Transformer Vectors

Transformer Vectors

 

This was a topic brought up on the job and I figured I would address it in a very general post. This will not go too in depth but will help you understand how a vector is configured and possibly understand what you are dealing with on the job.

 

What is a vector? A vector is a quantity having direction as well as magnitude, especially as determining the position of one point in space relative to another.

Why do we care about vectors?  Vectors are an important piece of information when applied to transformers. As a test technician, we need to know the configuration in order to test the equipment properly.

 

 

Winding connection designations:

Vectors give a graphic representation of winding displacement.

  • First Symbol: for High Voltage: Always capital letters.
  •  D=Delta, Y=Star (Wye), Z=Interconnected star, N=Neutral
  • Second Symbol: for Low voltage: Always Small letters.
  •  d=Delta, y=Star (Wye), z=Interconnected star, n=Neutral.
  • Third Symbol: Phase displacement expressed as the clock hour number (1,6,11)
  • Example – Dyn1
    Transformer has a delta connected primary winding (D) a star connected secondary (y) with the star point brought out (n) and a phase shift of 30 deg lagging (1).
  • The point of confusion is occurring in notation in a step-up transformer. As the IEC60076-1 standard has stated, the notation is HV-LV in sequence. For example, a step-up transformer with a delta-connected primary, and star-connected secondary, is not written as ‘dY11’, but ‘Yd11’. The 11 indicates the LV winding leads the HV by 30 degrees.
  • Transformers built to ANSI standards usually do not have the vector group shown on their nameplate and instead a vector diagram is given to show the relationship between the primary and other windings.

 

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