Newsgroups: sci.electronics.misc Subject: Re: Transformers in parallel and xmas light controllers References: <[email protected]> [email protected] writes: > I am seeking help on 2 topics relating to Christmas fairy lights. > > 1. Transformers in parallel. > The xmas lights run off 240v-24v AC transformers (I'm in Australia). I > have a long run from the transformers to multiple sets of lights so I > want to connect up the outputs of lots of transformers in parallel, then > run a single thick cable, then branch off to the individual sets of > lights. I can ensure that all transformers are in phase, but I am > concerned about what happens if some are slightly higher voltage than > others. Will the higher voltage ones "push" the current in reverse > through the lower voltage ones and burn them out? That's possible in extreme case. In any case the load with many parallel transformers will not load evenly if they are not exactly similar (output somewhat different voltages). If the load does not split even to all tranformers, some of them can overheat. One transformer fails o overheating -> all other fail also. The tolerances for tranformer for such cheap application might be quite high (the bulbs will work even thoiugh the voltage is nit exactly 24V). > One solution I thought of was to connect each to a bridge rectifier, > giving half-wave output, then connect all the outputs together, thus > isolating each from the other. But that is lots of diodes to connect up. That's also an optin. No danger of the reverse-pushing to other transformers. This is complicated and does not guarantee evely loaded outputs. > Do I need to worry, or is there a simpler method of isolating them? There ate no simple and ideal circuit for paralling many cheap transformers. The best approach would be to throw out those low power transformers and use one higher current 24V tranformer to power all the lights. > Please reply to: polsen at ar.com.au (You know what I mean. I don't > want to insert the @ and invite spam.) -- Tomi Engdahl (http://www.iki.fi/then/) Take a look at my electronics web links and documents at http://www.epanorama.net/
