system reliability for outdoor ssl -...

CONFIDENTIAL - Cree Proprietary

System Reliability for Outdoor SSL



CONTACT INFORMATION: Tom Bevan

Business Development Manager – Roadway/Utility/Municipal

Cree / BetaLED 1200 92nd Street, Sturtevant, WI 53177 262.884.3207 [email protected]


Luminaire System Life There’s more to Life than L70.


Luminaire System Life What about Mechanical Design?


Luminaire System Life

What about Product Durability?


What Could Go Wrong?

A lot can go wrong here…. And in your LED program if you don’t properly consider Reliability Issues


Non-Illumination Related Reliability Concerns • Mechanical

Vibration LED’s

• Electrical Driver Life and Reliability Surge Protection

• Exterior Finish Corrosion Protection

With Focus on Generally Accepted Standards


Vibration


A “Normal” Vibration Application

City of Greensburg, KS – Greensburg, KS



A “Typical” Bridge Vibration Application

I35W, St Anthony Falls Bridge – Minneapolis, MN


A “California” Bridge Application Maxwell Street Bridge – Napa, CA


Types of Roadway Vibration • Wind Induced (ground mounted) • Traffic Induced (bridge / overpass mounted)

Relevant Testing and Standards • ANSI C136.31-2001 Normal Applications Vibration Standards • ANSI C136.31-2001 Bridge & Overpass Vibration Standards • CALTrans 611 Vibration Testing


ANSI C136.31-2001 & CALTrans 611 Vibration Testing

These standards were designed to simulate what could be encountered In normal installations and are not intended to cover natural / catastrophic disasters


ANSI C136.31-2001

Some of the Details • Special vibration tables are required • Mount accelerometer @ luminaire center of gravity • Test to the levels per Tables 1 and 2 (next two slides) in the x, y and z planes • Luminaire shall be capable of withstanding the described vibration for 100,000 cycles in

each plane • A major change in frequency or displacement indicates failure • And, there should be no damage to, loosening of any part of the luminaire or any

changes that could result in a safety problem


ANSI C136.31-2001 Normal Applications


ANSI C136.31-2001 Bridge & Overpass Applications


CALTrans 611 Vibration Testing These test guidelines may be negotiated by the specifier

CALTrans 611 Vibration Testing Requirements

Horizontal Cyclic Loading Test (critical in ground-mounted luminaires) • Adjust frequency and displacement until 1.5 G peak to peak (0.75 G peak)

acceleration is obtained • Driver is installed for this test • Cycle until 2 million cycles or until failure occurs


CALTrans 611 Vibration Testing Requirements Vertical Cyclic Loading Test (critical for bridge-mounted luminaires) • Adjust frequency and displacement until 3 G peak to peak (1.5 G peak)

acceleration is obtained • Driver is removed for this test • Frequency must be kept under resonant frequency for this test • Cycle until 2 million cycles or until failure occurs

CALTrans 611 Vibration Testing


LED Mechanical Life


LED Mechanical Failure Rates

LED Possible Failure Modes Chip / Package

•Cracking •Broken or loose elements

System •Driver •Assembly related

Shipping and Handling These are reasons why an LED may stop working, however the LED itself is very mechanically reliable


LED Mechanical Failure Rates

LEDs are Extremely Reliable What are the odds of 3 or more LED failing in a 50 LED luminaire?

Probability at 10,000 Hours = 1 in 1.25E-10 Probability at 25,000 Hours = 1 in 1.95E-9 Probability at 50,000 Hours = 1 in 1.56E-8 (1 in 156 Million) Probability at 100,000 Hours = 1 in 1.25E-7


Driver Life and Reliability


• Reputable Manufacturers

• Warranty


Surge Protection


Relevant Testing and Standards - IEEE/ANSI C62.41.2

How much protection is needed? Does everyone require the same level of protection?


IEEE/ANSI C62.41.2™-2002 • This is a recommended practice for low voltage (≤1000VAC) circuits

• No performance requirements are specified • There are many variables to consider in this complex subject area • They are:

Protection level desired Worst case or typical case scenarios No system damage No upset Specific equipment sensitivities


IEEE/ANSI C62.41.2 • Variables to Consider (continued):

Power system characteristics Interactions with communication and other systems


IEEE/ANSI C62.41.2 Two Major Types of Surges for equipment connected to low

voltage AC power circuits • Voltage Surges • Current Surges

Two Major Sources

• Lightning • Switching Surges (power system)


IEEE/ANSI C62.41.2

Lightning Surges: The standard points toward two cases / scenarios: • Scenario 1: Indirect Lightning Flash – the most common type

• Scenario 2: Direct Lightning Flash – the least common

It further defines Location Categories within Scenario 1 • Categories A, B and C • These categories relate to service connection location and the distance to the installation


IEEE/ANSI C62.41.2

•Different types of surge test wave forms are described for standard and special environments / difficult applications •Peak voltages, peak currents, frequency and test duration are also factors defined in recommended test methods

•The MSSLC Model Specification includes an Electrical Immunity Appendix D, that recommends three appropriate test specifications and related procedures for LED Roadway Luminaires

•Test 1: Ring Wave •Test 2: Combination Wave •Test 3: Electrical Fast Test (EFT)

•Please refer to the MSSLC Model Specification for details


Exterior Finish



• Aesthetic Concerns

• Mechanical Concerns


Salt Spray (Fog) Test Relevant Testing and Standard – ASTM B117

• This practice provides a controlled corrosive environment which has been

used to produce relative corrosion resistance information for specimens of metals and coated metals in a given test chamber

• Special Salt Solutions, Air Supply, Salt Fog Chamber, Specimen Cleaning etc.

• Test specimens: A scratch or scribed line is made through the coating with a sharp instrument (per ASTM D 1654) so as to expose the underlying metal

• Results reported based upon creepage from scribe in millimeters (per ASTM D 1654)


Salt Spray (Fog) Test Results Per ASTM D 1654


Corrosion and UV Resistance

Relevant Testing and Standard ASTM B117 Elevated Ambient Salt Fog (Pass at 2,000, 3,000, 4,000, 5,000 hours?)

Salt Spray (Fog) Test Results Per ASTM D 1654


Non-Illumination Related Reliability Concerns • Mechanical

Vibration LED’s

• Electrical Driver Life and Reliability Surge Protection

• Exterior Finish Corrosion Protection

With Focus on Generally Accepted Standards


How to Predict Reliability?

Look to standards


How to Specify Reliability?

Look to standards


What Could Go Wrong?

Remember…much can go wrong if you don’t consider Reliability Issues and Specify based upon the Standards


Thank You

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