Seriously, participating in a organi-zation such as this is a very reward-ing experience, both personally andprofessionally. If product safety ispart of your job, then time spenthere is time well spent. You canlearn from your peers, make valu-able contacts, increase your profes-sional recognition, influence thefuture of product safety standards

and processes, and even have fun.Does this sound a little like a salespitch? Well, it is one! If you wouldlike to hear the rest of my spiel, feelfree to call me at 408-447-0738.

The Product Safety Newsletter isreally steaming along now that KenWarwick has taken over the layoutand production role. An issue everyfive or six weeks at first has caughtus up to our regular schedule. Con-tributors are very welcome - ar-ticles, news items, letters and more- we are glad to be able to provide aforum for product safety. Contri-butions also are very welcome - ifyour company could benefit froman Institutional Listing and wouldlike to support the publication ofthe Product Safety Newsletter,please let us know.

One important note: if you don’twant to miss your issue of the Prod-uct Safety Newsletter soon, you’dbetter REMEMBER TO SEND IN YOUR

SUBSCRIPTION RENEWAL NOTICE.

Product Safety Technical Com-mittee (TC-8) ReportDoes it sometimes amaze you howfast time goes by? More than twoyears have passed since the forma-tion of TC-8 and more than threeyears since the first publication ofthe Product Safety Newsletter. Ifyou have been “meaning to getaround to” inquiring about the

Guest Editorial ............................................................ 1

Officers of the PSTC's ................................................ 2

Laser Requirements Harmonization Meeting ............. 3

Letters to the Editor .................................................... 4

Hazard Markings: Signal Word and

Color Perceptions .................................................. 5

News and Notes ......................................................... 6

Revised Swediish Standard for Testing

Visual Display Units ............................................... 7

NRTL Marking Requirement ....................................... 9

NEMKO's TBM Program .......................................... 10

IEC 950 Questions and Answers ............................. 11

Power Factor Correction for European Use ............. 12

Institutional Listings .................................................. 20

Area Activity Reports ................................................ 21

Area Activities Calendar ........................................... 22

Subscription Renewal Form ..................................... 23

What's Inside


Central PSTC (TC-8)Chairman Richard Pescatore (408) 447 6607Vice-Chairman (vacant)Secretary-Treasurer John McBain (408) 447 0738

(408) 257 5034 (fax)Standards Chair Tania Grant (408) 942 2569Paper Review Mike Harris (707) 258 1360Symposium Chair (vacant)

Central TexasChairman Pro Tem Vic Baldwin (512) 469 7289

(512) 469 7350 (fax)

ChicagoChairman Dick Hagedorn (708) 505 5722Vice-Chairman John Allen (708) 827 7520

Orange County/Southern California Chairman Charlie Bayhi (714) 730 2556Vice-Chair

/Program Chair Ercell Bryant (714) 966 3459Secretary/Treasurer Paul Herrick (714) 770 1223

PortlandChairman Fran Pelinka (503) 641 4141Secretary-Treasurer Art Henderson (503) 777 8111

San DiegoChairman Scott Bonnet (619) 592 4571Co-Chairman Dave MacKenzie (619) 793 0858Vice Chairman Ray Jimenez (619) 726 9303Co-Secretary Gene Biggs (619) 592 8236Co-Secretary Tom Arno (619) 755 5525Treasurer Tom Barker (619) 592 8104Program Co-Chair Tom Radley (619) 592 8104Program Co-Chair Dave MacKenzie (619) 793 0858Program Co-Chair Frank Henzel (619) 578 7999

Santa Clara ValleyChairman John Reynolds (415) 335 1344Vice-Chairman

/Program Chair Mike Campi (408) 954 1800Treasurer Mark Montrose (408) 524 8129Secretary David McChesney (408) 985 2400 X2771

SeattleChairman Walt Hart (206) 356 5177Membership Chair Heber Farnsworth (206) 356 6045


The Product Safety Newsletter ispublished bimonthly by the Prod-uct Safety Technical Committeeof the IEEE EMC Society. Nopart of this newsletter may bereproduced without written per-mission of the authors. All rightsto the articles remain with theauthors.

Opinions expressed in this news-letter are those of the authorsand do not necessarily representthe opinions of the TechnicalCommittee or its members. In-deed, there may be and often aresubstantial disagreements withsome of the opinions expressedby the authors.

Subscriptions are free. To re-ceive a subscription, send yourrequest to:PSN Subscriptions,John McBain (m/s 42LS)c/o Hewlett Packard Co.19447 Pruneridge AvenueCupertino, CA 95014Fax No. (408) 257 5034

Comments and questions aboutthe newsletter may be addressedto:The Product Safety Newsletter,Roger Volgstadt (Loc. 55-53)c/o Tandem Computers10300 North Tantau AvenueCupertino, CA 95014Fax No. (408) 285 2553

Editor: Roger VolgstadtNews Editor: David EdmundsAbstracts Editor: Dave LorussoPage Layout: Ken Warwick

Subscriptions: John McBain

Circulation: 950

Officers of the ProductSafety Technical Committees


1. Revise the time basis for classifi-cation for those laser products whichemit laser radiation at wavelengthsgreater than 400 nm which are notintended to be viewed. This appliesonly to the use of Class 1AEL’s.JUSTIFICATION: Harmonizationwith IEC TC76/WG1 proposal forrevision of paragraph 9.3ii, and torecognize realistic exposure condi-tions.

2. Consider the extension of Class 2into the infrared based upon theconcept of behavioral limitationsupon exposure duration.JUSTIFICATION: To address theconcerns of IEC TC76/WG5 andthe proposal of WG1 to reduce theabrupt transition from Class 1 toClass 3A and Class 3B in theinfrared.

3. Revise the measurement criteriafor other than collimated beams tomeasure with a 3.5 mm aperturelocated at a distance of 10 cm fromthe apparent source with 10 dioptercollimating optics or less. A 7 mmaperture would be used for colli-mated beams for products intendedto be used in a locale where theemitted laser radiation is unlikely toviewed with optical instruments. A50 mm aperture would be used withthe same collimating optics wherethe laser product can be expected tobe viewed by opticalaids.JUSTIFICATION: To harmonizewith an expected change in IEC 825and to recognize the possibility ofstrong myopes being able to view at10 cm with a sharp retinal image.

Laser RequirementsHarmonization Meeting

by Brady TurnerHewlett PackardGreeley, Colorado

On January 28 and 29, 1991, repre-sentatives from the Center for De-vices and Radiological Health(CDRH), the US Army, IEC TC76,and industry met to discuss harmo-nization between the United Stateslaser product requirements (21 CFR1040) and the international laserproduct requirements (IEC 825).

There are several factors motivat-ing this effort:

a. The need for harmonizationof all US standards withinternational standards,specifically the laser safetystandard of the InternationalElectrotechnical Commision(IEC), IEC 825.

b. The need to adjust AccesibleEmission Limits (AEL’s)and measurement criteria inthe Federal standard inaccordance with new bio-logical data.

c. To resolve problems relatedto new applications of lasertechnology.

Over the course of the two days,eighteen changes to the two stan-dards were drafted. These propos-als will be submitted to the CDRHand the IEC through TC76. Ifadopted, these proposals would vir-tually eliminate all variations be-tween the two standards.

Recommended Changes to Both21 CFR 1040 and IEC 825

4. Propose the wording on protec-tive housing labels with simplified,more generic, such as “CAUTION,Laser Radiation Inside, Avoid Ex-posure.” The ISO/IEC effort torevise safety symbols needs to beclosely watched to maximize har-monization.JUSTIFICATION: To facilitatecompliance.

5. Eliminate the requirement foremission indicator on lasers emit-ting Class 3A levels or less and toadopt the current recommendationof IEC/TC76 to place emissionindicators on remote exit apertures.JUSTIFICATION: Harmonizationbetween 21 CFR and IEC 825

6. Revise the AEL for Class 1 at1535-1545 nm to apply to all expo-sures less than 10 seconds in thespectral region 1530 to 1550 nm.JUSTIFICATION: To more realis-tically fit biological data.

Recommended Changes to 21CFR 10407. Revise Class 1 AEL’s for wave-lengths between 550 nm and 1400nm for emission durations greaterthan or equal to 10 seconds. It isproposed that the AEL’s be thesame as those in ANSI Z136.1 andIEC 825 as amended.JUSTIFICATION: For harmoniza-tion with IEC and to more closelyfit actual biological data for retinalinjury.

8. Extend the CDRH definition forContinued on page 15


Letters to the Editor

Best regards,Don Clayton

[Have any readers had experiencein using this type of circuit in theirproduct certifications? When is ithelpful to use “limited current”rather than “SELV” (or other) inproduct descriptions? Please sendyour comments and recommenda-tions to the Editor. - Ed.]

“Sweden Sour”:

My thanks to you, and especially toRich Pescatore, for a really fine jobin bringing about the Product SafetyNewsletter.

As you might guess from my com-ments on future articles in the News-letter, I have a strong interest inEuropean safety laws. This cameabout after I discovered that theSwedish safety testing group,SEMKO, does not recognize TÜV.This, indeed, was a painful andcostly discovery, and one whichcaused us to scramble quite a bit.

By the way, what do other folks dowith respect to shipping productinto Sweden? Do they use a “na-tional” testing agency (e.g. - BSI,VDE) or are they able to use TÜV?

My last comment concerns theNortheast Product Safety Group.The piece about it was quite good,although it didn’t accurately por-tray all of the politics involved. The

Limited Current Info Needed:

Dear Sir:

I would appreciate your help inbetter understanding the actual in-tent of Sub-Clause 2.4.1 of IEC 950regarding limited current circuits.Where are limited current circuitsrequired? This Sub-Clause makesno mention of voltage levels. Is it tobe implied that limited current cir-cuits are also at hazardous voltagelevels? One example I can give isthe personal computer interface cir-cuits which are operator accessible.Obviously I/O circuits with +5VDCsteady-state output can put 2.5 mathrough the 2 kohm test resistor.

Perhaps this Sub-Clause applies towet-use applications or medical in-stallations? I hope you or one ofyour associates can shed some lighton this requirement.

Because the town of Grass Valley isso far from Santa Clara Valley, Ihave not been able to attend theregional meetings.

ProductCompliance,

First Principles

EMC & SafetyColloquium

Santa Clara ValleyCalifornia

June 12-13, 1991

for information,please call

(408) 922-4444X9346

outcome, not to be associated withthe IEEE, disappointed many of themembers.

Thanks again.

Jerry KutcherXerox Imaging Systems, Inc.Director Quality

[Are any readers able to answerthese questions? Please drop us aline. - Ed.] ❖


ward these commonly recognizedprinciples in hazard markings.

We believe that our data shows thatthere is usually enough differentia-tion between the signal words orcolors to proceed with the introduc-tion of the ANSI standard Z535.4.The proposed ANSI Z535.4 stan-dard institutes a 3 level system fordifferentiation of hazards in equip-ment. This system is already beingused by some equipment manufac-turers (industrial and farm equip-ment, heavy electrical equipment,etc.). Acceptance of the ANSI stan-dard would bring it into generalusage in the US. The use of DAN-GER on a RED label gives a feelingof urgency while NOTICE on aBLUE label does not. Broad appli-cation of these principles acrossequipment lines is important in train-ing our mobile population in fur-ther differentiation among these sig-nal words and colors.

Summarizing Key Points:l) The use of uniform key signal

words is important in telling theuser the importance of the haz-ard.Our reactions in situations re-quiring quick decisions and ac-tions is based on our lifetimeexperience and training. It is wellknown that the value of uniformsigning techniques has given toincreased safety of our U.S. free-way system.

2) The use of a recognized color toreinforce the importance of thehazard.Color is important to that largemajority of the population thatis not color blind because it con-veys additional information fromour surroundings.

3) There is some differentiation thatexists between the signal words


by Peter E. Perkins, PE

Copyright © 1991.Peter E. Perkins, PEAll Rights Reserved

One of the major objections to theproposed ANSI Hazard Markingstandard is that there is no generaldifferentiation in the populationbetween the proposed signal wordsor colors. We believe that our cur-rent data shows that there is usuallyenough differentiation between thecommonly used signal words andcolors to proceed with the introduc-tion of the ANSI standard Z535.4Product Safety Signs and Labels.

We ought to move ahead with theANSI Z535.4 standard. Our studyreinforces the usefulness of theirmultilevel system of hazard identi-fication. Within the standards set-ting efforts of companies and testhouses, movement should be to-

Hazard Markings:Signal Word and Color Perceptions


News and Notes

Copies of this document are avail-able from the U.S. National Com-mittee of the IEC, 1403 Broadway,New York, New York 10018 for acost of $35.00.

UL Ad-hoc Meeting ReportOn January 16, 1991, UL issued areport of a Ad-hoc meeting heldJuly 18 and 19, 1990 for the devel-opment of IEC 950 based stan-dards. An Appendix of the pro-posed changes to UL 1950 is avail-able. These proposals are based onTC 74 six month rule and votingdocuments.

Northeast Product SafetySocietyThe Northeast Product Safety So-ciety by mail vote in January hasadopted a constitution and is nowincorporated under the laws ofMassachusetts as an independent,not-for-profit organization. Thisconstitution does not require theaffiliation of the society with anyorganization.

A mail ballot for officers and boardmembers was conducted with thefollowing results announced intheir February 27th meeting:

President:Bruce Langmuir,

Bose CorporationVice President:

Bill Von Achen,DS&G

Secretary:Tony Nikolassy,

by Dave Edmunds

[Our readers are our greatest sourceof information. We thank you andremind you if you see a news item oran article that may be of interest tothe product safety community, pleasesend it to the Product Safety News-letter, attention: News Editor. Wewill gladly recognize the contribu-tion as yours. -Ed]

IEC Document on LaserMeasurementThe IEC has recently announced anew standard IEC 1040 entitled“Power and Energy Measuring De-tectors for Laser Radiation”. Thisdocument establishes definitions andminimum requirements as well astest procedures for the characteris-tics and the manufacturing standardsfor detectors, instruments and equip-ment for measuring power energy oflaser radiation.

The standard applies to instrumentsand equipment measuring laser ra-diation power and laser radiant en-ergy in the optical range of 100nm to1 mm.

Continued on page 9

WangTreasurer:

John Anderson,Codex (Motorola)

Board Members:Nancy Araway,

Data GeneralManfred Popp,

TÜV AmericaFrank Pereira,

IBM

The Northeast Product Safety So-ciety for approximately three yearshas been conducting monthly meet-ings with a guest speaker. The at-tendance for these meetings hasaveraged 30 people.

Low Level ElectromagneticFieldsThe EPA issued a report conclud-ing that enough evidence exists ofa possible link between cancer andlow level (60 Hertz) electromag-netic fields from power lines andhousehold appliances to warrantnew research. The study must bereviewed by high level EPA boardmembers before the conclusionsbecome policy.

UL Schedule for CourseSeminarsUL has the following courses sched-uled for UL 1950 and for Plastics:

Information Technology Equip-ment and UL 1950

May 22 - 23 in BostonJuly 30 - 31 at La Guardia


Revised Swedish Standard forTesting Visual Display Units


[The following press release is fromMPR (National Board for Measure-ment and Testing) regarding theStandard MPR 1990:8 1990-12-01(Sweden) Test Methods for VisualDisplay Units: Visual Ergonomics,Emission characteristics -Ed]

In 1985, the Swedish govern-ment ordered MPR (theSwedish National Board forMeasurement and Testing) toestablish a system for testingVDUs.

This was meant to provide the userorganizations, like trade unions andhealth organizations, with the nec-essary means to evaluate individualVDUs from the point of view ofwork health. As support for its workMPR had a reference group consist-ing of representatives from tradeunions, employers’ organizations,computer distributors’ organiza-tions, manufacturers, health orga-nizations, research institutes and testlaboratories. MPR has two expertgroups for developing test meth-ods. One for emission characteris-tics and one for ergonomic charac-teristics.

Testing of VDUs has ProvenSuccessfulThe non-mandatory testing of VDUsstarted in the beginning of 1987.The system is considered success-ful as it has contributed to the devel-opment of better VDUs in all as-pects. The test methods are used in

many countries and have won thestatus of an international standard.Laboratories wanting to have anofficial confirmation as to their ca-pability to test according to thesemethods can seek accreditation byMPR.

Test methods will not focus oncharacteristics directly related towork environmentsWhen the initial test methods weredeveloped it was decided to revisethem after a trial period of threeyears. This has now taken place.The result is that the number ofcharacteristics to be tested has beendecreased. Characteristics that werenot considered to be relevant asfactors in work environment havebeen excluded as new ones, likealternating electric field have beenadded. The characteristics testedaccording to the old methods andthe characteristics to be tested ac-cording to the new methods, to-gether with the recommended guide-lines are given in Table 1.

Documentation of methods andhandbook for usersThe new test methods are going tobe described in two documentswhich can be ordered from MPRfrom the 1st of December 1990.One of these documents contains adescription of the methods andtherefore addresses those who planto perform the tests.

The other one is a handbook for

users to help them understand andinterpret test results and their rel-evance to the work environment.

Simplified rules for accreditationDuring the first era of VDU tests alaboratory seeking accreditation fortesting VDUs had to have facilitiesto perform the complete test pro-gram or an approved subcontractorwho provided the missing facili-ties. This was considered compli-cated by many laboratories whorefrained from seeking accredita-tion for this very reason. It is nowpossible to seek accreditation eitherfor testing emission characteristicsor ergonomics characteristics. Thequality requirements for accredita-tion are however still the same.

ValidityThe revised methods will come intoforce from the 1st of January 1991.During the first half of 1991 boththe old and the new methods will bevalid. Starting from the 1st of July1991 only the new methods willapply. Laboratories seeking accredi-tation for testing VDUs have tofulfill the requirements in “MPRsGeneral Requirements For Accredi-tation Laboratories, MPFS 1990:1”.These requirements are a directapplication of the requirements inthe European standards EN 45001and 2 which specify requirementsto be met by testing laboratoriesseeking accreditation.


NewsContinued from page 6

Airport

Plastics in Electronic and ElectricalProducts

October 23 - 24 at O’HareAirport

For additional information on theseseminars, write or call UL’sNorthbrook office (708-272-8800,ext. 3444).

National Engineer’s WeekFebruary 17 to 23, 1991 was Na-tional Engineer’s Week. Fifteen en-gineering organizations sponsoredactivities with the theme “Engi-neering and our Environment”.

IEC Meeting ScheduleThe IEC central office has issued anotice that rescheduling IEC meet-ings because of events in the Gulfshould be decided by each commit-tee Secretary and Chairman afterpolling the active committee mem-bers.

The 5th General meeting of the IECis scheduled from September 30,1991 to October 12, 1991 in Madrid,Spain.

TC 74 and CBEMA Notice Re-cipients Please Note:The PSN News Editor has requestedhelp from anyone who receives theTC 74 or CBEMA committee no-tices. The editor would like to in-clude a summary of the notices inthis column, as shown in the fol-lowing example.

Example: “74(CO) 198: Because ofchanges to the power distribution inEurope, this document proposes to

revise clause 1.4.5 and 1.65. to in-clude a + 10 % and - 10 % toleranceto rated voltages of either 230 V or400 V.”

Anyone wishing to participate inthe above activity is invited to con-tact Dave Edmunds by mail in careof this newsletter.

UL Mark Puts on Weight: TheUnderwriters Laboratories symbol,a “UL” in a circle, will be looking alittle fatter in the future. Althoughthe traditional mark may continueto be used, the updated mark has athicker line. Could it be harmo-nized with the CSA mark?? AskUL for Reference Form 200-55 forrelative design and proportions ofthe UL symbol.

CSA Power Cord Labels: Thoseindividual labels on each CSA cer-tified power cord may soon startdisappearing. A new policy (Certi-fication Program Updates, Febru-ary ’91) will allow bulk labelling ormarking - similar to the UL ap-proach. The result for productsusing power cords will probably bea revision of the power cord de-scription in the CSA Report.

Coming Events:May 20 - 22, 45th Annual QualityCongress, American Society forQuality Control (ASQC), Milwau-kee, Wisconsin. The session 2.3.2,Product Safety & Inspection, isscheduled for Tuesday afternoon(May 21). The Product Safety &Liability Prevention TechnicalCommittee (of the ASQC) meetingwill be on Sunday afternoon (May19). For information call

414-272-8575.

June 12 - 13, IEEE SCV EMC ’91Colloquium, IEEE EMC Society(Santa Clara Valley Chapter), SantaClara, California. The colloquiumslogan “Product Compliance, FirstPrinciples” refers to product safetyas well as to EMC. A strong prod-uct safety program is planned onJune 12, starting at 10:00 a.m., withtalks on product liability, certifica-tion and safety engineering. Forinformation call 408-922-4444,X9346.

June 17 - 20, CSA Annual Confer-ence, Canadian Standards Associa-tion, Edmonton, Alberta, Canada.The theme this year is “CreatingQuality Environments” and manyof the sessions are oriented towardsenvironmental programs. For in-formation call 416-747-4128.

July 18 - 22, Tenth InternationalSystem Safety Conference, SystemSafety Society, Dallas, Texas. Aplethora of safety topics from thesystem point of view include pro-cess safety, safety management,nuclear safety, fire protection, prod-uct liability, software safety, ergo-nomics, and more. A special MockExpert Witness Trial will be con-ducted during the conference. Forinformation call 817-381-2562.

August 13 - 15, IEEE 1991 EMCSymposium, IEEE EMC Society,Cherry Hill, New Jersey. GenerallyEMC topics (we need a Symposiumliaison to organize a product safetysession for next year!). The Prod-uct Safety Technical Committee(TC-8) meets Wednesday morning(August 14). For information call201-992-1793.❖


by Dave AdamsHewlett PackardPalo Alto, California

The labelling requirement by OSHA(Occupational Safety and HealthAdministration) to add “NationallyRecognized Testing Laboratory” or“NRTL” to the certification marksof NRTLs (Nationally RecognizedTesting Laboratories) needs someclarification.

The problem OSHA is attemptingto solve with the marking is onetheir field officers have - “Does thismark from this test house mean theproduct is certified under the con-straints of the NRTL program?”.This problem exists because NRTLshave to apply for NRTL recogni-tion for individual product catego-ries. All the NRTLs offer addi-tional certification services (usingtheir mark) which are NOT coveredby the NRTL accreditation. OSHAinspectors can’t tell in the field whois accredited for what. OSHA thinksthat a modified mark is the answer.

The original marking requirementwas communicated by OSHA to theNRTLs. It was supposed to be imple-mented by January 1, 1991. OSHAexpected the NRTLs to communi-cate the message to their respectiveclients.

Maybe you didn’t hear from yourtesting lab? There could be a num-ber of reasons.

A) The required implementationof the marking set for January

2) UL and FM wouldn’t have tocomply until January 1994anyway.

3) Any of the NRTLs couldrequire you to use the verbiageas a matter of contractregarding use of their mark.

My data sources are:* papers from the UL/CBEMA liai

son meeting* conversations with two UL engi

neers who have heard nothing ofthe NRTL marking (verifies ULnot following the OSHA plan)

* Discussions and faxes from JimConcannon, Office of VarianceDetermination OSHA. ❖

1, 1991, has beesuspended,pending further study. OSHAstaff had an internal meetingJanuary 7, 1991, on this topic.The result was that themarking “requirement” is stillvoluntary until further notice.

B) UL and FM are“grandfathered” NRTLs untilJuly 13, 1993. The NRTLmarking only applies to thoseNRTLs who have gonethrough the formal accreditingprocess (MET, DS&G, ETL,AGA), NOT those NRTLsoperating under thegrandfather clause (UL andFM).

C) UL apparently opposes theOSHA NRTL marking idea,so they haven’t communicatedit to their customers. OtherNRTLs see a marketingopportunity here, so they arepromoting it.

D) Some testing labs are notNRTLs, so the marking doesnot apply.

If you are interested, you couldwork with UL or other NRTL to addthe NRTL verbiage to thecertification mark. OSHA will notprevent this use, regardless of howthe “requirement” is resolved.

What we have is a “marketing”issue, not a “regulations” issue atthe moment. In summary:1) OSHA marking requirement

implementation is delayed.

News ItemsNeeded!

If you see a new itemthat would be of interestto the product safetycommunity, won't you takea minute to send it to:

Dave Edmundsc/o Xerox Corp.

(MS 843 1GS)800 Phillips RoadWebster, NY 14580

(fax 716-422-7841)

—or—

Roger Volgstadtc/o Tandem Computers Inc

10300 North Tantau AveLoc 55-53

Cupertino, CA 95014(fax 408 285 2553)

NRTL Marking "Requirement"



NEMKO's Testing By Man ufacturer(TBM) Program

General Facts about NEMKONEMKO (Norges ElektriskeMateriellkontroll - the NorwegianBoard for testing and approval ofelectrical equipment) is a fully in-dependent test house, certificationbody and competence center fortechnical safety and reliability. Itmeets the stipulations of ISO/IECguides 25/38/39/40 and the EN45000 series of standards.

The sectors and types of equip-ment covered are mainly lowvoltage electrical products forhousehold, office, farming andsimilar use, such as:* Electrical installation material,* EX-equipment [Explosion

proof/hazardous locationequipment - Ed],

* Electromedical equipment,* Electromagnetic interference,* Environmental testing,* Metrology and instrument

engineering.

The scope of activities forNEMKO includes testing, certifi-cation and inspection for:* NEMKO marking of products

for the national [Norway]market,

* Statements as basis forcertification on internationalmarkets (e.g. - CCA, CB,EMKO agreements),

* Reports on special testing/inspection assignments,

* Quality systems assessment andauthorization schemes,

BasisManufacturers having adequatequalifications, facilities and qualitysystems, for conducting conformitytesting at their own laboratories andthe ability to control production toassure compliance of the finishedproducts, may apply for TBM au-thorization in order to attain certifi-cation of their products based onown measurements and investiga-tions.

The harmonization of the manufac-turers testing with the testing prac-tices at NEMKO, is based on mu-tual references (TBM-INFO), cur-rent communication and visits tothe manufacturer by the staff ofNEMKO in order to ensure correcttechnical understanding and toclarify administrative matters.

Main BenefitsReduced handling time as applica-tions will be promptly dealt with atNEMKO.Up to date knowledge of testingpractice based on close contact be-tween the testing personnel in-volved.Give the manufacturer maximumflexibility and control over the in-troduction and scheduling of itsproducts to the market.

Manufacturers must provideInformation about relevant parts oftheir organization and competenceincluding quality management ar-rangements.

* Instrument calibration,* Standardization, failureanalysis, safety research/consultancy and informationservices.

The main goals or current objec-tives of NEMKO are basically two:* Matching high technical quality

and impartiality with speedand service to satisfy clientneeds,

* Safeguarding lives, theenvironment and financialassets.

Testing by Manufacturer(TBM) IdeaThis scheme may be described ascooperation with capable manufac-turers for the purpose of rationaliz-ing type-testing of electrical equip-ment, based on special agreementand mutual trust between the manu-facturer and NEMKO. TheNEMKO TBM scheme is first of allintended for manufacturers of prod-ucts faced with rapidly evolvingtechnology and frequent productdesign changes. Manufacturers whoqualify for the TBM scheme basi-cally test and evaluate their ownproducts to ensure that they complywith applicable standards. Theymay, upon verification by NEMKO,obtain type approval and the rightto apply the NEMKO mark to com-plying products.

NEMKO’s TBM scheme was es-tablished in 1975 and today com-prises well over one hundred autho-rized manufacturers worldwide.


IEC 950: Questions and Answers

touch bare SELV parts?

Under sub-clause 2.3.4, third dashedparagraph, a wire with reinforcedinsulation appears to be accepted inthis application. Sub-clause 2.9.4specifies 0.4 mm distance throughinsulation for reinforced insulationwhen not subject to mechanicalstress, etc..

For example, is this acceptable inthe case of PVC or synthetic rubberinsulated wiring:- with 0.4 mm minimum insulationthickness,- temperature rise of which does notexceed the value given in TableXIII of sub-clause 5.1,- and which passes the electricstrength test for reinforced insula-tion?

Can the Interpretation Panel giveguidance regarding:- when insulation is considered tobe subject to mechanical stress?- if the wire would need to be anapproved component?- the need for a second protection inthe event of a single failure (i.e. -fault in 0.4 mm insulation on wire)?

Opinion of the Panel:The example you describe is ac-ceptable according to the text ofIEC 950 provided that it can beagreed that the wire is not subject tomechanical stress, etc.. This term isintended to refer to wiring which,for example, connects a hinged partto a fixed part, or is in such a posi-tion that frequent rubbing is likelyby operator functions such as load-

ing paper. Simply being exposed,for example, to occasional contactby a tool during service operationsis not considered “likely to lead todeformation or deterioration of theinsulating material”.

Regarding your other two questions,the matter of an approved compo-nent is not a matter for TC74 but israther a means for a test house toassure itself that TC74’s require-ments have been met. The insula-tion in question is Reinforced Insu-lation defined as being equivalentto Double Insulation. Only a singlefault in Double Insulation is everconsidered. Reinforced Insulationis considered to be equally reliableso that no fault can ever occur, andthe question of an additional (third)protection does not arise.

Question (11 September 1989):Is it part of the procedure for theoperation of the Chairman’s Advi-sory Panel that the answers to ques-tion be sent to certain bodies forinformation (e.g. - IECEE Com-mittee of Testing Laboratories)? Ifso, is this being done?

Opinion of the Panel:Yes. The answers to date will shortlybe distributed to test houses andothers.

[There are more questions and opin-ions in the package distributed, someof which may appear in future is-sues of the PSN. Here’s a questionfor our Readers - Did you know thatthis Panel existed? - Ed.] ❖

Here are some questions and an-swers for use with IEC Standard950, Safety of Information Tech-nology Equipment, from the TC74Chairman’s Advisory Group (for-merly Interpretation Panel).

The following notes should be readin conjunction with opinions ofthe Panel.

1. The Panel consists of activemembers of TC74, but its opinionsare those of the Panel and are notvoted decisions of the IEC.2. Where it is felt that a query arosedue to lack of clarity in a standard,the matter will be brought to theattention of the appropriate groupon TC74.3. Panel opinions are restricted tointerpretation of the words of thestandard in question, as the mem-bers of the Panel recollect the origi-nal intentions of TC74. The Panelcannot be concerned with the appli-cation of the standard by test agen-cies and approval authorities.4. The use made of Panel opinionsby the originators of requests forinterpretation, and others, is theirown responsibility, and no guaran-tee can be given that a subsequentamendment to the standard will sup-port their opinion. To assist inassessing the reliability of their opin-ion, the Panel will state whether it isunanimous or otherwise.

Question (19 January 1988):Under IEC 950: 1986, is it accept-able for a wire at hazardous voltagewith one layer of insulation, with aminimum thickness of 0.4 mm, to


Under IEC specifications effective in 1992,power supplies rated above 300 W need power-

factor correction to avoid the Class D label.

ing an input current with a “specialwave shape.”

While Class A power supplies havea maximum permissible harmoniccurrent of 2.3A in the third har-monic, Class D power supplies arelimited to a maximum permissibleharmonic current of 1.08A in thethird harmonic—a significant dif-ference.

The IEC 555-2 specification callsfor equipment to be deemed ClassD if the input current’s wave shapeof each half-period— referred to asits peak value, i(pk), is within theenvelope of the accompanying fig-ure for at least 95 percent of theduration of each half-period. Thecenter line M coincides with thepeak value of the current. The fig-ure shows the “special wave shape”with a typical uncorrected wave- Continued on page 19

by Arnold Hagiwara,Vice President Pioneer Magnetics,Santa Monica, CA.

Beginning in 1992, new regulationsrecommended by the InternationalElectrotechnical Commission (IEC)go into effect in Europe, toughen-ing requirements for power sup-plies. Included in these regulationsare sections limiting the harmoniccurrent for all electrical and elec-tronic equipment sold with an inputcurrent of up to 16 A and nominalvoltages of up to 240 V; singlephase, two or three wire; or nomi-nal voltages of up to 415 V, three-phase, three or four wire.

U.S. manufacturers should be con-cerned with these standards for tworeasons. First, to sell power sup-plies or equipment using power sup-plies in Europe after these regula-tions take effect, U.S. manufactur-ers will have to meet the tougherstandards. Second, many believethe Canadian Standards Associa-tion and UL won’t be far behind inadopting similar rules.

The EC 555-2 standard coveringharmonic-current limitation dividesequipment into four classes.Class A covers balanced, three-phase equipment. except for equip-ment covered in one of the otherclasses.Class B governs portable tools.Class C covers lighting equip-ment, including dimmers. Finally,Class D includes equipment hav-

Power Factor Correctionfor European Use

form and a typical corrected wave-form superimposed on it. Withoutsome form of power factor correc-tion, the power supply would fallinto the tougher, more restrictiveClass D. Even if classification is nota concern, power-factor correctionis generally advisable because, with-out it, harmonic distortion couldlower the available power to thesupply.

Uncorrected Power Factor Lim-its Output Power and IncreasesLine-Current HarmonicsPower factor is the ratio of truepower to apparent power. A resis-tive load has a power factor of one(the highest possible) because itscurrent waveform is identical to,and in-phase with, its voltage wave-form. When a load is not purelyresistive, its current waveform is


RevisedContinued from page 7

TABLE 1Characteristics tested Characteristics to be testedaccording to the old methods according to the new methods New Guidelines

Visual ergonomic properties Visual ergonomic properties1.01 Polarity1.02 Background/character 1.02 Background/character

color color1.03 Screen/cursor luminance 1.03 Screen/cursor luminance >100 cd/m2

1.04 Mean luminance 1.04 Mean luminance1.05 Luminance uniformity 1.05 Luminance uniformity •80%1.06 Reflex sensitivity, 1.06 Reflex sensitivity, <1%

specular specular & partly spec.1.07 Reflectance, diffuse 1.07 Reflectance, diffuse <10%1.08 Image trace decay after

change of character1.09 Jitter 1.09 Jitter 0.0002 mm/mm1.10 Calculated critical 1.10 Calculated critical CFF

flimmer frequency flimmer frequency1.11 Character distortion 1.11 Character sizes, <10%

character distortion1.12 Number of pixels in

character image “H”1.13 Character sizes (“H”)1.14 Linearity <(1%)1.15 Orthogonality <(1%)1.16 External and internal 1.16 External and internal >70%

luminance modulation luminance modulation1.17 Angle-dependent 1.17 Angle-dependent max 25% vid 40°

luminance modulation luminance modulation1.18 Raster modulation 1.18 Raster modulation - <15%

raster frequency >65%1.19 Line definition: 1.19 Sharpness/

MTF analysis MTF analysis

Emission properties Emission properties2.01 X-ray radiation 2.01 X-ray radiation2.02 Electrostatic potential 2.02 Electrostatic potential ±500 V2.03 Induction2.04 Magnetic field 2.04 Magnetic field

2 kHz - 400 kHz -25 nT @ 50 cm


Emission properties (cont.) Emission properties (cont.)5 Hz - 2 kHz -250 nT @ 50cm

2.05 A-weighted sound level2.06 Sound intensity level in

the 16 kHz octave band2.07 Heat emission

Alternating electric fields2 kHz - 400 kHz -2.5 V/m @ 50cm5 Hz - 2 kHz -25 V/m @ 50cm

(in front)

Physical design Physical design3.01 Vertical tilt3.02 Adjustment for height3.03 Placing of controls3.04 Reflectance 3.04 Reflectance

(screen casing)3.05 Dimensions3.06 Weight

Ergonomic properties1.01 Height of cross-section1.02 Angle of slope1.03 Pressure to depress key1.04 Friction against undrlay

Physical design2.01 Dimensions2.02 Weight2.03 Placing of keys2.04 Grouping of keys2.05 Design of keys

Other properties Other properties3.01 Size of characters

on keys3.02 Sensitivity to reflexes

of the keys3.03 Connecting cable3.04 Electrostatic run-off 3.04 Electrostatic discharge


Class 3A to include non-visible la-sers having an output power of 5times the AEL for Class 1.JUSTIFICATION: Harmonizationwith IEC 825 and ANSI Z136.1.

9. Revise the requirements for spe-cific labeling in the CDRH standardto specifically allow the IEC sym-bols as an alternative to the DAN-GER and CAUTION labels.Arabic numerals shall be used in-stead of Roman numerals for classes.JUSTIFICATION: Harmonizationwith IEC standard 825 and ISOsafety labeling standards.

10. Delete the requirements for in-terlocks on access panels whereaccess only allows exposure tolevels of laser radiation less thanClass 3A. (This change would in-clude IR wavelengths as per pro-posal #8 above.)JUSTIFICATION: Harmonizationwith IEC 825.

11. Eliminate the requirements forcollateral radiation, so that CDRHcould always rely onthe defectprovision of the standard if therereally was a significant hazard. Thiswould eliminate Table 6 for AEL’sfor collateral radiation.JUSTIFICATION: Harmonizationwith IEC 825 and to make measure-ment and compliance with the stan-dard more straightforward.

12. Eliminate the requirement for abeam attenuator for Class 3A andlower. (This changewould in-clude IR wavelengths as per pro-posal #8 above.)JUSTIFICATION: Harmonizationand performance feature not reallyused.

LaserContinued from page 3

13. Adopt the N-1/4 repetitive-pulserequirement for Class 1 AEL’s(thereby also applyingindirectly toClass 2 and 3A) as currently exist-ing in the ANSI Z136.1 and IEC825 (with proposed revision). Thisproposal is mutually inclusive withproposals #1 and #7 above.JUSTIFICATION: Bring 21 CFR1040 into agreement with more re-cent biological data and harmoni-zation with IEC 825.

14. Adopt the IEC wording for emis-sion indicator in current standards:“. . . give an audible or visiblewarning when the energy source isactivated or if capacitor banks ofpulsed lasers are being charged orhave not been positively discharged. . .” Consider adopting changesnow being considered by WG1 forrequiring emission indicators onmultiple or remote apertures.JUSTIFICATION: Improved word-ing, harmonization with IEC.

RECOMMENDED CHANGESTO IEC 82515. Add requirements for interlockson access panels where access al-lows exposure to levels of laserradiation exceeding Class 3A.JUSTIFICATION: Concern withpotential hazards of viewing haz-ardous laser radiation emitted fromopened enclosures in Class 3B andClass 4 laser products. It isf e l tthat even though eye protectionwould be worn with Class 3B and 4laserproducts, maintenance of anotherwise enclosed laser systemmight not require the use of lasereye protection.

16. Add the concept of permitting

ProductSafety

AbstractsNeeded!

Please send yourproduct safety ab-

stracts to:

Dave Lorusso MS PS-1c/o Codex Corporation

4 Conlyn AvenueFranklin, MA 02038

an alternative means of protectionto the beam attenuatorfor Class 3band 4.JUSTIFICATION: The beam at-tenuator is normally not relied uponfor very high power lasers and maybe impractical.

17. Request the addition of a manualreset for power interruption of Class4 lasers.JUSTIFICATION: Where lasershave been shut down by interlockinterruption of main power or by ageneral power failure.

18. Clarify that the beam attenua-tor, emission indicator, key switch,and remote interlockconnectorsrequirements apply only to laserproducts and not to laser systems.JUSTIFICATION: WG1 recom-mended this to avoid needless in-stallation on OEM laser systems,etc. ❖


Editorial,Continued from page 1

MarkingsContinued from page 5

Have you done so? Better check!

Standards and MoreStandards are presently hot topicsfor product safety engineers, espe-cially those concerned about theharmonization of standards in Eu-rope for 1992. The question that ourStandards Subcommittee is address-ing is NOT “How do we make an-other flavor of IEC 950?”, but rather“Are there some areas where a newstandard would help productsafety?”. If you have opinions aboutthis topic, and suggestions that aWorking Group could sink its teethinto, Tania Grant (408-957-7877)wants to hear from you.

Another topic that concerns Tech-nical Committees - Conferences andSymposia - has some good newsand some bad news to report. Thegood news is that the regional Col-loquium sponsored by the SantaClara Valley Chapter of the EMCSociety in June will have a sessionon product safety. The bad news...excuse me, the OPPORTUNITY isthat we have a position to fill forLiaison with the EMC Society Na-tional / International Symposium.This vacant position, ably handledlast year by John Knecht of Under-writers Laboratories, prevented ourplanning a separate product safetysession for New Jersey in August.Please call Brian Claes (408-285-4768) now if you can help with theNational Symposium in Los Ange-les in 1992! (And what about Texasin 1993?)

Continuing news is that various lo-cal groups are becoming more (oroccasionally less) active, as the Santa

Clara Valley regional Colloquiummight suggest. The Central Texas(Austin) group is coordinating meet-ings with the local EMC SocietyChapter after a lull in activity whenthe original organizer, GeorgeJurasich of TÜV Rheinland, trans-ferred to Singapore. The North-eastern group in Boston decided totry forming a separate incorporatedSociety immediately, instead ofworking up through TechnicalCouncil status to form a Societywithin the IEEE. Of course, indi-vidual members are still membersof the IEEE and the EMC Societyand continue to participate in TC-8activities. The new San Diego grouphas developed strong local interest,meeting topics and attendance andis off to a great start.

What’s Next?Many of our ongoing activities forthe next year have already beenmentioned, but perhaps I can sum itup. First, the Product Safety News-letter plans to become stronger, bothtechnically and financially. Thiswill let it become the forerunner ofthe technical journal we intend topublish after becoming a TechnicalCouncil. Second, support is beingsought from other IEEE Societiesto form a Technical Council forProduct Safety. The EMC SocietyBoard of Directors formally ap-proved that goal at their August,1990, meeting. Third, standardsactivities should be increased andorganized. Fourth - or perhaps first- more participation is needed to beable to achieve the other three goals.Join us!

Submitted by John McBain, PSTCSecretary/Treasurer, 3/18/91❖

commonly used.Our data shows that there is adifference in the understandingof the hazard associated withthese signal words surveyed. TheFMC manual or theWestinghouse manual are thebest examples of hazard mark-ings that are in line with theANSI proposal.

4) There is also some differentia-tion between the colors com-monly used. The people sur-veyed do distinguish a range ofurgency associated with thesecolors. This reinforces our com-mon perception.

Reviewing the ProblemThere are two key elements of anyhazard markings that appear onequipment; these are the signalwords used and the color of thehazard marking itself. Do peopletoday differentiate enough betweenthe commonly used words or colorsto make them useful? What do wethink when we see the word DAN-GER or the color YELLOW?

By now, many people have noticedthe change hazard markings foundon some equipment. A prominentexample is the marking used on padmounted electrical transformersfound in many neighborhood wherethe power is underground.

Our business community needs tosee these results since adequate haz-ard markings is a big product liabil-ity issue. One of the three key waysa manufacturer can get into troubleis to have inadequate hazard mark-ings on their equipment. In review-


NEMKOContinued from page 10

ated by those using it, and that aforeseeable use of the product willbe dangerous without that knowl-edge, the manufacturer is under anaffirmative duty to give reasonablewarning about such condition orhazard and instructions for safeuse.”1

The interest here is in determiningwhether or not there is a perceiveddifference between the words used(DANGER, WARNING, CAU-TION or NOTICE) or the colorsused for the marking itself (RED,ORANGE, YELLOW or BLUE).

Additional QuestionsAn area that is still unclear is howwell training would reduce the un-certainty in the use of these signalwords and colors. The range of re-sponse overlaps. The signal wordswe are looking at here are DAN-GER, WARNING, CAUTION andNOTICE The colors we are re-viewing are RED, ORANGE, YEL-LOW and BLUE. These are thewords and colors recommended bythe proposed ANSI Z535.4 stan-dard. There is apparently no widelyavailable information on the ratingof the signal words or colors bothbefore and after training.

Consistency in the use of these sig-nal words and colors will providethe reinforcement desired for theuser community at large. The adop-tion of the ANSI standard would bea major step in that direction. As wesee a consistent set of signal wordsand colors used on common items,we will better understand the im-portance of each of them.

1Bass, Lewis ‘Products Liability, Design and

Manufacturing Defects’, 1986, Shepard’s/

McGraw-Hill, Inc., Colorado Springs, CO. ❖

ing any accident for a potential prod-uct liability claim, the legal teamwill carefully look at the hazardmarkings on the equipment to as-sess if they deem them to be inad-equate. If so, they will feel that theyhave a case.

Our ResultsThese results show that there is somedifferentiation in the use of thewords or colors. The difference isnot absolute, since there is a widerange of responses. This is not sur-prising since there is not any consis-tency in the range of colors or signalwords in use today. UL (Underwrit-ers Labs) usually uses a two levelset; Danger and either Warning orCaution. ANSI is recommending athree level set, using all of thesewords. Acceptance of the ANSIstandard would set the three levelsystem in place. There are continu-ing questions as to whether there isany differentiation between thesewords or colors. This survey is anattempt to find out. The same ques-tions arise with respect to the colorsused.

We have surveyed a few folks re-garding this differentiation. Wewant our product safety communityto see that there is some differentia-tion that exists without extensivespecial training. Describing the dif-ferences between hazards is alreadyunderstood by many people.

A good rationale is given by Bass:“The underlying principle in failureto warn cases can be stated as fol-lows:Where the manufacturer can fore-see that the condition or hazardouscharacteristics of the product arenot likely to be known or appreci-

Manufacturers must haveQualified testing personnel withworking knowledge of applicablestandards and test methods(NEMKO, IEC, EN, etc.).Necessary test equipment withproper characteristics and toler-ances.Calibration procedures to appropri-ate reference standards which inturn are identified as traceable tonational or international calibrationstandards.A qualified program to control de-sign, product verification, produc-tion and testing activities. (Prefer-ably based on the ISO 9000 seriesand ISO/IEC Guide 25 and respec-tively the EN 29000 series and EN4500 in Europe).

Authorization and workingprocess — Initial PhaseIntroductory visit including infor-mation collection and general sur-vey.Testing results correlation

Acceptance PhaseSigning the authorization agreementwhich confirms that the manufac-turer qualifies for the TBM-scheme.NEMKO’s type approvals of theproducts are then currently basedon the manufacturers own data andtest reports.

Follow Up PhaseIn order to maintain a sound basisfor the TBM-cooperation,NEMKO’s staff will visit the manu-facturer normally once a year tocarry out surveillance and exchangeessential information. NEMKO will


provide the manufacturer with up-dated TBM-INFO’s describing theterms of preference for testing ofthe applicable equipment catego-ries. Less frequent or more frequentvisits may however be appropriateand be subject to current agreementbetween NEMKO and the manu-facturer.

Multinational Certification :NEMKO is taking active part in theNordic (EMCO), European (CCA)and international (IECEE/CB) cer-tification cooperation agreementsand may issue certified reports tosimplify the certification/approvalprocess in other countries. In suchcases, samples must be provided toNEMKO for verification and nec-essary testing (or alternatively atthe manufacturers premises undersupervision of NEMKO personnel.)However, base on the TBM-scheme,NEMKO offers the manufacturersfirst priority handling of applica-tions and a service degree thatshould serve the clients needs,whether it concerns certification forNorway only or multinational certi-fication.

CostsThe manufacturer or his represen-tative will have to cover all costs inconnection with necessary visits tothe manufacturer. Visits will how-ever be coordinated and organizedin such a way that the costs as far aspossible can be shared between dif-ferent manufacturers in the samearea.

From 1991, an annual charge ofNOK 5000 (approx. USD 850) isintroduced to cover NEMKO’s costsassociated with the contingency,administration and technical infor-

Some additionalfacts about

NEMK O's TBMprogram

As of early March:NEMKO had83 European

32 USA37 Far East

manufacturersparticipating in TBM.

NEMKOProfile:

150 employees of which100 are directly involved

in Testing andCertification.

In 1990, approximately18,000 projects were

opened of whichapproximately 15,000resulted in Certificates

or Approvals.

NEMKO hasapproximately 60,000type approvals listed

NEMKO hasapproximately 2,300

clients

mation services involved.

Option: Quality SystemAssessmentAs NEMKO personnel involved hasbeen particularly trained in the ISO9000 series and corresponding au-diting techniques, we may also of-fer full assessment of manufactur-ers quality systems to ISO 9000.This may either be associated withor separate from the TBM authori-zation - and may ultimately lead toaccredited certification of the manu-facturers quality system in line withfuture European conditions.

Key PersonnelKey personnel in NEMKO to con-tact for further information aboutthe TBM-scheme and quality sys-tems assessment: Leif Nybro (Elec-tronics), Grim Langås (Appliances),Nils Bøvre (Lighting equipment andinstallation material) at the follow-ing address:

NEMKONorges Elektriske Materiellkontroll(Norwegian Board for testing andapproval of electrical equipment)

Office address:Gaustadalleen 30,0314 OSLO 3

Postal address:NEMKOBoks 73 BlindernN-0314 Oslo 3NORWAY

Telefax:int + 47 2 69 86 36

Telephone:int + 47 2 69 19 50 ❖


CorrectionContinued from page 12

out-of-phase with, or different from,its voltage waveform. In this casethe power factor is less than unity(see Fig. 1).

A switching power supply repre-sents a nonlinear load and draws apulse current whose waveform dif-fers significantly from the inputvoltage waveform (see Fig. 2). Thispulse current consists of fundamen-tal and harmonic current compo-nents. Only the fundamental cur-rent component, whose waveformmatches the input voltage wave-form, will contribute to the powerused by the power supply. The har-monic components contribute to theRMS line current, but not to theusable power.

There are two considerations thatmake power factor correction de-sirable:1. Maximizing the wattage avail-

able to drive the system given the80% limitation on allowable cur-rent in a branch circuit.2. Minimizing the harmonic distor-tion to insure compliance with pend-ing legislation.

As the power factor increases, therequired input RMS current de-creases for a fixed output powerlevel. Therefore, more useful powercan be obtained from a set linecurrent. Output power (Pout) is de-fined as:

Vin(rms) x Iin(rms) x PF x Efficiency

If the available line current Iin islimited, the useful power outputcan be increased if the Power Factorx Efficiency (PFE) product is d Ona 15-ampere service, U.L. the drawto a maximum of 1440 VA (120VAC x 12 A) If the power supply is70% efficient, and the power factoris 0.65, the PFE product equals 0.46,allowing a maximum output of 655watts. By increasing the PFE prod-

uct to 0.7, the power output in-creases to 1007 watts—a 54% in-crease.

High harmonic currents typical inswitching power supplies result inpoor utilization of the power distri-bution system (power companieshave to generate the RMS currenteven though it is not usable by theload). As an example, circulatingcurrents in the delta windings ofthree-phase power distributiontransformers can cause temperaturesin these transformers to rise to fullload values well before they reachtheir full load power levels. Also,these currents cause additional stresson fuses, circuit breakers, wall sock-ets and wiring. Most significantly,the high energy content of thirdharmonic results in the neutral wireof the three phase power grid beingsubjected to a 70% overload . As aresult, governmental agencies havebegun to set standards limiting har-monic current content of electronicequipment. ❖


We are grateful for the assistance given by these firmsand invite application for Institutional Listings fromother firms interested in the product safety field. AnInstitutional Listing recognizes contributions to sup-port the publication of the Product Safety Newsletter ofthe IEEE EMC Society Product Safety Technical Com-mittee. Inquiries should be send to: The Product SafetyNewsletter, C/O John McBain (M/S 42LS), Hewlett-Packard, 19447 Pruneridge Avenue, Cupertino, CA95014.

InstitutionalListings

We grateful for the financial

support of the organizations

listed here.


Contact the Product Safety

Newsletter to have your List-

ing placed in the next issue.

March meeting of the Portland andSeattle area groups featured BobPollock of UL. Bob spoke on thedouble insulation requirements inUL 2097. Great slides and a goodquestion and answer period fol-lowed.

Future meetings are noted in theArea Activities Calendar, Page 22.For more information about thePortland activities, please call FranPelinka at 503-641-4141. Moreinformation about the Seattle ac-tivities may be obtained by contact-ing Walt Hart at 206-356-5177.❖

Santa Clara Valley:The February meeting featured Mr.Leif Nybro who covered the Nor-wegian Product Safety agency’s(NEMKO) testing program formanufacturers. Please refer to thearticle on page 10 of this newslet-ter.

The March meeting featured a pre-sentation by Gary Fujii of UL onUL 1459. Gary basically wentbriefly over the latest edition andrelevant bulletins of the standard,the Definitions, and constructionand test requirements. The latestrevision to the standard dated March

8, 1991, has many pages of revi-sions and incorporates the require-ments from earlier bulletins. Garyalso covered requirements in thestandard that often prove to be pit-falls to manufacturers.

Future meetings are noted in theArea Activities Calendar, page 22.For more information about theSanta Clara Valley activities, pleasecontact David McChesney at 408-985-2400, extension 2771.

Portland/Seattle:According to Fran Pelinka, the

Area Activity Reports


� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

Area Activities Calendar� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� April

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� May

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� June

Central TexasVic Baldwin

(512) 469 7289

David Staggs (512) 343 3751

Thursday, April 25, 8PM "Safety and EC92"

Jim deVries Dell Computer

Location: New Braumfels

Thursday, May 23, 8PM "ESD and Susceptibility"

Warren Boxleitner KeyTek

Thursday, June 20 No Meeting Scheduled

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� Chicago

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

Dick Hagedorn (708) 505 5722

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

Call for Information � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

Call for Information � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

Call for Information

Orange County Southern California

Filenet Corp., Bldg 3 1550 Scenic Ave. Costa Mesa, CA

Ercell Bryant

(714) 966 3459

Tuesday, April 2, 6PM "UL Plastics Program"

Bob Schmidt Underwriters Laboratories Inc

Tuesday, May 7, 6PM "Review of CBEMA Meeting"

Charlie Bayhi and others

Tuesday, June 4, 6PM Topic and Speaker TBD

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� Portland

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

PGE Co. 14655 SW Old Scholls Ferry Rd

Beaverton, OR 97005

Fran Pelinka (503) 641 4141

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

Tuesday, April 16, 6PM "CSA Checklist"

Paul Fabrey CSA

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

Tuesday, May 21, 6PM "Power Quality"

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

Tuesday, June 18, 6PM "Plastics" Jim Pierce

ETL

San DiegoHP Cafeteria

16399 West Bernardo Rd. Rancho Bernardo, CA

Scott Bonnet

(619) 592 4571

Wednesday, April 3, 6PM "UL Plastics Program"

Bob Schmidt Underwriters Laboratories Inc

Wednesday, May 1, 6PM "Product Safety Liability"

Rick Schneider Attorney

Wednesday, June 5, 6PM Topic and Speaker TBD

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� Santa Clara Valley

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

Apple Computer Inc 20705 Valley Green Drive

Cupertino, CA

John Reynolds (415) 335 1344

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

No Regular Meeting Scheduled� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

Tuesday, May 28, 7PM "EMC Directives, Conducted and

Susceptability" Leo Makowski

Haefely Test Systems

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��

No Regular Meeting Scheduled

SeattleJohn Fluke Mfg., Co. 6920 Seaway Blvd.

Everett, WA

Walt Hart (206) 356 5177

Wednesday, April 17, 6PM "CSA Checklist"

Paul Fabrey CSA

Wednesday, May 22, 6PM "Power Quality"

Wednesday, June 19, 6PM "Plastics" Jim Pierce

ETL


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c/o Tandem Computers Incorporated10300 North Tantau Avenue, Loc 55-53Cupertino, CA 95014Attn: Roger Volgstadt

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