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230V Supply from 400V Line to Line in a Control panel

Pabindu Gamage

Hi, 


I have a situation where I need to install a 230V control system which draws about Max 5A ( at230V) inside a existing Dinrail enclosure. 
However, the incoming (feeder) cable of this enclosure is a 3 Core + Earth and doesn't have a Neutral, as the load is 3 phase with no neutral.

My task is to provide a 230V supply for a control equipment that we are going to install inside this enclosure. I am struggling as there is no neutral available. 
feeder is very long hence we cannot afford to run a neutral from the SDB to this enclosure.  either. 

1) Would it be possible to mount a small control transformer and feed this with 400V supply and then generate a 230V supply ? (below link)

https://www.yesss.co.uk/eris-400va-panel-transformer-230400v-primary-122448110240v-secondary?srsltid=AfmBOoq0MCaJYskcQovSxGEfzGITtVWGUpqrmsWnTT7WLwGIsOa1xMz0


2) and if so, will this be a floating neutral ? and how do I make the neutral 0V then if required? from a practical point of view.

Thank you in advance for your support. 

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  • 0

    Would it not be more prudent to replace the 3 Core + Earth for a 4 core + Earth?  This would allow for other single phase devices like a dual plug/socket arrangement to plug in a tester or a light to the maintenance technicians laptop.

  • 0 in reply to Sergio Fernandez

    Its quite often not all that practical to retrofit that over a long distance, especially for a small load increment, and also means that if there is RCD cover it needs to be changed for 4 pole sensing instead of 3. The 400:230 transformers, and their bigger cousins 690:400 exist for a reason, and delta (no neutral) distro is quite common in large factory settings.

    Even a star delta motor starter does not actually need the star point to be neutralled....

    Occasionally one comes across 230V loads connected between 1 phase and CPC which is very naughty and relies on the TNC-S supply NE  bond. 

    Mike

  • 0 in reply to Sergio Fernandez
    Pabindu Gamage said:
    feeder is very long hence we cannot afford to run a neutral from the SDB to this enclosure.  either. 

    Not quite sure how a neutral could be added, especially if the cable is SWA; but if that has been ruled out on the basis of cost, replacing the whole cable is also excluded.

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