Toroidal transformers

Discussion in 'Electricians' Talk' started by unphased, Jul 10, 2018.

  1. unphased

    unphased Screwfix Select

    Swapping out a failed 12V 80VA by Ikea toroidal Tx for a tramway lighting system with 3 x 20W 12V halogen lamps.

    I didn't know the rating when I was ordering so I've ordered a 160VA. Question is will this still be okay for the load? Will it pull the 6A RCBO out I'm using on the lighting circuit?

    I've ripped the guts out of the Ikea 'can' and placed the new Tx inside it.
     
  2. Bazza

    Bazza Well-Known Member

    Err. For simple lights, Watts = VA
    So a much cheaper 60VA transformer would have been plenty big enough.

    Ahh. I’ve just clocked it’s you UP.

    You need a much bigger transformer, maybe 500watts will be about big enough. And you’ll need to get a three phase supply from your lekky people. You’ll need at least a 63A, D curve MCB for that bad boy.
     
    DIY womble likes this.
  3. unphased

    unphased Screwfix Select

    Read the question, Bazza. I don't know whether using twice the capacity will harm the Tx? And in the past when I've used these things the Tx pulled out B curve mcb's so wondering if this will do the same? I just don't know. May need a C curve. I also don't know whether electronic Tx can work without issues on these types of lighting? Theoretically it would, just matching the VA as you say, but why were toroidal Tx used if electronic would work? Is it cuz the technology wasn't around twenty years ago?
     
  4. Pollowick

    Pollowick Well-Known Member

    Transformers are cheap relative to an SMPS ...

    What you may find is that the output voltage is a little higher than expected when on 40% load ... Try connecting the transformer up and measuring with no lamp fitted, then one, two, three ... eight fitted an you will see the change.

    With three lamps fitted you will only pull the 60VA needed plus the transformer losses, say another 20-30 VA, so under 100 and overall under 0.5A.
     
  5. Lectrician

    Lectrician Screwfix Select

    You could fit a soft start dimmer if it did nuisance trip the B type. Best not to use electronic transformers on those types of light fittings as you are meant to keep the wiring as short as possible on the electronic types to minimise EMF. With those fittings your essentially introducing an aerial :D
     
  6. unphased

    unphased Screwfix Select

    Thanks both. In the end it worked perfectly. No problems at all. Worried over nothing.:rolleyes:
     
  7. HarDeBloodyHarHar

    HarDeBloodyHarHar Active Member


    ....so far!
     

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