Maintenance Factors & LEDs: Are they being used correctly?
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Transcript of Maintenance Factors & LEDs: Are they being used correctly?
Darryl Bullock,CEng,MSc,BEng(Hons),BA, MILP,MIET
National Project Manager
LED – Maintenance FactorsWhat Is The Correct Solution?
Lighting Design
Choosing the Correct Solution
• Energy
• Design Life
• Colour Temperature
• Optical Performance
Product reliability
As with all Luminaires Conventional or LED, the overall product reliability is determined by the integration of
packaging and assembly of components into a final product, ensuring that each of the component parts are adhered to with respect to drive conditions and thermal
management.
Lumen DepreciationMost LEDs experience a gradual reduction in light
output over the lifetime of operation
Lumen MaintenanceThe reliability of the LED to maintain its light output
during operation As such, any degradation or reduction in performance can be either from a reduction in the light‐emitting efficiency of the LED chip or a reduction in the light transmission of the optical path within the LED
package, module or fixture.
Projected Energy Rise
Design Life• The subject of maintenance factors for LED lanterns that
is a topic is a topic that is being raised on a frequent basis.
• Lumen maintenance is taken from LM80‐08 report. All reputable LED manufacturers produce TM21 data for 10,000 hours of operation of their LEDs at various drive currents and junction temperatures which can be used to extrapolate lumen maintenance at end of life.
• LM80‐08 recommends that the extrapolation period should not exceed 6 times the test period, or 60,000 hours. However this is not helpful when trying to predict 100,000 hours.
Common Denominators• All lanterns are subject to the same MF relating to
cleaning frequency and environmental zone. So for E1/E2 6m column 72 month cleaning frequency this will be 0.92
• After this I think the chosen maintenance factor varies from product to product depending on the information available.
• Is this the case ??• Less pollution
The life of LEDs• The life of LEDs (Lx) is defined as the length of time
during which the LEDs will• provide more than a claimed percentage (x) of the
initial light output.• A manufacturer will declare values for life and lumen
maintenance, usually at a specified ambient temperature.
• The factor Lx takes into account the general decline of light output over life.
• In addition to this there is likely to be a failure of LEDs, comprising both catastrophic (total)
• failure and a steep decline in light output to a value• considered to be below acceptable operation.
Current Vs Light
Lifetime @ 700mA
Lifetime @ 350mA
Controlling Temperature
The failure rate over the rated life is defined
as the failure fraction (Fy) • The failure rate over the rated life is defined as the failure fraction (Fy) where y is the percentage of LEDs that will have failed at the end of rated life. For example, F10 (100000 h) indicates that 10% of the LEDs will no longer be considered operational at 100 000 h.
• For lighting design the failure fraction Fy needs to be taken into account. Using the example, if 10% of the LEDs have failed then 90% will be operational; this is equivalent to a survival factor of 0.9.
L70 @ 35oCAlso known as L70B50 which is the point when 50% of the LED’s lose 30% of their Lumen Output
What Drive Current• For lighting design, the overall maintenance factor for
LED luminaires takes into account the following factors:•• • The lumen maintenance of the LEDs at the end of their
rated life – this is equivalent to lamp lumen maintenance factor (LLMF);
•• • The failure fraction of the LEDs at the end of their rated
life – this is equivalent to lamp survival factor (LSF);•• • The reduction in light output owing to the
accumulation of dirt on the light‐emitting parts of the luminaire (luminaire maintenance factor, LMF) – typical values are shown in Table B.1.
Environmental Zone
Maintenance factors for LED luminairesDerived from using the above formula and the BS5489‐1:2013 BS13201‐3(informative)Maintenance factors for LED luminairesProposed Lantern –Mounting Height 8mMaintenance Factor: Lantern L95/F5 = 50,000hrs – Cleaning Cycle – 0.92 So the total MF for our luminaire = LMF x LLMF x LSF
MF= 0.95*0.95*0.92= 0.83Intensity G4Environment Zone ‐ E3Proposed Lantern Mounting Height 5mMaintenance Factor: Lantern L95/F5 = 50,000hrs – Cleaning Cycle – MF= 0.95*0.95*084 = 0.76Intensity G4Environment Zone ‐ E3
Maintenance factors for CLO LED luminaires(informative)Often our customers are asking for Constant Light Output which means the lumen depreciation is compensated for by increasing the drive current over the life of the product.In this case the MF used should be = LMF x LSF
Maintenance factors for LED luminairesProposed Lantern –Mounting Height 8mMaintenance Factor: Lantern L95/F5 = 50,000hrs – Cleaning Cycle So the total MF for our luminaire = LMF x LSFMF= 0.95*0.92= 0.87Intensity G4Environment Zone ‐ E3
Proposed Lantern Mounting Height 5mMaintenance Factor: Lantern L95/F5 = 50,000hrs – Cleaning Cycle –MF= 0.95*084 = 0.79Intensity G4Environment Zone ‐ E3
NON CLO
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Start NON CLO
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CLO CLO Increase
Choosing the Correct Solution with an
Agreed Common Design Criteria That
Takes Away Any Confusion Lumen Output (LED or Lantern)
Maintenance Factor Calculations
Allowing a Common Approach for Lighting
Engineers To Apply These To Their Designs
Thank You For Your Attention
Any Questions
?