Zhaga Making LED Light Sources Interchangeable Progress toward LED standardization is here. If you traveled to Light + Building in Frankfurt this April or Lightfair in May, you may have been pleasantly surprised by the great progress toward LED luminaires with serviceable and commercially available light sources. This is in large thanks to the efforts of the member companies of the Zhaga Consortium, such as Philips, Osram/Sylvania, GE, Samsung, LG and others. This lighting industry group formed just two years ago to establish such standards, and is now announcing the first fruits of its efforts. This white paper explains why such standards are necessary. Today, LED lighting products offering more than100 lumens per Watt (LPW) are not uncommon and provide very efficient energy use compared to traditional light sources. These LED products are showing up in all types of form factors with some fitting into traditional sockets and some using custom interfaces. A visit to Lightfair makes it clear that just about every company is now offering LED products with ever increasing light output and efficiency. One major hurdle that remains today is achieving optimized LED Lighting performance in a product that is convenient for the building occupant to replace. FAQ #1: But LEDs last forever, why do we even care about enduser replacement? The answer is that most LEDs last a very long time, but not all of them, so they must be replaceable. Many early LED luminaires were designed with the LEDs permanently affixed to the luminaire to maximize light output and thermal efficiency. This was considered acceptable because LEDs can last 50,000 hours and longer. LEDs are indeed capable of long service lives, but like all electronic products, they still have infant mortality rates and are susceptible to damage from broom handles, forklifts, and water leaks. They need to be replaceable by the building occupant if efficient LED technology is to succeed in broad applications. Also, when more efficient Light Engines become available, does it make sense to swap lamps or replace entire luminaires? The DoE s Designer Roundtable on the subject cited replacement parts and lack of modularity as major drawbacks to LED adoption. NEMA recognized this in its 2009 white paper, LSD 44 Solid State Lighting The Need for a New Generation of Sockets & Interconnects : Currently, in many LED fixtures, the LEDs are considered "permanent" and cannot readily be replaced in the field by end users or field service personnel. Some LED fixtures treat the LEDs as parts of sub-modules that could be replaced, but are not necessarily constructed in a manner for a simple swap without major disassembly of the fixture. Growing experience with LEDs shows that failures do occur FAQ #2: If LEDs are so efficient, why is thermal management important? It does seem contradictory that a high efficiency product needs its heat output well managed. Actually, LED products produce much less heat than traditional light sources. The difference is that the heat produced in an LED product is highly concentrated at the LED itself and thus creates a very small area of high temperature. The LEDs have a Critical Temperature at which
their life will be greatly affected. Good luminaire design requires a product that reliably stays below this temperature and yet maximizes light output. Traditional lamps with Edison bases, or CFL pin-bases, etc. were not designed to help conduct heat away from an LED inside a lamp. Consequently, LED light sources that use these traditional interfaces have to sacrifice either lamp life or lumen output. NEMA recognized this in the same white paper: The use of existing sockets compromises the capability of solid state lighting. Existing sockets are sub-optimal mechanical and optical configurations. Existing sockets do not provide an adequate thermal path. So, LED product development for general illumination initially followed two different paths: 1) using traditional lamp bases for easy replacement and 2) using integrated luminaires for great performance. As already mentioned, the first addresses the replacement market well, but is limited to products that cannot properly manage heat and thus will sacrifice product life, lumen output, or both. The second option provides the very best performance, but makes field replacement more challenging. Then came LED Modules. Modules allowed easy replacement and also were designed to provide a good thermal conduction path away from the LEDs. These seemed to bridge the missing gap, but then market acceptance was slowed since each was a proprietary system, with a unique size and mounting. This brings us to March of 2010, when a group of lighting-related manufacturers from around the world first met to form the Zhaga Consortium. Zhaga is an industry-wide cooperation aimed at the development of standard specifications for the interfaces of LED light engines. The goal of the group is to enable interchangeability between products made by different manufacturers. As the Zhaga website states: Interchangeability is achieved by defining interfaces for a variety of application-specific light engines. Zhaga standards will cover the physical dimensions, as well as the photometric, electrical and thermal behavior of LED light engines. Zhaga is established for the benefit of the consumers and professional buyers of light engines and luminaires, in the expectation that standardization will prevent market fragmentation into incompatible products. Zhaga standards will increase the confidence to specify and purchase LED products that will be easily replaceable and commercially available, while continuously enjoying the performance upgrades that LED technology enables. In addition, this will foster innovation and competition in the application of LED lighting in general. Zhaga is addressing these concerns through the development of specifications for standardized and replaceable LED light sources that are being incorporated into products of member companies. The 180+ Zhaga members from around the globe are luminaire manufacturers, light source OEMs, component suppliers, and test labs, all committed to address the need of robust and interchangeable LED Light sources. Zhaga promotes the interchangeability of LED light sources for general lighting applications by specifying the interfaces to which manufacturers will conform. These standardized interfaces will enable confident specification of LED luminaires that will have commercially available futureproof light engines, modules, and control gear which can be upgraded as components fail, building occupant needs change, or product efficiencies increase.
Zhaga is defining four such interfaces to assure that the standards are robust: mechanical, electrical, thermal, and photometric (see image below). The mechanical interface addresses matters such as fit with the heat sink, reflector or other optical components, as well as the dimensions of the socketable fit system (if a socket is employed). The electrical interface specifies variables such as input power requirements, connection type, and control capability. NEMA is the lead organization that is developing dimming standards for LEDs; Zhaga has formed a task force to work closely with NEMA on forward phase dimming. The thermal interface, which is a special consideration for LEDs, defines the thermal resistance, heat dissipation, and thermal fit to the heatsink to ensure long life and light output. The photometric interface defines lumen output, color, light distribution. Courtesy www.zhagastandard.org
During these first two years, the Zhaga companies have met a staggering fifteen times to propose, compare, integrate, prototype, and test standardized formats for various lighting applications. The first standard for a socketable downlight engine was approved in February 2011, just 1 year after the initiation of Zhaga. You can see the commercial product that is available below. DOWNLIGHT WITH LIGHT ENGINE & HOLDER LIGHT ENGINE & HOLDER (Luminaire Courtesy of Pathway the Lighting Source) (Philips) (IDEAL) The second approved Zhaga standard was developed for spot lighting. This is a non-socketed LED module with remote located control gear (driver). Many companies again contributed to the development of these products as can be seen in the prototypes below.
Other Zhaga standards completed in the second year were designed around applications for spot lighting, down lighting, and street lighting and can be seen in the images below for basic formats. Other standards for indoor troffer-type and drivers are well underway. Conformance to the robust Zhaga standards is being certified by third party independent labs. In the last few weeks, the first test labs have been authorized. Once a product has successfully passed the third party testing, the Zhaga logo (see below) can be used on that product. The logo is the assurance that the product is in conformance with the standard and is compatible with all other Zhaga certified products for that category. Zhaga provides interchangability standards. These products will still be required to be tested to new or existing UL standards to assure safety and must be cognizant of AHJs to meet the NEC or CEC. More than 25 members showed their Zhaga products at L+B and a similar number are expected to do the same at Lightfair. The member booths are proudly displaying their light engines, modules, control gear, and holders that mate together reliably. But in the end, the market place will determine if these new standard interfaces for LED Lighting will succeed.
Ben Swedberg is the Business Unit Manager for Engineered Solutions at IDEAL INDUSTRIES, INC. and continues to actively participate at Zhaga meetings. IDEAL has been a trusted manufacturer of electrical products for nearly 100 years and is pleased to be participating within Zhaga to assure the successful transition toward LED Lighting in North America. For more information or to be included in our Zhaga update emails, please contact Ben at ben.swedberg@idealindustries.com For more information: www.idealindustries.com/products/oem www.zhagastandard.org Common Terms: As many of the terms used in LED lighting are not the same as those to define traditional light sources, some descriptions are provided here. Control Gear (commonly known as driver): Acting somewhat like a ballast in fluorescent lighting, the Control Gear is made up of electronics that convert input power into the necessary power to drive the LEDs often converting line voltage to lower voltage DC with either constant current or voltage output. The Control Gear also protects LEDs from spikes and fluctuations from the input power. Heat Sink: The part of the luminaire that conducts the heat away from the LED. Light Engine (LLE): The LED module and Control Gear taken as a whole. This might be an integrated assembly comprised of LED module and Control Gear in the same housing, somewhat analogous to a self-ballasted CFL lamp. It could also be a module and Control Gear in different locations within the luminaire connected by a cable, similar to linear fluorescent lamps with ballasts. LED Module (also known as an array): An assembly of LED dies on a printed circuit board, with means to connect electrically, mechanically, and thermally to the LED luminaire.