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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]
CONFIDENTIAL - Cree Proprietary
What Could Go Wrong?
A lot can go wrong here…. And in your LED program if you don’t properly consider Reliability Issues
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
A “Normal” Vibration Application
City of Greensburg, KS – Greensburg, KS
System Reliability for Outdoor SSL
CONFIDENTIAL - Cree Proprietary
A “Typical” Bridge Vibration Application
I35W, St Anthony Falls Bridge – Minneapolis, MN
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
Relevant Testing and Standards - IEEE/ANSI C62.41.2
How much protection is needed? Does everyone require the same level of protection?
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
IEEE/ANSI C62.41.2 • Variables to Consider (continued):
Power system characteristics Interactions with communication and other systems
CONFIDENTIAL - Cree Proprietary
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)
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
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)
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
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
CONFIDENTIAL - Cree Proprietary
What Could Go Wrong?
Remember…much can go wrong if you don’t consider Reliability Issues and Specify based upon the Standards