Turns ratio
Updated 2026-10-27
Data records
- The turns ratio of a transformer is the ratio of the number of turns in the primary winding to the number of turns in the secondary winding; it is dimensionless and is estimated in the field from the ratio of the primary voltage to the secondary voltage with the secondary winding open.
- Turns ratio is read by transformer turns ratio testers, which apply a low alternating test voltage to one winding, measure the voltage induced in the other and display the ratio together with the excitation current and the phase displacement between the two windings.
- In a healthy winding the measured ratio departs from the nameplate ratio only by the small fraction that the exciting current drops across the winding impedance, so a reading well outside that fraction points to shorted turns, an open winding or a tap changer left on a position other than the nameplate one.
- The quantity is written Turns ratio. Value: Turns ratio.
Sources
- Electrical Testing Reference editorial taxonomy, Electrical Testing Reference editorial taxonomy of test methods, 2026-10 edition, Electrical Testing Reference. Held as: Own observation.
Changelog (9 entries)
| Date | Revision | Change |
|---|---|---|
| 2026-10-27 | created (qty.turns-ratio.definition) | |
| 2026-10-27 | revised (qty.turns-ratio.definition) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (qty.turns-ratio.definition) | |
| 2026-10-27 | created (qty.turns-ratio.measured-by) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (qty.turns-ratio.measured-by) | |
| 2026-10-27 | created (qty.turns-ratio.nameplate-deviation) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (qty.turns-ratio.nameplate-deviation) | |
| 2026-10-27 | created (qty.turns-ratio.title) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (qty.turns-ratio.title) |
Cite this page
Cite the governing standard for the fact itself; cite this page as the finding aid.
"Turns ratio." Test Instrument Reference. 2026-10-27. https://www.testinstrumentreference.com/quantities/turns-ratio/.
Test Instrument Reference, Turns ratio (Oct. 27, 2026), https://www.testinstrumentreference.com/quantities/turns-ratio/.
@misc{etr-quantities-turns-ratio,
title = {Turns ratio},
howpublished = {\url{https://www.testinstrumentreference.com/quantities/turns-ratio/}},
organization = {Test Instrument Reference},
publisher = {Test Instrument Reference},
year = {2026},
note = {last substantive change 2026-10-27}
}{{cite web |title=Turns ratio |website=Test Instrument Reference |publisher=Test Instrument Reference |url=https://www.testinstrumentreference.com/quantities/turns-ratio/ |date=2026-10-27 |access-date=}}