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Balanced 3 Phase Supply for EVC

Mark Fleming

Hi,

Please could someone advise on the following regarding EV chargers on a balanced 3 phase supply. 

We are proposing to install 3 x 75kw DC rapid chargers from a new DNO connection solely for the EV chargers. The chargers themselves only require 3 phase & earth and the only 230v supply from the new connection is a small anti-condensation heater within the feeder pillar (20w). 

Can I therefor still use the rule of thumb from CoP J4 as Regulation 722.411.4.1 (i) has now been removed from amendment 2? 

When I calculate using Regulation 722.411.4.1 (ii) I end up with a minus number so I assume this shows an earth electrode & PME supply is not suitable?

Thank you in advance.

Mark

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  • 0
    Mark Fleming said:
    The chargers themselves only require 3 phase & earth

    So there is no neutral to lose.

  • 0 in reply to Chris Pearson

    note that no neutral does not always mean all 3 line currents are balanced, you can have a delta of 3 different resistances,  3 different line currents, and no neutral current, so if the PEN goes O/C there is no ground pull.

    Mike.

  • 0 in reply to Chris Pearson
    Chris Pearson said:
    So there is no neutral to lose.

    Not quite - the Neutral may be there to provide the PE at the service head.

    However, in this case, OP has confirmed they are likely to use the N of the TPN for small single-phase loads at least (anti-condensation heaters)

  • 0 in reply to gkenyon

    Yes, I noticed that, but if it isn't part of the charger, does it matter?

  • 0 in reply to mapj1

    Is that likely within the chargers themselves? My first thought was that by no means all cars can draw 3 phases, but then I realised that the chargers are DC so unless they became faulty, how would an imbalance arise?

  • 0 in reply to Chris Pearson
    Chris Pearson said:
    Yes, I noticed that, but if it isn't part of the charger, does it matter?

    Yes, the demand that produces the neutral current is based on the phase balance of the whole installation as defined in BS 7671. How you define what the extent of the installation is based on the definition of that term in BS 7671 is another question.

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  • 0 in reply to Chris Pearson
    Chris Pearson said:
    Yes, I noticed that, but if it isn't part of the charger, does it matter?

    Yes, the demand that produces the neutral current is based on the phase balance of the whole installation as defined in BS 7671. How you define what the extent of the installation is based on the definition of that term in BS 7671 is another question.

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