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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 mapj1 over 5 years ago

Electrically Modes 2 and 3 are very similar, in that the charger is in the car. Mechanically it looks quite different. The advantage of mode 2 is that the you take the bit that talks to the car to turn on the charger with you and can use an ordinary mains supply. The downside is you have no idea what protection or RCDs etc the building wiring provides in any given location.

Nice image of the modes

Mode 4 (AC to DC conversion at the building) I see as more use for vans and lorries where more power is needed, and the chances of needing a charge in a strange place is less likely.

I guess if the vehicle reverse charging idea (cars as generators) takes off, there will be another mode, where a box of magic allows your car to think it is plugged in so it will sync to a spoofed grid, and work as a stand alone mains generator for people who are camping and so on and fancy a mains supply in the middle of a field. Closely followed by a jump lead mode for folk who over did it and can't get out of the field.
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0 mapj1 over 5 years ago

Electrically Modes 2 and 3 are very similar, in that the charger is in the car. Mechanically it looks quite different. The advantage of mode 2 is that the you take the bit that talks to the car to turn on the charger with you and can use an ordinary mains supply. The downside is you have no idea what protection or RCDs etc the building wiring provides in any given location.

Nice image of the modes

Mode 4 (AC to DC conversion at the building) I see as more use for vans and lorries where more power is needed, and the chances of needing a charge in a strange place is less likely.

I guess if the vehicle reverse charging idea (cars as generators) takes off, there will be another mode, where a box of magic allows your car to think it is plugged in so it will sync to a spoofed grid, and work as a stand alone mains generator for people who are camping and so on and fancy a mains supply in the middle of a field. Closely followed by a jump lead mode for folk who over did it and can't get out of the field.
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Double wound safety transformer for EV supply.

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