Page 1 of 3 123 LastLast
Results 1 to 10 of 23

Thread: Overseas Transformer's

  1. #1
    Join Date
    Mar 2013
    Location
    USA
    Posts
    642

    Overseas Transformer's

    230V 50Hz overseas (Singapore) is like our 120V 60Hz here in the US. What I mean by that is both voltages to ground are the nominal voltages. They are not phase to phase voltage but are phase to ground voltages. If I want to fuse a .5 KVA 230V to 115V transformer, I will use a 3A primary fuse and nothing on my secondary. But, I should not fuse a grounded conductor right? So the 230V coming into the transformer will be 230V from 1 leg to ground. So do I just fuse one line of the transformer? Anyone have any experience/insight into this?
    Time is of the essence, and I am low on essence. ~ Graham Hill

  2. #2
    Join Date
    Sep 2008
    Location
    UK
    Posts
    6,344
    Quote Originally Posted by fifty60 View Post
    230V 50Hz overseas (Singapore) is like our 120V 60Hz here in the US. What I mean by that is both voltages to ground are the nominal voltages. They are not phase to phase voltage but are phase to ground voltages.
    In UK, usual distribution is from the star (wye) secondary of a 400V line to line so 230V line to neutral transformer.
    The majority of residential and quite a few light commercial premises are served with 230V line to neutral. But note that is line to neutral.
    Don't confuse neutral with ground.

  3. #3
    Join Date
    Mar 2013
    Location
    USA
    Posts
    642
    The neutral is still grounded though right? I cannot fuse a grounded conductor because I never want to break my path to ground. For 230V European equipment, is it common to have the neutral phase grounded? I am taking my transformer from a 230V single phase source, and stepping it down to 115. I know that one of my secondary legs will be grounded. Would you recommend that I fuse both legs of the primary, or should only one of the primary lines be fused?
    Time is of the essence, and I am low on essence. ~ Graham Hill

  4. #4
    Join Date
    Sep 2008
    Location
    UK
    Posts
    6,344
    Quote Originally Posted by fifty60 View Post
    The neutral is still grounded though right?
    Yes, as a rule. there are some exceptions. But neutral remains the neutral, whether grounded or not.

    Quote Originally Posted by fifty60 View Post
    I cannot fuse a grounded conductor because I never want to break my path to ground.
    Agreed.

    Quote Originally Posted by fifty60 View Post
    For 230V European equipment, is it common to have the neutral phase grounded?
    Neutral phase is a rather odd term..
    It is common to have the neutral grounded (earthed), usually at the local distribution transformer.
    What we have for our local supply is an 11kV delta to 400V star 1500kVA transformer. It supplies line to neutral voltage to a number of residences with the load being distributed between the phases.

    Quote Originally Posted by fifty60 View Post
    I am taking my transformer from a 230V single phase source, and stepping it down to 115. I know that one of my secondary legs will be grounded. Would you recommend that I fuse both legs of the primary, or should only one of the primary lines be fused?
    I would not recommend fusing the neutral, grounded or otherwise.
    Last edited by Besoeker; 08-22-13 at 04:01 PM.

  5. #5
    Join Date
    Mar 2013
    Location
    USA
    Posts
    642
    Definitely a strange sight for us in the States to get used to. Wherever there is 230V there is only one line that is fused for heaters, motors, transformers. Is that really the normal way of doing things "over there" in the 50Hz lands?
    Time is of the essence, and I am low on essence. ~ Graham Hill

  6. #6
    Join Date
    Mar 2013
    Location
    USA
    Posts
    642
    The fact that the neutral is not fused is not hard to believe, because that is definitely the rule here as well, it is just the sight of seeing 230V with one line fused that is odd.
    Time is of the essence, and I am low on essence. ~ Graham Hill

  7. #7
    Join Date
    Dec 2012
    Location
    Placerville, CA, USA
    Posts
    8,588
    Quote Originally Posted by fifty60 View Post
    ... it is just the sight of seeing 230V with one line fused that is odd.
    I feel that! Just do not spend a lot of time looking for the neutral that you just know is always there somewhere when you are trying to use an imported 120V load.

    It may be easier if you think of their system, as was mentioned earlier, as either 230/460 3-wire or 400Y/230 4-wire instead of just "230".

  8. #8
    Join Date
    Mar 2013
    Location
    USA
    Posts
    642
    The 4 wire 400 Star is easy enough to understand, 400V between phases, 230V phase to neutral wire. I don't quit understand the 230/460.

    I know that our phase to neutral 120V is really split phase, or half of a 240V phase. The 240V here in the states is 240V phase to phase, but in actuality it is only one phase, single phase.

    Is the 230/460 really two 230V phases 180 degrees out of phase with each other? This would require a single phase of 460V, right?
    Time is of the essence, and I am low on essence. ~ Graham Hill

  9. #9
    Join Date
    Dec 2012
    Location
    Placerville, CA, USA
    Posts
    8,588
    Quote Originally Posted by fifty60 View Post
    The 4 wire 400 Star is easy enough to understand, 400V between phases, 230V phase to neutral wire. I don't quit understand the 230/460.

    I know that our phase to neutral 120V is really split phase, or half of a 240V phase. The 240V here in the states is 240V phase to phase, but in actuality it is only one phase, single phase.

    Is the 230/460 really two 230V phases 180 degrees out of phase with each other? This would require a single phase of 460V, right?
    Basically, and I cannot say with certainty that it is used much at all over there. The L1-to-L2 phase voltage would be 460.

  10. #10
    Join Date
    Mar 2013
    Location
    USA
    Posts
    642
    But I can be certain that whenever I see 230V 50Hz it will be 400Y or 230/460? Either way if 230V is the nominal voltage, it will be referenced to ground. 400 or 460V will be between phases.

    I am reading through some older posts hoping to get a better intuition for the power circuit I am dealing with. Current is indeed flowing from the 230V leg through the load and back to the transformer on the neutral leg. Even though the transformer leg is grounded, the current does not travel to ground at this point, but goes back through the transformer and through the load, and then through the neutral again, and then through the transformer, load, neutral again, of course, switching directions 100 times a second. Is this correct? The 400Y distribution transformer is grounded, and the neutral is connected to this ground, but no current flows to ground unless another conductor in the system is grounded through a ground fault?

    The above description also holds for secondary's of control transformers? Anyone willing to elaborate on that would be much appreciated.

    Also, is there an official source that I can look up say, for Singapore or Korea that I can look at and determine what kind of power system they have? I know there are several on the net, but I would like to have one recommended from the forum.

    Also, it is easy to find diagrams of 460V transformers that have two fuses on the primary. If anyone can find diagrams or resources showing fusing for 230V transformers on a 400Y or 230/460V system, that would also be appreciated. Are there any arguments for grounding both primary legs of a 230V circuit derived from a 400Y source?
    Last edited by fifty60; 08-22-13 at 09:25 PM.
    Time is of the essence, and I am low on essence. ~ Graham Hill

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •