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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

    Zoomup:

    The IEEE has looked into this matter before.

    https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8303690


    Z.




    Thanks Zoomup:


    Very interesting article from the IEEE. 


    WE seem to be heading down the RCD route though:


     I noted the Electrical Safety First comment:

    "If you are charging from a 13A mains socket in your home, ensure the wiring in your property has been checked prior to doing so. Old wiring may not be able to cope with the demand from charging your vehicle overnight and risk a fire in your property."  


    Most houses will have a Type A RCD if any, and these won't pick up the DC element that the NICEIC is staying as a must.  (ESF was once part of the NICEIC).  Shouldn't they just say get an electrician to install dedicated circuit?

    If we don't get the message clear from the outset we know people will just cut corners, this is the chance to get it right now.

    People need to view it in the same way Gas is viewed especially due to the direct/indirect contact and being 'outside the safety cage'.


    Thanks



    Simon

Reply
  • 0

    Zoomup:

    The IEEE has looked into this matter before.

    https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8303690


    Z.




    Thanks Zoomup:


    Very interesting article from the IEEE. 


    WE seem to be heading down the RCD route though:


     I noted the Electrical Safety First comment:

    "If you are charging from a 13A mains socket in your home, ensure the wiring in your property has been checked prior to doing so. Old wiring may not be able to cope with the demand from charging your vehicle overnight and risk a fire in your property."  


    Most houses will have a Type A RCD if any, and these won't pick up the DC element that the NICEIC is staying as a must.  (ESF was once part of the NICEIC).  Shouldn't they just say get an electrician to install dedicated circuit?

    If we don't get the message clear from the outset we know people will just cut corners, this is the chance to get it right now.

    People need to view it in the same way Gas is viewed especially due to the direct/indirect contact and being 'outside the safety cage'.


    Thanks



    Simon

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