This discussion is locked.

You cannot post a reply to this discussion. If you have a question start a new discussion

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....

Parents

0 gkenyon over 5 years ago

mapj1:

Some of us are quite happy to specify and use SY and similar in situations where we think it is the best technical solution. It is important to realise that the braid is really best used as an EMC thing and not intended either as armour against attack by sharp objects nor are the fine strands good as a high current CPC. But for flexibility and shielding, ideal.

Equally there are those of us who consider BS7671 to be a guide, and not the last word in wiring standards, though I suspect to many others that is tantamount to heresy. However, I mainly work in a research environment, and as that is always pushing at non standard solutions, it probably colours my thinking somewhat.

Also, note that most SY cable is not "submersible" or waterproof, and may not be UV stable.

Therefore, even if in a dedicated duct, if the cable sits in water for some time, its insulation resistance suffers.
Cancel
Vote Up 0 Vote Down

Cancel

Reply

0 gkenyon over 5 years ago

mapj1:

Some of us are quite happy to specify and use SY and similar in situations where we think it is the best technical solution. It is important to realise that the braid is really best used as an EMC thing and not intended either as armour against attack by sharp objects nor are the fine strands good as a high current CPC. But for flexibility and shielding, ideal.

Equally there are those of us who consider BS7671 to be a guide, and not the last word in wiring standards, though I suspect to many others that is tantamount to heresy. However, I mainly work in a research environment, and as that is always pushing at non standard solutions, it probably colours my thinking somewhat.

Also, note that most SY cable is not "submersible" or waterproof, and may not be UV stable.

Therefore, even if in a dedicated duct, if the cable sits in water for some time, its insulation resistance suffers.
Cancel
Vote Up 0 Vote Down

Cancel

Children

No Data

Double wound safety transformer for EV supply.

Community Rules & Guidelines