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Adding SELV lighting transformers in parallel ?

Discussion in 'Electrics UK' started by maycat, 17 Dec 2018.

  1. maycat

    maycat

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    I've got a 12V tension wire lighting run that's been in place for a number of years and works fine, running off an electronic transformer (I know that's problematic, but it was done before I moved in ...).

    I'd like to add a LED tape run off the same lighting circuit as a fill-in. I did a little experiment with bits I had in, chaining in parallel an LED driver off the 240V feed into the existing transformer, but whilst the LED tape worked fine, the original transformer started buzzing and the attached lights flickering.

    So any idea what I did wrong, and how should you run multiple 12V transformers off a single circuit ?

    Thanks.
     
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  3. Taylortwocities

    Taylortwocities

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    You can only connect the two supply devices on the 230volts (mains)side.
    If that is what you did, that should work.

    The outputs will be completely different and you would stand a chance of killing one or both if you paralleled them up.
     
  4. bernardgreen

    bernardgreen

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    A tension wire system can be supplied by an SMPS provided that the SMPS has been designed and built with the necessary filtering on the output to remove the radio frequency energy created in the device. Some SMPS devices are designed with the filtering in place but when built the filter components are not fitted to the PCB. ( cost saving )

    In theory as Taylor said connecting the 230 AC inputs of SMPS devices in parallel to a single supply should work without problems.

    That said if one of the SMPS devices takes power from the mains in a way that creates transient voltages (spikes or dips) or high frequency noise on the mains voltage then these transients or noise might adversely affect the operation of the other SMPS device resulting in a fluctuating voltage on the output.
     
  5. 333rocky333

    333rocky333

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    Are you sure its an Electronic transformer, most tension wire systems come with Torroidal transformers
     
  6. maycat

    maycat

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    Yep, that's exactly what I did - seemed obvious. Both sets of lights "work" - in the sense that they illuminate - but the tension wire is unusable (flickering) and I doubt it is doing much good for the longevity of the first transformer.
     
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  8. maycat

    maycat

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    Yep, it does look like the two transformers are interfering on the mains side, regardless of what RFI they might also be chucking out.

    Bugger. This ought to have been a simple job. Now it looks like I need a pair of well-behaved switching transformers that'll work together.
     
  9. maycat

    maycat

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    Yep - a JCC electronic transformer on the tension wire ...
     
  10. maycat

    maycat

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    Not the issue - the tape runs fine - it's an LED driver from Tagra lighting. Used them elsewhere without a problem.
     
  11. bernardgreen

    bernardgreen

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    Preferably use an inductive transformer for the tension wire.
     
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