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12V transformer

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mik60ish | 08:54 Thu 19th May 2005 | Home & Garden
6 Answers
I have just purchased some 12v halogen downlights with no wiring insructions. The transformer is maked L&N on the end with the 2 connections but none on the other end with the 3 connections
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What colour are the three wires?
Question Author
There are no colours just the three connectors marked Sec 11.4V- 0.75 0.75 0.75 to pick up the two white wires going to 12V halogen bulb
I hope someone else can help you, because I do not understand why the transformer should be like that.
On second thoughts it may be that the transformer has three output connections because it can be used to supply two differnt voltages (not at the same time). Obvioulsy one is 11.4v but my problem remains that I would then expect one of the others to be makred with a lower voltage, and the third to be the neutral connection.
Another point I fail to understand is why the imput is marked L and N. It makes no differnce which way round it is connected.
Not convinced that Didwot answer fully explains it.  Try this.  The three outputs on the secondary side of the transformer are likely to be the two ends of the tapping and a centre tap.  This should give 11.4V between each of the ends and the centre.  Try measuring the output between terminal 1 and 2, and then try between 2 and 3 with an AC voltmeter.  If I am right you will get about 15V AC in each case (because the transformer is under no load conditions).  You will also get about 30V if you measure between terminal 1 and 3. Do this and report back, because I am not sure you have a transformer adequate for the job. The 0.75 comments almost certainly refer to the current capacity of the transformer - 0.75Amps maximum.  So you may have a 24V 0.75A transformer with a centre tapping.  If so, this is capable of driving one 20W halogen bulb. How many bulbs are you hoping to drive, and are they 20W or 50W types?
Question Author
Many thanks for your replies, I did ask a friendly electrician.  Who put me right, all 10 of the lights are up and running once again many thanks

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