Wednesday, December 18, 2013

Is AC or DC LED lighting technology more suitable? The considerations and impacts!

Based on The Sunday Times dated 15 December 2013, we are equally excited and happy to see the article on LED technology being given the airtime.

LED there be light; Author: Christopher Tan

Items of particular interest to us that was mentioned;
1. Harmonic current contamination of the power grid
2. Electromagnetic interference
3. Narrow light distribution
4. Harmonic distortion may result in melted wires and transformers breaking down for a building replacing 10000 LED light tubes.

From the above, kindly allow us to discuss our thoughts on harmonic distortion;

Harmonic distortion is the change in the waveform from the supply voltage from the ideal sinusoidal waveform. Harmonic distortion is a concern mainly because AC LEDs is intended to be used instead of the standard DC LEDs available in the market.

One key reason for using either AC or DC for LED lighting stems from the distance where the light needs to be laid. DC suffers power losses over long distances and require devices (e.g. amplifiers) to maintain the voltage.

Secondly, it may result in a better utilisation of power since there is no need for AC-DC converter /power supply / transformers to convert AC to DC.

Also, using AC LED may not require much re-wiring for existing infrastructure. It would make it easier for installation.

Is AC a much better solution than DC led lighting for buildings then?

1. The installation of DC led lighting might prove to be more cost effective for new buildings and infrastructure. The current price for DC powered LEDs is 3-4 times lower than the AC LEDs due to availability and stability. For new buildings without previous electrical connections, direct 230v power cable can be supplied to the lighting point for the DC lighting device which comes with the driver. The 230v input will not be altered in supply, since it will be rectified by either the external or internal driver of the LED lighting device. It would be a plug and play process, thus reducing even further the man hour required for installation.

2. There might be some losses due to the power factor of the driver. However, do note that DC led like AC led has a lower power requirement compared to fluorescent. Does a 10%-15% (1w-1.5w) reduction of a 12w DC LED justify the need to use a 12w AC LED lamp? Converting to kwH might not make much economic and environmental sense.

3. LEDs available in the market is primarily DC driven at the moment. The economies of scale has lead to the lower cost structure. The key consideration here is to use reliable and good LED drivers. Check with your vendor for their track records, brand of LED drivers and test report if possible.

4. Existing buildings, commercial units owners need not frown. After all, re-wiring to bypass existing ballast should not cost above $15.00 per tube. Our internal break-even analysis on the cost of a 4ft LED tube and installation shows a reasonable break even period of 6 months to 1.5 years, depending on hours used.

5. A main benefit of using AC LEDs is to minimise re-wiring works for existing fixtures. However, the present of an existing magnetic ballast (Power Factor ranges from 0.5 - 0.8) in the electrical circuit will also not give you the efficiency and electrical cost savings from using LEDs. Hence, if re-wiring is going to be done in any case, it might be easier to use DC LEDs. By simplifying the electrical connection, more is achieved with less.

You might want to refer to the articles below for more information.


Disclaimer: Kindly note that the opinions and personal thoughts stated above are purely based on our own internal research and assessment on the topic of harmonic distortion for LEDs. It should not be deemed to be an official research paper or to be used for any other purposes apart from your reading pleasure. We will not be liable for any implication arising from the use of our information presented here.


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  3. I think the best lighting is LED lgihting fahrrad lampe!