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Multiload LED Powerplant

Issue 61 Jun / Jul 2011

Multiload react to the need for stabilising power supplies for LED cable runs with the LED Powerplant in both 12V and 24V versions. David Morgan puts it through its paces.

Multiload, the London based power supply manufacturer, was established by Brian Cuthbertson back in the heady days when low voltage halogen lamps were still a fairly new and exciting technology. At that time the lighting industry struggled to deal with high current, low voltage wiring problems and voltage drop in particular with remote transformer installations. 

The Voltmaster system, Multiload’s first product, overcame a variety of problems with existing transformers by monitoring and controlling the voltage which is actually delivered to the halogen lamp, via a feedback loop with separate sensor wires, to maintain a constant 11.8 volts even on very long cable runs. This voltage stabilisation combined with a patented soft-start system ensures maximum light output and extends lamp life dramatically, in many cases up to four times the rated life.

While sales of the Voltmaster continue in those areas of the specification market where low voltage halogen is still the preferred light source, Multiload has recognised that the future will be more about LEDs than halogen. The company has therefore turned its design and development attention to powering LEDs and how it can use the ideas and intelligence built into the Voltmaster to provide better solutions for LEDs. 

The result of this development process is the Multiload LED Powerplant which is a stabilised DC power source available in 12 volt 120 watt and 24 volt 240 watt versions. The transformer incorporated in the Powerplant is a large double wound traditional magnetic type providing a true SELV source for use in pools and other applications where this is required. 

The overall build quality and attention to detail in the Powerplant is impressive with four large 4 sqmm terminal connections which are individually fused. This equipment is built to last and if the long life and very low failure rate of the Voltmaster is repeated in the Powerplant then it will be the LEDs that need replacing before the Powerplant.
The development programme for the Powerplant was undertaken in-house at Multiload by electronics specialist Peter Davey and design director David Fitter over a 24 month period.

One of the essential differences between running a halogen lamp and an LED source is that LEDs need constant current rather than constant voltage supply so it might appear that the market for the LED Powerplant would be rather limited. However, one of the most popular formats for miniature linear lighting is LED tape which incorporates resistors to provide the current load from a constant voltage source. This has proved to be a fertile market for the LED Powerplant as typical installations of LED tape, such as miniature cove lighting, detail feature lighting or panel edge lighting, tend to require a remote power source. Using a conventional switch mode, constant voltage LED supply to run remote strips will almost certainly mean that the strips are running below their specified voltage due to losses in the cable run. The LED Powerplant can compensate for a drop of up to 3 volts in the 12 volt version and 6 volts in the 24 volt version. With 4 sqmm cable, the 24 volt LED Powerplant can run strips at the correct voltage from an impressive distance of up to 50 metres.

LED tape is an inherently inefficient LED format with some of the power being turned into heat in the resistors instead of light in the LEDs. Therefore the overall efficiency of a system based on LED tape combined with the LED Powerplant is likely to be lower than a system with a constant current driver running LED emitters directly. However, these drivers would need to be located close to the strip which, in many projects, is not possible due to size limitations. The same logic will apply to any project where it is desirable to use a remote power supply due to lack of space, need for true SELV or for ease of servicing the power supply during the life of the equipment.    

Other ideal applications for the LED Powerplant include outdoor lighting with long cable runs and pool lighting where a true SELV supply is needed and typical LED switch mode DC power supplies would not provide a high enough level of safety protection and cannot be used. Multiload has a proven history of use with the Voltmaster in pool projects including Wild Wadi Aqua Park Dubai.

When used to run a series of LED downlights the Powerplant would ideally be used in conjunction with DC to DC constant current drivers for each LED array to achieve acceptable efficiency. But the advantage of being able to use a single high power supply a long distance from the downlights would still apply.

Dimming LED tape with the LED Powerplant works surprisingly well. All LEDs have a threshold voltage below which they will not operate and this voltage varies from LED to LED. This is why most dimming systems use current control or PWM or a mixture of both. It seems likely that the smooth and reliable dimming with the Powerplant is due to the restistive load built into LED tape. I would assume that other dimming techniques would be needed for luminaires which incorporate DC to DC drivers being powered from a remote Powerplant. The reaction from the lighting design community and luminaire manufacturers to the Powerplant is reported to be positive and it seems likely that the unique features of the product will secure it a strong position in its area of the market for many years to come.

David Morgan runs David Morgan Associates, a London-based international design consultancy specialising in luminaire design and development.
Tel: +44 20 8340 4009
© David Morgan Associates 2011
The views expressed in this article are entirely those of David Morgan and not necessarily those of mondo*arc.


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