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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....





Parents
  • 0

    "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?



    The main problem with using 13A sockets isn't so much the wiring as the sockets themselves - some brands have been found to be rather lacking when called on to carry the full 13A for many hours - they've been overheating ? (hence the new requirement for new "EV" marked sockets.)


    Where a 13A socket is used the EV connection lead will have to incorporate a box containing a protection system (like the contents of a wall pod) - some of these incorporate B-type RCD or other means of tripping if d.c. leakage exceeds 6mA - so protecting any upstream A-type (or AC-type) RCDs from being blinded - so in practice there might not be a too much of problem.


      - Andy.
Reply
  • 0

    "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?



    The main problem with using 13A sockets isn't so much the wiring as the sockets themselves - some brands have been found to be rather lacking when called on to carry the full 13A for many hours - they've been overheating ? (hence the new requirement for new "EV" marked sockets.)


    Where a 13A socket is used the EV connection lead will have to incorporate a box containing a protection system (like the contents of a wall pod) - some of these incorporate B-type RCD or other means of tripping if d.c. leakage exceeds 6mA - so protecting any upstream A-type (or AC-type) RCDs from being blinded - so in practice there might not be a too much of problem.


      - Andy.
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