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Double wound safety transformer for EV supply.

SL1
Hi everyone, I have only posted once before so thanks to anyone who replies!


I am following on from the earlier "70 volt PEN conductor not allowed to exceed post", and looking into supplying a client with an electric vehicle power supply from a three phase isolating transformer BS 7671 722.413 (1.2): " The circuit shall be supplied through a fixed isolating transformer.."


The general consensus seems to be that an external IP box with an RCD (Type B) and a tethered lead is the standard to follow, and this may be the only option with a 230 volt domestic supply, but why not use a 3 phase 400 volt step down or tapped, safety double wound isolation transformer in a standard 100 -200 ampere or above industrial units/sheds?

( Subject to load and diversity).


The answer often stated when I have asked sparks/engineers is that in-rush current are too high but a type D CB BS 60898 will 'let through' the in-rush ( the transformer manufacturer agrees), and will still give at 5 seconds- (final circuit exceeding 32 A) 0.44 ohm EL ( 10oC) , so is achievable in many situations local to Birmingham.


I was then going to run a fused cable out to an external isolated IP 65 box with a Type 2 socket to IP44 or above ( 722.55.101).


Isn't it better to engineer a solution to the upcoming electric charger deluge, rather than buying (insert well known manufacturer name here), and lots of single phase loads usually dumped onto L1?


I would be interested in any thoughts or problems you may consider....





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  • 0
    Ah, I just said the cable was interesting - I wasn't suggesting you used it to supply your charge point. I always found it a bit odd that in the UK we mostly only seem to have a choice between T&E (which falls well below most world standards) and SWA (which seems overkill for most circumstances) - so I'm always interested in how they do things elsewhere.

     

    If the cable is a derivative of a SY cable the IET on-site guide specifically says that we couldn't use this type of cable: " every item of equipment must comply with a British or Harmonised Standard"   and " SY, YY and CY cables are not made to British or Harmonised standards."



    Ah, that old Chestnut again. The regulation they're referring to (133.1.1) actually goes on to say "In the absence of such a standard, reference shall be made to the appropriate International (IEC) standard or the appropriate standard of another country." (my emphasis). I'll let you work out if what the OSG says is an absolute truth or just a (over) simplification suited for a short guide book whose purpose is to avoid anything complicated like calculations or extra reading.


      - Andy.
Reply
  • 0
    Ah, I just said the cable was interesting - I wasn't suggesting you used it to supply your charge point. I always found it a bit odd that in the UK we mostly only seem to have a choice between T&E (which falls well below most world standards) and SWA (which seems overkill for most circumstances) - so I'm always interested in how they do things elsewhere.

     

    If the cable is a derivative of a SY cable the IET on-site guide specifically says that we couldn't use this type of cable: " every item of equipment must comply with a British or Harmonised Standard"   and " SY, YY and CY cables are not made to British or Harmonised standards."



    Ah, that old Chestnut again. The regulation they're referring to (133.1.1) actually goes on to say "In the absence of such a standard, reference shall be made to the appropriate International (IEC) standard or the appropriate standard of another country." (my emphasis). I'll let you work out if what the OSG says is an absolute truth or just a (over) simplification suited for a short guide book whose purpose is to avoid anything complicated like calculations or extra reading.


      - Andy.
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