wye-delta transformer question

Discussion in 'General Electronics Chat' started by huantran, Jul 3, 2008.

  1. huantran

    Thread Starter New Member

    Jul 3, 2008
    I have a question about transforming 3-phase power.

    I have a project where I need to convert 480/277Y power to
    240V delta + 120V single phase, I need about 15kVA

    I have read that it is not smart to use a y-y transformer, for reasons I cannot figure out. Also, when I search for 3-phase transformers, I find that it is not common to specify the primary coil as wye configured.

    I am a complete noob to this, so here is my question:

    Is there any problem with hooking up a delta-delta transformer to a 480Y source? Most delta-delta transformers are in fact open delta, meaning that there is really only two primary coils instead of 3. I do not need to keep the neutral, I may in fact want it isolated. Conceptually, I think this should be fine, but I may be missing something?

    To get 120V from one of the 240V phases, is it best to just use another single phase transformer? Or should I try to center tap one of the secondary coils somehow?
  2. Pich

    Senior Member

    Mar 11, 2008
    There would be no problem hooking up a Y to a delta transformer as long as the voltages are the same, in this case 460v, the KVA ratings will also need to looked at. The 277 volts does not come into play at all the Y point is not used. there are delta tranformers out there that have a center tap on the secondery side, but depending on the KVA it may be more simple to use a seperate tranformer.
  3. huantran

    Thread Starter New Member

    Jul 3, 2008
    Pich, thanks so much for your input.

    I think I will go with a Square D EE15T151HCT, or on model larger, actually available
    from Grainger!


    one more question, if the transformer is designed for 60Hz, is it possible to run it at 50Hz?
  4. SgtWookie


    Jul 17, 2007
    If it does not specify 50Hz operation in the datasheet, do not assume that it will function properly.

    You can always call Square D and talk with one of their engineers. There's a toll-free number on their website.

    Give them your requirements, and that you're considering the model you mentioned - will that work, or do they have a more appropriate model?