Three phase transformers question

[Surefire]

Hi All

Could anyone confirm the following:

A 3 phase transformer has delta wound primaries and star wound secondries. The turns ratio is 1:1. If 415v is applied to the primary, will the secondary voltage be 240v?

I think it will because the secondary output voltage will be: primary line voltage divided by root 3

Is this correct?

 

[High Tower]

Thats correct,

A primary 400v applied to a delta star transformer gives a Phase and line voltage of 400v with the line current being x1.72 of the phase current.

On the secondary (Star) you still have a line voltage of 400v but utilising the centre (neuteral) point a phase voltage of 230v is applicable, with the current for both being equal in magnitude.

Hence the 1.1 ratio.