Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Helpful Answer
  • Replies 15 replies
  • Helpful Answers 1 Helpful answer
  • Subscribers 39 subscribers
  • Views 398 views
  • Users 0 members are here
Options
You may also be interested in

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. 

Parents
  • 0

    Yes, a 400 to 230V transformer is a common solution to this sort of problem. Just connect one pole of the output to the supply circuit c.p.c. to make it N (and hence a small TN-S system). (Depending on the situation, other options might also be considered - e.g. a separated (floating) system).

       - Andy.

  • 0 in reply to AJJewsbury

    Thank you Andy, 
    This really helps. I thought of the same but then I was a little worried if I am making a separate earthing island. 
    Thank you for your advice.

  • 0 in reply to Pabindu Gamage

    I was a little worried if I am making a separate earthing island. 

    By using the supply c.p.c. you make sure it's all part of the same earthing system - so no worries on that point.

    In the case of an earth fault on the control circuit, the immediate fault loop will only consist of the control circuit back through the secondary winding of your transformer (via your PE-N link), but that current has to be "driven" by a corresponding current in the primary - which is limited by the L-L loop impedance at that point. So Zs calculations (if needed) get a bit more complicated, as as well as R1+R2 of your control circuit to consider there's the overall impedance of the transformer plus a proportion of the L-L loop that supplies that (the proportion depending on the winding ratio of the transformer). Note that small transformers can have relatively high impedances. 

       - Andy. 

Reply
  • 0 in reply to Pabindu Gamage

    I was a little worried if I am making a separate earthing island. 

    By using the supply c.p.c. you make sure it's all part of the same earthing system - so no worries on that point.

    In the case of an earth fault on the control circuit, the immediate fault loop will only consist of the control circuit back through the secondary winding of your transformer (via your PE-N link), but that current has to be "driven" by a corresponding current in the primary - which is limited by the L-L loop impedance at that point. So Zs calculations (if needed) get a bit more complicated, as as well as R1+R2 of your control circuit to consider there's the overall impedance of the transformer plus a proportion of the L-L loop that supplies that (the proportion depending on the winding ratio of the transformer). Note that small transformers can have relatively high impedances. 

       - Andy. 

Children
No Data

Community Rules & Guidelines