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 AJJewsbury over 5 years ago

How is it a protective conductor if it's not used for ADS because the means of protection against electric shock is Electrical Separation? (See definition of Protective Conductor in Part 2 - specifically, it's definitely not "PE" in this instance, more "FE".)

I'd say it's still a protective conductor - but as you say unearthed (so definitely not FE, more like keep the P, loose the E). I'd say it compares directly with the insulated conductor that section 418.3 demands connects exposed-conductive-parts together (but not to earth) on a separated circuit - so as to provide protection from shock on 2nd faults (otherwise we'd have a shock risk between two different exposed-conductive-parts on 2nd fault) - 418.3.4 it calls it a 'protective bonding conductor' (I might argue about the word bonding in there, but anyhow) it definitely refers to it as a protective conductor. ADS on 2nd fault doesn't stop the basic approach being separation (as per reg 418.3.7) although if you connect the protective conductor to a live conductor ADS should then happen on 1st fault rather than 2nd as we're in effect creating a separated circuit with the first fault already present.

(It might have been simpler if 413 talked about one class I item rather than one item of current-using equipment - since the shock risks between exposed-conductive-parts are the same regardless of whether they're part of an appliance or part of an accessory)

- Andy.
Cancel
Vote Up 0 Vote Down

Cancel

Reply

0 AJJewsbury over 5 years ago

How is it a protective conductor if it's not used for ADS because the means of protection against electric shock is Electrical Separation? (See definition of Protective Conductor in Part 2 - specifically, it's definitely not "PE" in this instance, more "FE".)

I'd say it's still a protective conductor - but as you say unearthed (so definitely not FE, more like keep the P, loose the E). I'd say it compares directly with the insulated conductor that section 418.3 demands connects exposed-conductive-parts together (but not to earth) on a separated circuit - so as to provide protection from shock on 2nd faults (otherwise we'd have a shock risk between two different exposed-conductive-parts on 2nd fault) - 418.3.4 it calls it a 'protective bonding conductor' (I might argue about the word bonding in there, but anyhow) it definitely refers to it as a protective conductor. ADS on 2nd fault doesn't stop the basic approach being separation (as per reg 418.3.7) although if you connect the protective conductor to a live conductor ADS should then happen on 1st fault rather than 2nd as we're in effect creating a separated circuit with the first fault already present.

(It might have been simpler if 413 talked about one class I item rather than one item of current-using equipment - since the shock risks between exposed-conductive-parts are the same regardless of whether they're part of an appliance or part of an accessory)

- Andy.
Cancel
Vote Up 0 Vote Down

Cancel

Children

No Data

Double wound safety transformer for EV supply.

Community Rules & Guidelines