WWW.DISSERTATION.XLIBX.INFO
FREE ELECTRONIC LIBRARY - Dissertations, online materials
 
<< HOME
CONTACTS



Pages:     | 1 |   ...   | 3 | 4 ||

«Solid-State Lighting Product Quality Initiative SECOND EDITION JUNE 2011 Next Generation Lighting Industry Alliance with the U. S. Department of ...»

-- [ Page 5 ] --

The working group recognizes that these measurements are expensive and time consuming, and not all manufacturers may have the ability to comply when the product is first introduced. If the recommended minimum confidence level is not achieved, manufacturers may prefer to warrant performance for a specific period of time instead of making a specific lifetime claim. In that instance, the working group recommends stating the number as a “warranted lifetime,” as distinguished from a substantiated lifetime estimate.

When specifying a product’s L70 lumen maintenance claim of B50 lifetime, or any other value, the manufacturer should validate the product life not only upon first release, but also in the event of any changes to the product during its lifetime. Such changes may relate to design (which includes product variants), component, subsystem material, supplier, or manufacturing process—in short, anything that may affect product life.

The rest of this section addresses some of the necessary steps to demonstrate a product’s lumen maintenance life claim by separately considering a new platform, and then how to deal with variations in that platform. While some examples are shown, they are not intended to specify a standard procedure. Responsibility for specific standards lies with standards organizations and is beyond the scope of this guide.

NEW PLATFORM LUMEN MAINTENANCE

The preferred tool for measuring performance of LED systems is IES LM-79-08 Approved Method:

Electrical and Photometric Measurements of Solid-State Lighting Products. LM-79 prescribes uniform test methods under controlled conditions for photometric and colorimetric performance as well as electrical power measurements for LED fixtures as they would be manufactured for production. A key systemic element of LM-79 is that the LED fixture must be tested using absolute photometry which measures LED performance in situ.

For a new platform it is the manufacturer’s responsibility to demonstrate life performance compliance by testing luminous flux, in accordance with LM-79, in a sufficient sample of product for a sufficient amount of time to have confidence in the lifetime figures.

–  –  –

Summary table showing in lumen maintenance (percent) change in input power (percent), and change in color after 6,000 hours of testing • LM-79 reports at T = 0 and T = 6,000 hours Description and details of the product under test and test setup •

–  –  –

Although extrapolated LM-80 data for packaged LEDs has been used as a proxy for luminaire lifetime (and is an ENERGY STAR requirement), it only deals with lumen depreciation of a luminaire indirectly, and then only depreciation due to the LEDs themselves. There is also an issue regarding how to accurately extrapolate data of limited duration. The TM-21 committee of the Illuminating Engineering Society of North America (IES) has been exploring ways to address the latter. As of this writing, the results of the committee’s work have not been published, but when available, they may be used to extrapolate to the L70 value of the LED packages, but not for the luminaire. The working group therefore recommends LM-79 testing of the complete luminaire to determine lumen output over time.

PRODUCT VARIATION OF NEW PLATFORM

Recognizing possible platform variations to extend the product line for other applications (product groups) or material or design changes, additional measurements may be needed to ensure the platform is still qualified. Consideration may be given to minimize the number of test hours to demonstrate long-term life performance, as described above. In this regard, it is reasonable to consider the different types of change (or model variations) and their likely impacts on lifetime.

Ultimately, this is the customer’s choice, but it is recommended that manufacturers develop and document specific rules for change control to maintain the integrity of their products.

For example, changes in the following areas may be deemed to require significant retesting:

Housing/chassis Thermal management/heat sink • Change of assembly method or materials • Light source (includes operating current, Vf, and LED supplier) •

–  –  –

Other changes, such as in finish or out of the optical path, may require less requalification.

Analytical data may often be used in part to demonstrate that the change has not influenced the luminaire’s lumen maintenance performance. But typically, a small number of luminaires may need to be retested for some, perhaps shorter, period of time. If the manufacturer cannot demonstrate via analytical data or limited testing that life performance is not diminished, then the luminaire should be treated as a new platform and subject to full qualification requirements.

LED Luminaire Lifetime Recommendations, June 2011 Page 25 The working group recommends that manufacturers develop and document their own change control process, and that they be responsible for providing sufficient justification to their customers so that any change will be accepted as having no material, deleterious effect on product lifetime.

ADDITIONAL CONSIDERATIONS





The discussions above outline current understanding of the issues surrounding LED luminaire reliability and lifetime. A basic recommendation for a standard, default designation of product life is provided, along with some suggestions for additional characterization in certain applications or markets. During the course of discussion to update this guide, the working group considered a

number of additional aspects of product lifetime, namely:

Design for system reliability Product labeling •

Warranties • •

DESIGN FOR SYSTEM RELIABILITY

A thread running through many working group conversations was that the methods available today to demonstrate full luminaire performance over time (using LM-79) may be too costly or timeconsuming to be practical in many circumstances, especially given the rapid evolution of SSL products. The result is often a fall-back to the use of LED package lumen depreciation as a proxy for product lifetime, and the fear is that this will lead to customer dissatisfaction with this new and promising technology.

LED operation is interdependent upon drive electronics, the thermal management system, and the optical system, as well as upon proper and controlled materials and manufacturing processes.

Because of the resulting complexity, it may be more efficient and effective to take a system reliability approach in the design of the LED lighting fixture. By understanding how each system component contributes to failure, one can estimate overall reliability and optimize the design for best performance. Figure 4 (page 11) simply illustrates how information on various individual parts of the system can be combined to arrive at an overall estimate of lifetime. If statistical information on failures were available even for the major subsystems of a luminaire, it would be a big step toward more realistic estimates of product lifetime. While this would not obviate the need to verify lifetime anytime soon, it could eventually reduce the overall testing requirements.

As noted earlier, however, some failure modes may be as a result of interaction between parts of the system, which requires still more sophisticated analysis. For example, LED manufacturers typically use pulse-mode operation with a very short pulse—typically 10 or 20 milliseconds— which will not heat up the LED. On the other hand, there may be numerous LEDs in situ, often in close proximity to one another, operated continuously. These conditions elevate TJ above 25°C, thereby affecting photometric and colorimetric performance of the LEDs. This effect is offset by LED Luminaire Lifetime Recommendations, June 2011 Page 26 various thermal management approaches incorporated into the luminaire design, which must be accounted in the system reliability design.

The DOE SSL Manufacturing Roadmap recommends that LED driver manufacturers provide uniform data for LED fixture manufacturers which include a number of specific performance results to assist in luminaire design. A similar approach might also be applied to other components and materials.

Once such information begins to become available, software to analyze and combine the data into an overall system reliability estimate will be needed. The working group believes that the industry working together to arrive at standard methods to report and process statistical reliability information could be highly beneficial in terms of the effort and cost needed to achieve reliable product design, as well as the accuracy of the resulting lifetime predictions.

–  –  –

lifetime, L70/B50, as defined in this guide. Recognizing that some manufacturers may not have the The DOE Lighting Facts® label should be augmented to include the standard LED product ability or time to demonstrate lifetime in accordance with these recommendations, the label should not require that lifetime be stated, but if it is, then it should be reliably established with standard tests. Otherwise, a specific lifetime should not be claimed at all. If lifetime is not stated, then it is recommended to include at least one of these other options: lumen depreciation, a warranty, or an estimate based on accelerated testing of components.

The label should also be augmented to indicate whether the product is “serviceable” or “nonserviceable” as defined in this guide.

–  –  –

The DOE Lighting Facts label should also be modified to include, optionally, a warranty period to cover either lumen lifetime, color shift, or both. The warranty period may or may not coincide with lifetime (if claimed) at the manufacturer’s discretion. This warranty may be particularly useful to manufacturers who, while not able to demonstrate lifetime in accordance with the recommendations, are nonetheless prepared to guarantee performance over some period of time.

This may be especially useful for new products, also.

Absent lifetime data as prescribed, the manufacturer may alternatively or in addition to a warranty state the LED lumen depreciation time to L70 based on LM-80 data and a projection based eventually on TM-21. Because present practice is often to use this figure as a proxy for lifetime,

however, the label should be explicit:

The time shown should be described as “LED lumen depreciation to L70,” not as lifetime. Moreover, this depreciation time value should only be shown if the manufacturer “Lifetime,” and should avoid any implication that it represents tested product can assure that the LEDs are operating at or below the temperature of the LED LM-80 testing used to project the designated value, and that the drive current in the luminaire does not exceed that used for LM-80 testing during the stated time period. Additional information that should be readily available to the purchaser, although not on the label itself, should include maximum ambient temperature of operation to achieve this LED Luminaire Lifetime Recommendations, June 2011 Page 27 depreciation performance, the number of hours actually tested on which the projection is based, and the type of projection if not in accordance with TM-21.

If a manufacturer has developed proprietary techniques for accelerated component testing and system modeling, as suggested in the previous section, then it may choose to designate an “estimated system life” on the label. In no case should this figure exceed the lumen depreciation period estimate, however.

The Lighting Facts program may require substantiation of any lifetime claim put forth for use on the label. In addition, the burden of proof lies with the manufacturer to show that any platform changes have not materially affected lifetime.

The label should further be modified to include, optionally, certain color shift information

depending on the market segment:

A general qualitative description of color shift, or A maximum color shift warranted for some period of time, or •

–  –  –

For the short term, color shift, if quantitatively specified, could be described in terms of change in CCT. For some applications, and for professional use, actual limits on the change in color coordinates should be specified, but it is not recommended to include them on the Lighting Facts label.

Since the original publication of this guide, the Federal Trade Commission has developed requirements for a label similar to Lighting Facts for certain replacement lighting products. While this label has the same name, it is formulated somewhat differently, which may lead to some confusion. The working group hopes that the FTC adopt the same definition of lifetime as recommended in this guide, if possible, to preserve a degree of uniformity among products and labels.

THE ROLE OF WARRANTIES

Given the early stage of LED lighting technology, it is difficult to accurately predict product lifetime.

Warranties provide a means for the potential buyer to reduce risk. While this guide provides some guidance on what might be included in a warranty, it is ultimately the manufacturer’s decision on how best to provide this protection and how much risk to take in doing so. The warranty may logically be shorter than the standard lifetime as defined in this guide. As there will be a distribution of failure times for any product, the degree of risk on the part of the manufacturer depends on the level of confidence in the projected lifetime and the amount of variation in that distribution.

LED Luminaire Lifetime Recommendations, June 2011 Page 28

RECOMMENDED FURTHER READING

Benatti, John. “MTBF and power supply reliability.” Electronic Products, August 1, 2009.

IPC-9592A, “Requirements for Power Conversion Devices for the Computer and Telecommunications Industries.” Mao, George and Marshall Miles. “LED driver lifetime and reliability hold the key to success in LED lighting products.” LEDs Magazine, September/October 2010, 33–37.

Weiss, Bill. “Lighting for Life.” Digi-Key TechZone, TZL101.US (November 11, 2010), 8–14.

LED Luminaire Lifetime Recommendations, June 2011 Page 29

ACKNOWLEDGEMENTS

The Department of Energy and the Next Generation Lighting Industry Alliance wish to acknowledge the valuable contributions of the members of the DOE Reliability and Lifetime Working Group who offered their considerable time and expertise to the development of this document. Present members of that group and their organizational affiliations are listed below.

Please direct any comments regarding this guide to the DOE Reliability and Lifetime Working Group at postings@lightingfacts.com.

–  –  –

* NGLIA member †On behalf of the U.S. Department of Energy

LED Luminaire Lifetime Recommendations, June 2011 Page 30

Pages:     | 1 |   ...   | 3 | 4 ||


Similar works:

«Airship, Automaton, and Alchemy: A Steampunk Exploration of Young Adult Science Fiction A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Arts in English by Jou-An Chen University of Canterbury 2012 Table of Contents Acknowledgments Abstract Introduction Chapter One Young Adult Science Fiction How to Build a Steampunk Time Maze Steampunk and Posthumanism Chapter Two The Frankenstein Myth Ecotopia Utopia Revisited Chapter Three Power and the Living Doll The...»

«AIAA 2007-2854 AIAA iInfotech@Aerospace/i 2007 Conference and Exhibit 7 10 May 2007, Rohnert Park, California A General Approach to Terrain Relative Navigation for Planetary Landing Andrew E. Johnson*, Adnan Ansar † and Larry H. Matthies‡ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 Nikolas Trawny §, Anastasios I. Mourikis** and Stergios I. Roumeliotis†† University of Minnesota, Minneapolis, MN 55455 We describe an algorithm for navigation state...»

«OFFICE OF THE TRAFFIC COMMISSIONER (WEST MIDLANDS) APPLICATIONS AND DECISIONS PUBLICATION NUMBER: 2698 PUBLICATION DATE: 20 June 2016 OBJECTION DEADLINE DATE: 11 July 2016 Correspondence should be addressed to: Office of the Traffic Commissioner (West Midlands) Hillcrest House 386 Harehills Lane Leeds LS9 6NF Telephone: 0300 123 9000 Fax: 0113 248 8521 Website: www.gov.uk/traffic-commissioners The public counter at the above office is open from 9.30am to 4pm Monday to Friday The next edition of...»

«Distingo 1.2 Distingo – Terrain in Detail Version 1.2 Contents Overview Prerequisites Use Shader Type Standard PBR or Standard Specular PBR Standard PBR Example Standard Specular PBR Occlusion Shaders Blend Shaders Global Settings Unity Terrain Global Settings Mesh Terrain Global Settings Blend Global Settings Blend Texture Occlusion Texture Blend Power Occlusion Power Texture Channels Standard PBR Texture Channel Splat Normal Occlusion Near UV Multiplier Far UV Multiplier Normal Power...»

«2016 Magic Hat Mardi Gras Call for Floats Packet CALLING ALL REVELERS! Do you think you’ve got what it takes to have a float in the 21st Annual Magic Hat Mardi Gras Parade? It’s an exhilarating ride and it all takes place on Saturday, March 5, 2016. If you want to participate with a float, here’s what you need to do. 1. Read and Sign the Guidelines. There are several changes from year’s past, so please read the entire “Float Participation Guidelines” section of this packet, and sign...»

«WCD Thematic Reviews Social Issues I.2 Sharing Power Dams, Indigenous Peoples and Ethnic Minorities Final Version : November 2000 Prepared for the World Commission on Dams (WCD) by: Marcus Colchester Forest Peoples Programme Secretariat of the World Commission on Dams P.O. Box 16002, Vlaeberg, Cape Town 8018, South Africa Phone: 27 21 426 4000 Fax: 27 21 426 0036. Website: http://www.dams.org E-mail: info@dams.org World Commission on Dams Orange River Development Project, South Africa, Draft,...»

«S:\Common\Cadets\RAF\Current RAF Admin Mar 2014-\CCF Stuff\Ultilearn\20100825-Ultilearn Student Manual-U-Logs4b.Doc 13 March 2012 Ultilearn User Manual Version 3.0 For The Ultilearn Learning System Headquarters Air Cadets Logistics – Bader (Logs 4) Bader Project Number – 001hb.2 Prepared by: Andrew Bracegirdle Bader Developer HQAC RAF Cranwell NG34 8HB 13 March 2012 1 S:\Common\Cadets\RAF\Current RAF Admin Mar 2014-\CCF Stuff\Ultilearn\20100825-Ultilearn Student Manual-U-Logs4b.Doc...»

«Acknowledgements This report has been prepared by the research team and the community participation team at The Children’s Society. We would like to thank all the children, schools and organisations in Nottingham City who participated in the research and consultations which made this report possible. We could also like to acknowledge the support given to this project by Charlotte Malik, Pat Whitby, Carol Frankland, and Linda Abbot from Nottingham City Council. © The Children’s Society,...»

«SOMEWHAT CONTINUITY VIA BIOPERATION-SEMIOPEN SETS K. JHANSI RANI∗1, G. SHANMUGAM†1 and N. RAJESH‡1 1 Arulanandaammal Nagar,Thanjavur-613007,Tamilnadu, India 2 Department of Mathematics, Jeppiaar Engineering College, Chennai-600119,Tamilnadu, India 3 Department of Mathematics,Rajah Serfoji Govt. College, Thanjavur-613005,Tamilnadu, India May 31, 2015 Abstract In this paper, we introduce and study the weak form of [γ, γ ′ ]-[β, β ′ ]-semicontinuous functions called somewhat [γ, γ...»

«Working Paper no. 70 Cities and Fragile States THE OPEN CITY: SOCIAL NETWORKS AND VIOLENCE IN KARACHI Azmat Ali Budhani, Haris Gazdar, Sobia Ahmad Kaker, Hussain Bux Mallah Collective for Social Science Research March 2010 Crisis States Working Papers Series No.2 ISSN 1749-1797 (print) ISSN 1749-1800 (online) Copyright © A.Ali Budhani, H. Gazdar, S. Ahmad Kaker, H. Bux Mallah, 2010 24 Crisis States Research Centre The Open City: Social Networks and Violence in Karachi Azmat Ali Budhani, Haris...»

«New Metrics for Meaningful Evaluation of Informally Structured Speech Retrieval Maria Eskevich1, Walid Magdy2, and Gareth J.F. Jones1,2 1 Centre for Digital Video Processing, School of Computing, Dublin City University, Dublin 9, Ireland 2 Centre for Next Generation Localisation, School of Computing, Dublin City University, Dublin 9, Ireland {meskevich,wmagdy,gjones}@computing.dcu.ie Abstract. Search effectiveness for tasks where the retrieval units are clearly defined documents is...»

«DOCUMENT RESUME FL 024 557 ED 407 871 Mhathuna, Maire Mhic AUTHOR SLA before ABC: Factors Facilitating Second Language TITLE Acquisition in Irish-Medium Playgroups. PUB DATE 95 11p.; For serial publication in which this article appears, NOTE see FL 024 547. Journal Articles (080) Reports Research (143) PUB TYPE TEANGA: The Irish Yearbook of Applied Linguistics; v15 JOURNAL CIT p127-136 1995 EDRS PRICE MF01/PC01 Plus Postage. Child Language; *Classroom Communication; Code Switching DESCRIPTORS...»





 
<<  HOME   |    CONTACTS
2016 www.dissertation.xlibx.info - Dissertations, online materials

Materials of this site are available for review, all rights belong to their respective owners.
If you do not agree with the fact that your material is placed on this site, please, email us, we will within 1-2 business days delete him.