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Shedding more light on LED

By switching CCFL to LED lighting, industry (and mining is not the exception) is not merely subscribing to a fad, but driven by the necessity to increase productivity and safety, writes Eben Ferreira, Engineering Manager of NORDLAND LIGHTING (PTY) LTD.

Just over ten years ago it would have been barely credible to expect LED technology to take the industrial lighting market by a proverbial storm in the years that were to follow. But now, it is becoming a standard in various industries. It is easy to comprehend why industry is adopting LED without a second thought. There are a number of factors behind this phenomenon.

1. Cost savings over time
In the beginning stages, LED technology was available to the user at huge price margins. Now, its initial cost is significantly lower than ever before. In addition, the long-term savings are higher as LED life is considerably greater than other sources. In fact, the savings in energy costs alone will make up the overhead of adopting LED tech within 5 years.

2. Robustness
LED lamps are more robust than normal fluorescents. For instance, if you happen to drop an LED module it will not break apart like glass tube technology. This also means they eliminate the need for special anti-vibration lamp holders for conveyor/high vibration applications. By using LED technology, you are going to save costs in high vibration zones which mines are prone to. Traditional lights fail and break due to their construction and the harsh environment they exist in, whereby LEDs are robust and of a solid-state nature. Vibration does not affect them as adversely as other sources. This attribute is evident in products such as LED bulkheads, Zoned LED fittings, LED Flood lights, LED area lights.

3. Better power correction
There is better power factor correction from LED ballasts with less losses due to copper windings/eddy currents than in traditional magnetic ballasts.

4. Cold temperature and energy efficiency
LEDs can operate at very cold temperatures without the need for special equipment. Furthermore, LED lamps are more energy efficient than traditional sources. LEDs emit most of their input power to light than HID sources. HID sources lose efficiency as they emit lots of energy in the form of heat.

5. 100% lumen output
LEDs operate at 100% output from the moment they are switched on, while traditional sodium lamps need ramp up time in order to operate at their maximum lumen output, which wastes time and energy. Also, LEDs are not prone to lose lifespan if they are switched on and off repeatedly. Above and beyond, LEDs can be directed towards where you want the light to go by using optics. Most importantly, while reflectors in traditional lamps cannot be controlled directionally, LED lamps can.

6. Safety
Series circuit wired LED chains can cause large forward voltages, more especially in 100’s of LEDs chained together. Just to illustrate the hazards this creates, wiring 100 LEDs in series with a forward voltage of 3V per LED, means we need a 300V supply (DC) to power the LEDs. Now if that series chain is broken by, for instance, a LED blowing up, or someone disconnecting the circuit by accident while power is flowing, we sit with a 300V arc of electricity which can be fatal. Thus, it is sensible to utilise products from reputable LED manufacturers as they know about these risks and they would have made provision for safety before supplying to end-users. Moreover, LEDs consumes less power overall, which increases safety and lowers costs.

LED light 2 - CFL Haulage

Demystifying lumen output
Another aspect to be wary about is that some manufacturers will make unverified claims of massive lumen/ watt outputs in their products. It is not uncommon for the end-user to discover belatedly that the lumen/ watt claims are for low mA driven LED solutions. While a LED chip can potentially have 170lm/W, the figures claimed will only be at low mA ratings. So, for example if you drive an LED at a maximum current of 100mA with a forward voltage of 10V, it consumes 1W power and can produce 170lm. While the lumen per watt figure may be correct (170lm/W), it might not suit the application for which it is needed, for instance, for example, floodlighting. Thus, it will be more advantageous to drive a LED at 500mA, 10V forward voltage producing 5W and 600lm (120lm/W). The long and short is that don’t be fooled by manufacturers claiming high lm/w ratings. Rather consult datasheets and determine if the LED chip will do for the application in mind.

Colour temperature
The colour temperature of LED chips have either a positive and negative effect on lumen output. An identical chip with a 6500K temperature will typically produce a higher lumen output than a 4000K one. If we take one LED datasheet of a LED manufacturer, we can see that for an identical LED Chip barring CCT (correlated colour temperature), there are two different lumen outputs claimed. For 3000K at 350mA, the LED in question will typically produce 465lm output. For the same LED at 6500K it is 510lm.

Risk Group Ratings – safety level gauge
An overlooked safety point is when lumen output is at higher CCT Kelvin ratings. RG (Risk Group) ratings of the LED light define how dangerous the LED light output is to your eye and retina. Studies have revealed that the higher the CCT value, the higher risk. To ensure a high level of safety companies must comply with RG ratings. It is advisable to use 4000K modules. It is important to consult with manufacturers about IEC 62471-2006 about their ratings. In a nutshell, the IEC 62471-2006 lists the RG ratings as follows:

  • RG-0 means there is no risk
  • RG-1 means that there is a low risk under normal operation
  • RG-2 means moderate risk. Does not pose a hazard due to aversion response to bright light or thermal discomfort
  • RG-3 means High risk, Hazardous even for momentary exposure

Measuring lifespan
LED Manufacturers will claim 50000hr + lifetimes from their LEDs. These values have all been theoretically achieved because LED technology is evolving so fast that no chip is utilised for that amount of time. These values also differ according to the environment these LEDs operate in. It is important to note that higher ambient temperatures as well as running temperatures can deteriorate lifespan. Hence, always remember to consult the data sheets for the LM-80 ratings. These ratings show the theoretical lifespan of the LED, taking into account factors such as temperature LED light 2 – CFL Haulage and current conditions.

LED light Haulage

There are two norms of measuring the lifespan of an LED, TM-21 and LM-80. LM-80 testing involves burning the LED for 6000hrs, at constant current at 3 set temperatures. The luminous flux is then measured over this time in intervals and the data gathered is correlated.

TM-21 takes the LM-80 data, uses algorithms and statistical approaches to make a prediction of the lifespan of a chip. There are two types of TM-21 testing however, Reported and Calculated. Reported will usually show 6 times the LM-80 hours. So LM-80 of 6000hr will show 36000hr lifespan. Calculated will take the LM-80 data (be it for X amount of hours burned) and apply algorithms to it calculating a lifespan. This calculated value will usually be higher than the Reported value since it is not limited to hours of testing. It is paramount to check the LM-80 or TM-21 ratings of the LED Chips.These will give you the best indication of the correct assumed lifespan of a LED. If a manufacturer cannot supply you with this data, then the LED might not last as long as expected.

The high cost of buying cheap
Beware of buying cheap LED solutions, which, in most cases, are not good quality. They are usually not rated according to Lumen, Wattage, CRI (Colour rendering index) or the lifespan claimed at 50000hr plus. Cheap LED solutions are usually connected in a series circuit to save costs and construction time. Series circuits will fail the entire module, if one LED chip fails, resulting in outages and costs to replace the fitting. And so, it is important to buy LED fittings or chips from recognised and reliable manufacturers or suppliers. While they are more expensive than some imports from China, in the long term, they serve your needs better. When it comes to LED technology you get what you pay for.

NORDLAND LIGHTING (PTY) LTD offers clients a number of solutions. It retrofits traditional fittings with quality LED fittings. In addition, the company offers zone 2 LED solutions for external environments, as well as conveyor lighting, flood lighting, general area lighting, low, high bay and indoor applications in LED technology.

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