Transformer Turns Ratio
Updated 2026-10-24
| Relationship | Entry |
|---|---|
| Governing standard | IEEE C57.12.00-2021 (IEEE Standard for General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers) |
| Governing standard | IEEE C57.12.01-2020 (IEEE Standard for General Requirements for Dry-Type Distribution and Power Transformers) |
| Governing standard | IEEE C57.18.10-2021 (IEEE Standard Practices and Requirements for Semiconductor Power Rectifier Transformers) |
| Governing standard | IEEE C57.12.90-2021 (IEEE Standard Test Code for Liquid-Immersed Distribution, Power, and Regulating Transformers) |
Data records
- Transformer Turns Ratio is specified for voltage transformers in acceptance testing at clause 7.10.2.B.3 of ANSI/NETA ATS-2025. Value: voltage transformers.
- Transformer Turns Ratio is specified for voltage transformers in maintenance testing at clause 7.10.2.B.4 of ANSI/NETA MTS-2023. Value: voltage transformers.
- Transformer Turns Ratio is specified for step voltage regulators in acceptance testing at clause 7.12.1.1.B.10 of ANSI/NETA ATS-2025. Value: step voltage regulators.
- Transformer Turns Ratio is specified for step voltage regulators in maintenance testing at clause 7.12.1.1.B.8 of ANSI/NETA MTS-2023. Value: step voltage regulators.
- Transformer Turns Ratio is specified for liquid-filled transformers in acceptance testing at clause 7.2.2.B.3 of ANSI/NETA ATS-2025. Value: liquid-filled transformers.
- Transformer Turns Ratio is specified for liquid-filled transformers in maintenance testing at clause 7.2.2.B.3 of ANSI/NETA MTS-2023. Value: liquid-filled transformers.
- Transformer Turns Ratio is specified for small low-voltage air-cooled dry-type transformers in acceptance testing at clause 7.2.1.1.B.3 of ANSI/NETA ATS-2025. Value: small low-voltage air-cooled dry-type transformers.
- Transformer Turns Ratio is specified for small low-voltage air-cooled dry-type transformers in maintenance testing at clause 7.2.1.1.B.3 of ANSI/NETA MTS-2023. Value: small low-voltage air-cooled dry-type transformers.
- Transformer Turns Ratio is addressed in ANSI/NETA ATS-2025.
- Transformer Turns Ratio is addressed in ANSI/NETA MTS-2023.
- Transformer Turns Ratio is addressed in IEEE C57.12.00-2021.
- Transformer Turns Ratio is addressed in IEEE C57.12.01-2020.
- Transformer Turns Ratio is addressed in IEEE C57.18.10-2021.
- Clause 7.1 of IEEE C57.12.90-2021 runs the ratio test at rated or lower voltage and at rated or higher frequency, prefers single-phase excitation on three-phase units when each phase is accessible, and, where a wye neutral is inaccessible, creates a virtual neutral by shorting one phase with the connections of Figure 9.
- IEEE C57.12.90-2021 defines turns ratio as the turns of the high-voltage winding divided by the turns of the low-voltage winding, with a tapped winding taken at the turns for its normal rated voltage, and clause 7.1.1 has the ratio determined for every tap and for the full winding.
- Clause 7.3 of IEEE C57.12.90-2021 gives three ratio methods: two voltmeters read simultaneously and then interchanged, comparison against a transformer of known ratio, and a ratio meter based on a resistance potentiometer circuit that can also indicate polarity, phase relation and phase sequence.
- Clause 7.2 of IEEE C57.12.90-2021 contains no ratio tolerance of its own; it refers the tolerance to clause 9.1 of IEEE C57.12.00-2021.
- The test method is named Transformer Turns Ratio. Value: Transformer Turns Ratio.
Elsewhere in the family
- Instrument Transformer Burden related entry on Revenue Metering Reference
- Instrument Transformer Secondary Grounding related entry on Revenue Metering Reference
- Polarity test related entry on Battery Testing Reference
- Polarity Test related entry on Electrical Testing Reference
- Polarity test related entry on Motor Testing Reference
- Polarity test related entry on Protective Relay Reference
- Polarity test related entry on Revenue Metering Reference
- ANSI/NETA ATS-2025 Standard for Acceptance Testing Specifications related entry on Electrical Testing Reference
- ANSI/NETA MTS-2023 Standard for Maintenance Testing Specifications related entry on Electrical Testing Reference
Sources
- ANSI/NETA ATS-2025, Acceptance Testing Specifications for Electrical Power Equipment and Systems, 2025 edition, NETA. Cited: clause 7.10.2.B.3; clause 7.12.1.1.B.10; clause 7.2.2.B.3; clause 7.2.1.1.B.3. Held as: Purchased single-user copy. Publisher page
- ANSI/NETA MTS-2023, Maintenance Testing Specifications for Electrical Power Equipment and Systems, 2023 edition, NETA. Cited: clause 7.10.2.B.4; clause 7.12.1.1.B.8; clause 7.2.2.B.3; clause 7.2.1.1.B.3. Held as: Purchased single-user copy. Publisher page
- Electrical Testing Reference editorial taxonomy, Electrical Testing Reference editorial taxonomy of test methods, 2026-10 edition, Electrical Testing Reference. Held as: Own observation.
- IEEE C57.12.00-2021, General Requirements for Liquid-Immersed Distribution, Power and Regulating Transformers, 2021 edition, IEEE. Cited: clause 9.1. Held as: Purchased single-user copy. Publisher page
- IEEE C57.12.01-2020, General Requirements for Dry-Type Distribution and Power Transformers, 2020 edition, IEEE. Cited: clause 9.1. Held as: Purchased single-user copy. Publisher page
- IEEE C57.12.90-2021, Test Code for Liquid-Immersed Distribution, Power and Regulating Transformers, 2021 edition, IEEE. Cited: clause 7.1.2, 7.1.3, 7.1.4; clause 7.1, 7.1.1; clause 7.3; clause 7.2. Held as: Purchased single-user copy.
- IEEE C57.18.10-2021, Semiconductor Power Rectifier Transformers, 2021 edition, IEEE. Cited: clause 8.10. Held as: Purchased single-user copy. Publisher page
Obtaining the documents
- ANSI/NETA ATS-2025: publisher catalog or sales page
- ANSI/NETA MTS-2023: publisher catalog or sales page
- IEEE C57.12.00-2021: publisher catalog or sales page
- IEEE C57.12.01-2020: publisher catalog or sales page
- IEEE C57.12.90-2021: publisher catalog or sales page
- IEEE C57.18.10-2021: publisher catalog or sales page
Changelog (23 entries)
| Date | Revision | Change |
|---|---|---|
| 2026-10-24 | created (tests.transformer-turns-ratio.ieeec57-12-90.conditions) | |
| 2026-10-24 | revised (tests.transformer-turns-ratio.ieeec57-12-90.conditions) | |
| 2026-10-24 | review_status unreviewed -> software_reviewed (tests.transformer-turns-ratio.ieeec57-12-90.conditions) | |
| 2026-10-24 | created (tests.transformer-turns-ratio.ieeec57-12-90.definition) | |
| 2026-10-24 | review_status unreviewed -> software_reviewed (tests.transformer-turns-ratio.ieeec57-12-90.definition) | |
| 2026-10-24 | created (tests.transformer-turns-ratio.ieeec57-12-90.methods) | |
| 2026-10-24 | review_status unreviewed -> software_reviewed (tests.transformer-turns-ratio.ieeec57-12-90.methods) | |
| 2026-10-24 | created (tests.transformer-turns-ratio.ieeec57-12-90.tolerance-deferred) | |
| 2026-10-24 | review_status unreviewed -> software_reviewed (tests.transformer-turns-ratio.ieeec57-12-90.tolerance-deferred) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.equipment.instrument.acceptance) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.equipment.instrument.maintenance) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.equipment.regulator.acceptance) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.equipment.regulator.maintenance) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.equipment.transformer-fluid.acceptance) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.equipment.transformer-fluid.maintenance) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.equipment.transformer.acceptance) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.equipment.transformer.maintenance) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.governed-by.ansi-neta-ats) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.governed-by.ansi-neta-mts) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.governed-by.ieee-c57-12-00) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.governed-by.ieee-c57-12-01) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.governed-by.ieee-c57-18-10) | |
| 2026-10-13 | created (tests.transformer-turns-ratio.title) |
Cite this page
Cite the governing standard for the fact itself; cite this page as the finding aid.
"Transformer Turns Ratio." Transformer Testing Reference. 2026-10-24. https://www.transformertestingreference.com/tests/transformer-turns-ratio/.
Transformer Testing Reference, Transformer Turns Ratio (Oct. 24, 2026), https://www.transformertestingreference.com/tests/transformer-turns-ratio/.
@misc{etr-tests-transformer-turns-ratio,
title = {Transformer Turns Ratio},
howpublished = {\url{https://www.transformertestingreference.com/tests/transformer-turns-ratio/}},
organization = {Transformer Testing Reference},
publisher = {Transformer Testing Reference},
year = {2026},
note = {last substantive change 2026-10-24}
}{{cite web |title=Transformer Turns Ratio |website=Transformer Testing Reference |publisher=Transformer Testing Reference |url=https://www.transformertestingreference.com/tests/transformer-turns-ratio/ |date=2026-10-24 |access-date=}}