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# 3 phase turns ratio formula

1.  Junior Member
Join Date
Jul 2020
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Reputation ## 3 phase turns ratio formula

What is the turns ratio for a delta wye 138000/12470 XFMR. What is the proper formula? Thanks  Reply With Quote

2. Originally Posted by Js20981 What is the turns ratio for a delta wye 138000/12470 XFMR. What is the proper formula? Thanks
First step is to only use phase to ground voltages.
For Delta, Line-to-Line = Phase-to-Ground voltages.
For Wye, SQRT(3) * Line-to-Line = Phase-to-Ground voltages. Vp=12470/SQRT(3)=12470/1.732=7199.8V

TTR=138000V/7200V=~19.166

Math should be correct minus rounding errors.  Reply With Quote

3. as the previous post already explained
These questions are hard to answer.

Even NETA is vague on the exams.

Given 138,000 to 12470
They do not tell you the connections( I protested these questions)

138,000 probably a line to line voltage so you would assume a delta
12470 probably a wye voltage. 12470/square root 3=7199.56=7200

138,000/7200=19.1666  Reply With Quote

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