The following CALiPER reports provide a detailed investigation of LED PAR38 lamp performance, covering basic performance characteristics as well as subjective evaluation of beam, shadow, and color quality. Further analysis is provided on flicker, dimming, and power quality characteristics; stress testing; lumen and chromaticity maintenance; and chromaticity shift modes. These reports are intended to educate the industry on market trends, potential issues, and important areas for improvement.
Application Summary Report 20: LED PAR38 Lamps
An initial sample of 38 LED PAR38 lamps and 5 halogen and CFL benchmarks underwent photometric testing according to IES LM-79-08. CALiPER Application Summary Report 20, which also includes an addendum covering 6 additional LED products and 3 additional benchmarks that were similarly tested, focuses on the basic performance characteristics of the LED lamps compared to the benchmarks, as well as performance relative to manufacturers' claims. (34 pages, November 2012—Addendum September 2013).
Following the initial CALiPER report on LED PAR38 lamps, several additional special investigations were initiated. The results of these investigations are divided into four reports, each of which includes new data for all or a subset of the products described in Application Summary Report 20. Information on basic performance characteristics—such as efficacy, lumen output, and beam angle—is generally not repeated in any of the special investigation reports.
Report 20.1: Subjective Evaluation of Beam Quality, Shadow Quality, and Color Quality for LED PAR38 Lamps
This report focuses on human-evaluated characteristics, including beam quality, shadow quality, and color quality. Using a questionnaire that included rank-ordering, opinions on 27 of the Report 20 PAR38 lamps were gathered during a demonstration event for members of the local Illuminating Engineering Society (IES) chapter. This was not a rigorous scientific experiment, and the data should not be extrapolated beyond the scope of the demonstration. The results suggest that many of the LED products compared favorably to halogen PAR38 benchmarks in all attributes considered. LED lamps using a single-emitter design were generally preferred for their beam quality and shadow quality, and the IES members' ranking of color quality did not always match the rank according to the color rendering index (CRI). (31 pages, October 2013)
Report 20.2: Dimming, Flicker, and Power Quality Characteristics of LED PAR38 Lamps
This report focuses on the flicker and power quality performance of the Series 20 lamps at full output and various dimmed levels. All of the Series 20 PAR38 lamps that manufacturers claimed to be dimmable (including all halogen lamps) were evaluated individually (one lamp at a time) both on a switch and under the control of a phase-cut dimmer designed for use with "all classes of bulbs." Measurements of luminous flux, flicker, and power quality were taken at 10 target dimmed settings and compared with operation on a switch. Because only a single unit of each product was evaluated on a single dimmer that may or may not have been recommended by its manufacturer, this report focuses on the performance of the products relative to each other, rather than the best-case performance of each lamp or variation in performance delivered from each lamp. Despite these limitations, the results suggest that LED performance is improving, and performance trends are beginning to emerge, perhaps due in part to the identification of preferred LED driver strategies for lamp products. (32 pages, March 2014)
Report 20.3: Stress Testing of LED PAR38 Lamps
A small sample of each of the Application Summary Report 20 PAR38 lamp types underwent stress testing that included substantial temperature and humidity changes, electrical variation, and vibration. The results do not directly address expected lifetime, but can be compared with one another, as well as with benchmark conventional products, to assess the relative robustness of the product designs. (24 pages, December 2014)
Report 20.4: Lumen and Chromaticity Maintenance of LED PAR38 Lamps
This report focuses on lumen maintenance, chromaticity maintenance, and catastrophic failure in 32 of the Series 20 LED PAR38 lamps and 8 benchmark lamps, which were monitored for nearly 14,000 hours at ambient temperatures between 44°C and 45°C. (66 pages, December 2014)
Report 20.5: Chromaticity Shift Modes of LED PAR38 Lamps Operated in Steady-State Conditions
This report builds on CALiPER Report 20.4, focusing on the same 32 PAR38 lamps but investigating causes of color shift and parametric failures. It provides a tear-down analysis of the lamp models and performs additional analyses on the spectroradiometric data obtained using a specially developed automated long-term test apparatus. (76 pages, February 2016)