Wednesday, February 15, 2012

Why do we need transformers for low voltage lighting?

Why can't standard 240 volt lamps be used as they use the same amount of power?Why do we need transformers for low voltage lighting?The filaments for low-voltage lights have shorter and thicker filaments so the lights can stand more mechanical shock and vibration. The more compact filaments also make these light sources to be more pointlike and to be focused into a tighter beam than longer filaments would allow. This is advantageous in track lighting and low-voltage spotlights.



The lower voltage of these lights also presents much less of a shock hazard if the lamp housings are damaged, as is likely to happen along footpaths. These housings are also within easy reach of small children and pets, so the absence of dangerous voltages is of special importance in this application. The low voltage is also an advantage in track lighting because the wiring need not be so elaborately insulated to keep everything safe.Why do we need transformers for low voltage lighting?
240 volt lamps are designed to be bright only at their rated voltage. At 12 volts or so they will just glow dimly because their high resistance needs high voltage to get them bright.Why do we need transformers for low voltage lighting?Low voltage lighting is not about power saving, you are correct in pointing out that the same power rating bulb of the same technology (comparing incandescent to incandescent, that is) will give the same light. It is about safety rating. 24 volt or lower systems are essentially incapable of delivering a lethal electrical shock, so can be used in exposed, in-pool, or direct burial outdoor systems that would be unsafe and violate construction codes with higher source voltages.Why do we need transformers for low voltage lighting?
ohms law.



the lamp will be rated at 50w say at a stated voltage 230V.



for this to happen the lamp will have a resistance which is fixed.



if you only give the same lamp 12 v then it will not be very bright. P=V.I : since i=v/r then P=V 2/rWhy do we need transformers for low voltage lighting?Low voltage lighting utilizes normally 12 V, the transformer is needed to convert the 120 V down to the 12 V so that the lights will run at the required level. They do consume less power and you can load more on the same circuit.







- It is true that you can use this cable outside, but most outdoor fixtures are still 120 V, and you can use NMWU as a direct burial wire. There are few fixtures that are sold that utilize low voltage, I would say at least 3/4 of the fixtures being sold are line voltage.Why do we need transformers for low voltage lighting?
The two most significant reasons for using low voltage wiring for out door lights are safety and convenience.



Safety -- Low voltage systems are safe because human skin has sufficient resistance to ensure a person cannot receive a lethal shock from a 12 volt system.



convenience -- Because of safety issues permits and inspections are required if installing 120 VAC outdoor lights.

In most places there are no such requirements for 12 V systems.
Low voltage lighting is used where the higher 'line` voltage would be a hazard.

It would be possible to make basically the same lamps with filaments sized for a higher voltage, but the fixtures and tracks would become far too bulky and expensive if they were designed to be safe to handle when wired for the higher voltage.

Many Codes require special protection, (GFCIs). for high voltage fixtures in the applications that are the domain of 12V. lighting, and some will not permit the higher voltage to be used for that application regardless of protection.

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