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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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  • Former Community Member
    0 Former Community Member

    Zoomup:

    More E.V. charging safety concerns.

    https://www.dailymail.co.uk/sciencetech/article-7086061/Electric-vehicle-drivers-UK-risking-death-electrocution-charging-car-home.html


    Z.




    Amongst the dangers claimed is fire risk from daisy chaining extension leads which is technically unconvincing. Worries about daisy chaining seem to originate from countries with unfused plugs where chaining multi-way leads can allow overloads. Coiled cables is a much more likely fire hazard and isn't even mentioned. The most significant danger in daisy chained leads is probably indoor-rated connectors in the middle of the chain getting rained on and associated shock risk but it's hardly unique to electric cars. Take a look outside at Christmas time and you'll see plenty of chained extension leads in people's front gardens, sometimes with plastic bags, tape or upturned buckets for "weather protection", often without.


    As Simon said the point of a 13A domestic socket is that unskilled people can plug things into them and have a reasonable expectation of safety. Electric cars are hardly the only thing an average person might plug in with a long-term 10 A load, which basically leaves you with worries about class 1 appliances outdoors on PME systems.

Reply
  • Former Community Member
    0 Former Community Member

    Zoomup:

    More E.V. charging safety concerns.

    https://www.dailymail.co.uk/sciencetech/article-7086061/Electric-vehicle-drivers-UK-risking-death-electrocution-charging-car-home.html


    Z.




    Amongst the dangers claimed is fire risk from daisy chaining extension leads which is technically unconvincing. Worries about daisy chaining seem to originate from countries with unfused plugs where chaining multi-way leads can allow overloads. Coiled cables is a much more likely fire hazard and isn't even mentioned. The most significant danger in daisy chained leads is probably indoor-rated connectors in the middle of the chain getting rained on and associated shock risk but it's hardly unique to electric cars. Take a look outside at Christmas time and you'll see plenty of chained extension leads in people's front gardens, sometimes with plastic bags, tape or upturned buckets for "weather protection", often without.


    As Simon said the point of a 13A domestic socket is that unskilled people can plug things into them and have a reasonable expectation of safety. Electric cars are hardly the only thing an average person might plug in with a long-term 10 A load, which basically leaves you with worries about class 1 appliances outdoors on PME systems.

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