Low voltage electronic transformer Ask questions and find answers to many subjects relating to electrics and electrical work

[iancbs]

I have a string of LV lamps which used to run off a "proper" transformer. This has burnt out and a replacement electronic "transformer" of the same VA only half lights the lamps. Do I have to use an old style transformer (non-electronic) for this?

[collectors]

You would be better off by-passing the old transformer & making the circuit 230 volt & fitting individuals 50/60va tranny's to each light. They are only about a fiver each.

[ericmark]

An extra low voltage transformer has no regulation and gives no real advantage to using low voltage lamps other than the safety feature of having extra low voltage rather than low voltage. Do note low voltage is normal mains voltage the 12 volt used with many lamps is extra low voltage.

The inverters however not only reduce the voltage but also regulate the voltage and supply the lamps with a supply that ensures they give the best light for the longest time. However they not only have a maximum output but also a minimum output and you must ensure the lamps even when some blow are within the range of the inverter.

Because there will be a volt drop in the cable often a transformer is used for each lamp very local to lamp rather than using one large unit to power many.

Also the whole idea is to supply the lights with a controlled voltage so that the tungsten is reflected off the very hot quartz back onto the element so to use any dimmer in circuit defeats the whole point of using an inverter. There are dimmers that will work but there are two types leading and lagging and they need to match the type of inverter but really pointless as that would defeat the whole point of using an inverter.

If it is being used for the 50mm spot lamps then they are not all the same. There are different voltages although 12 volt seems to be normal you can get 6 volt and 24 volt and 48 volt versions plus special 13.8 volt for use in boats direct off there batteries. There are also a range of angles and wattages and it is so easy to replace with wrong type including Dichroic. The Dichroic reflector only reflects light and not heat and is used so as not to overheat the item being illuminated but means behind the lamp gets very hot. The GU10 and GZ10 low voltage lamps are designed so the GZ type "Dichroic" will only fit in a GZ holder but the GU type will fit in both. However with extra low voltage there is no such safety feature and one can fit the wrong type.

In theory the extra low voltage lamps are brighter and last longer than low voltage lamps but in practice it depends on where you live and what the local voltage is and in many cases the low voltage GU10 lamp works better than the extra low voltage type with no need to mess around with transformers or inverters. Only where you have fluctuating voltage does the inverter and extra low voltage lamp work better.