Confused about transformer windings

Discussion in 'The Projects Forum' started by electrophile, Oct 27, 2013.

  1. electrophile

    Thread Starter Member

    Aug 30, 2013
    I have a toroidal transformer which has two 115V primaries and two secondaries rated at 25VA each (2x18V each capable of delivering 1.389A). I've attached the datasheet here. I'm a bit confused about using this with 230VAC primary voltage. Can I connect the two primaries in series (blue+green connected, 230V mains AC between Brown and Violet) to get 230VAC and the two secondaries in parallel (Red+Yellow and Black+Orange) to get 18V at 2.778A? Color codes are specific to this datasheet.
  2. cornishlad

    Active Member

    Jul 31, 2013
    I assume you mean the colours on your transformer leads are the same as the datasheet. In which case your assumptions are correct. split primaries and secondaries are normal.
  3. MaxHeadRoom


    Jul 18, 2013
    The attraction with Toroids, they are easy to add an overwind if needed, either a separate winding or add to, or subtract from an existing secondary.
    You have to keep the original Va rating in mind when doing this.