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Double wound safety transformer for EV supply.

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 David Stone over 5 years ago

There was a great deal of push from the BBC about using the cars batteries for mains backup but in my view it is useless. The car battery will be cycled when not driving and will have reduced life. Clearly getting free batteries is of interest to renewables providers, but that is their job not the car owner. Having a car with a battery in an unknown charge state is also useless unless you live on a small island (as in the BBC piece), unless one can program the maximum and minimum status long before a journey is to be made. It is suggested that money will be paid for charge used by the grid, but this obviously needs to be at a very high rate to make it worthwhile for the car owner who needs a special car with reverse charge and a new battery more often. I doubt many people will be interested!
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0 David Stone over 5 years ago

There was a great deal of push from the BBC about using the cars batteries for mains backup but in my view it is useless. The car battery will be cycled when not driving and will have reduced life. Clearly getting free batteries is of interest to renewables providers, but that is their job not the car owner. Having a car with a battery in an unknown charge state is also useless unless you live on a small island (as in the BBC piece), unless one can program the maximum and minimum status long before a journey is to be made. It is suggested that money will be paid for charge used by the grid, but this obviously needs to be at a very high rate to make it worthwhile for the car owner who needs a special car with reverse charge and a new battery more often. I doubt many people will be interested!
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Double wound safety transformer for EV supply.

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