Turns ratio and deviation
Compare measured voltage relationship with the expected or entered value across the required phases and taps.
- sales@hvtesters.com
- +8613661908522
- sales@hvtesters.com
- +8613661908522
Ratio evidence without guesswork
Transformer Ratio Test Equipment
Compare TTR testers for turns ratio, ratio deviation, phase angle, vector group and tap-position checks. Select around the transformer connection, field workflow and records your team must produce—not a model name alone.
Ratio range to 10000Three-phase and portable routesTap-by-tap reporting
TTR result map
Ratio0.9–10000Match the expected transformer ratio
Angle0–360°Check phase displacement
Group0–11Recognize vector relationship
TapPositionedPreserve results by tap
Turn nameplate data into a controlled test planConfirm the exact transformer type, connection, phases, tap sequence and report fields before selecting equipment.
Four outputs, one equipment decision
Specify what the tester must calculate, recognize and record
A wide ratio range is useful, but it is not the whole specification. Procurement should begin with the transformer design and the evidence required by the approved test procedure.
Phase angle
Choose angle measurement when the connection relationship or phase-shifting design makes displacement part of the decision.
Vector group
Automatic group recognition can reduce manual interpretation for three-phase and selected special transformer configurations.
Tap-position record
Plan a repeatable sequence so every result remains attached to the correct tap, phase, connection and transformer identity.
Current Wrindu TTR routes
Compare a three-phase analysis route with a battery-powered field route
Both products publish a ratio range of 0.9–10000. Their strongest differences appear in transformer coverage, angle functions, power arrangement and field operating style.
Three-phase / special transformers
RDB-III
Transformer Ratio Tester
For ratio, angle and automatic vector-group work where three-phase output and broader special-transformer coverage matter.
0.9–10000Published ratio range
0–360°Published angle range
±0.2°Published angle accuracy
0–11Automatic vector groups
Portable / battery field work
RDB-IIHX
Portable Turn Ratio Tester
For compact field work requiring automatic ratio and group tests, sunlight-readable display, rechargeable power and portable records.
0.9–10000Published ratio range
>8 hoursPublished use time
5.6-inchHigh-brightness display
USB / RS232Published interfaces
Model-selection note: published specifications support initial comparison, not final acceptance. Confirm the current model version, transformer connection, required test voltage, angle function, accessories, language and formal data-report requirement with Wrindu before ordering.
Choose by operating route
The same ratio range can serve very different transformer workflows
Three-phase ratio and group verification
Prioritize automatic vector-group recognition, angle measurement and efficient phase handling.
- Power and distribution transformers
- Entered nameplate and tap data
- Ratio deviation by phase and position
Portable substation and service work
Prioritize battery endurance, readable display, compact transport and practical data transfer.
- Multiple assets in one visit
- Limited access to mains power
- On-site storage or optional printing
Special transformer comparison
Confirm the tester and test method support the exact winding arrangement before relying on automatic recognition.
- Z-type and phase-shifting designs
- Rectifier or grounding transformers
- Unknown or nonstandard connections
Product comparison matrix
Match the published capability to the transformer and site constraint
Use this matrix for an early shortlist. Request the current technical sheet and confirm the final configuration before procurement.
| Selection field | RDB-III | RDB-IIHX | Why it matters |
|---|---|---|---|
| Published ratio range | 0.9–10000 | 0.9–10000 | Must cover expected ratios with suitable accuracy and resolution across the working band. |
| Angle / vector information | 0–360°; ±0.2° angle accuracy; groups 0–11 | Automatic ratio and group measurement; confirm required angle output | Separates a basic ratio check from connection and phase-displacement evidence. |
| Transformer coverage | Conventional and multiple special transformer types published | Conventional, Z-type, PT samples; CT ratio and polarity also published | Automatic functions are useful only when the exact winding design is supported. |
| Power arrangement | Confirm current AC supply configuration | Rechargeable lithium battery and adaptive AC charger | Battery operation can improve mobility where dependable mains power is unavailable. |
| Field interface | Automatic calculation and product-specific data functions | 5.6-inch high-brightness LCD; USB and RS232; optional external printer | Screen readability and report transfer affect throughput across many taps and assets. |
| Best starting route | Three-phase / special-transformer analysis | Portable field ratio and group work | Final selection still depends on transformer drawings, procedure and required report fields. |
Tap-by-tap evidence workflow
Build the test record before choosing the instrument
Define the transformer
Collect rated HV/LV values, phases, vector diagram, tap range, tap step and special winding information.
Define the output
State whether the approved procedure requires ratio, deviation, polarity, angle, vector group, current or another result.
Map every tap
Prepare the tap sequence, phase labels, connection plan, lead access and criteria for retesting an unexpected value.
Preserve traceability
Store asset identity, tap, phase, test configuration, raw reading, calculated result, operator and review status.
Interpret within the right boundary
A TTR result is configuration evidence—not a complete winding diagnosis
Use ratio evidence with the transformer diagram, tap position and other tests
A ratio tester can reveal an unexpected voltage relationship, connection, group or tap result. It does not replace DC winding-resistance measurement, insulation assessment, SFRA or the project authority's diagnostic process. An unexpected result should first trigger controlled checks of identity, test leads, connection, phase labels, tap position and entered nameplate data.
Prepare a useful inquiry
Send enough information to compare the right TTR configuration
Transformer and method
- Transformer type, rated power and rated HV/LV voltages
- Single-phase or three-phase configuration and vector diagram
- Tap changer type, number of positions and tap step
- Special winding, phase-shifting or rectifier configuration
- Required test standard, owner procedure or FAT/field method
Equipment and deliverables
- Required ratio, angle, group, polarity and current outputs
- Expected ratio range and preferred excitation/test-voltage options
- Battery or site-power requirement and expected daily workload
- Lead lengths, clamps, cases, printer, USB and software needs
- Report template, language, calibration documents and delivery schedule
Transformer ratio tester FAQ
Questions to settle before ordering TTR equipment
What does transformer ratio test equipment measure?
Transformer ratio test equipment applies a controlled low test voltage and evaluates the voltage relationship between windings. Depending on the model, it may calculate turns ratio, ratio deviation, phase angle, vector group, polarity, tap position and excitation current. Confirm the exact outputs required by the approved test procedure.
How do RDB-III and RDB-IIHX differ?
Both publish a ratio range of 0.9–10000. RDB-III is positioned for three-phase ratio, angle and automatic vector-group work across conventional and selected special transformers. RDB-IIHX emphasizes portable battery-powered field testing, a high-brightness screen, automatic ratio/group measurement, USB/RS232 interfaces and CT ratio/polarity capability. The transformer design and report requirement determine the better fit.
Is the widest ratio range enough to choose a TTR tester?
No. Buyers should also compare accuracy by ratio band, resolution, supported connections, angle and vector-group functions, test-voltage options, tap workflow, lead arrangement, power supply, screen visibility, protection, storage and report export. A range that covers the asset does not prove every required function is available.
Can a transformer ratio tester replace a winding resistance tester?
No. A TTR tester evaluates voltage ratio and connection relationships using an AC test signal. A winding resistance tester measures DC resistance and has different test-current, stabilization and discharge requirements. The measurements can support the same investigation but answer different technical questions.
What information should be sent with a TTR equipment inquiry?
Send the transformer nameplate and vector diagram, rated voltages and power, phase configuration, tap range and positions, special winding information, expected ratio range, required measurements, approved procedure, site-power conditions, lead length, data/report format, calibration documents and delivery schedule.
Compare transformer ratio testers against your actual transformer
Send Wrindu the nameplate, vector diagram, tap arrangement, required measurements and reporting workflow. The technical team can help compare the RDB-III, RDB-IIHX and suitable accessories.
Technical parameters shown here are based on public HVTesters product information reviewed on 26 August 2026. Confirm the current model, specification, accessories, calibration documents and approved test method before purchase or use.
Technical selection guide
Know More About Transformer Ratio Test Equipment
Open this guide when you need to turn a transformer nameplate, vector diagram and tap schedule into a practical TTR tester specification.
Know More: Ratio Range, Vector Group, Tap Workflow and Field Reportingnameplate · connection · measurement · traceability
What makes transformer ratio test equipment a separate procurement category?
A transformer ratio tester—often called a turns ratio tester, TTR tester or transformer ratio meter—evaluates the voltage relationship between transformer windings using a controlled low-voltage AC test signal. The resulting ratio is compared with the expected relationship derived from the transformer design, nameplate and selected tap. Many modern instruments also provide ratio deviation, phase angle, vector-group recognition, polarity and excitation-current information.
This is narrower than the intent of the power transformer testing equipment parent page. That parent must help a buyer navigate winding resistance, insulation, tan delta, SFRA, OLTC, oil and other instrument groups. The ratio page has a different job: it helps a buyer compare TTR equipment after the need for ratio and connection verification has already been established.
Electrical relationship
Determine whether the measured HV/LV relationship agrees with the expected turns or voltage ratio for the selected tap.
Connection evidence
Use phase angle, polarity and vector-group functions when the connection relationship forms part of the required record.
Tap traceability
Keep each reading tied to the correct tap, phase, transformer identity, connection and test configuration.
Start with transformer documents, not a tester specification sheet
The safest shortlist begins with the transformer rather than the instrument. Ask for the nameplate, vector diagram, rated high- and low-voltage values, phase configuration, rated power, tap changer type, number of tap positions, nominal tap, tap step and any special winding information. These fields reveal whether the project needs only a straightforward ratio comparison or also needs angle, polarity, automatic vector recognition and support for an unusual connection.
The expected ratio may not always be a single fixed number. A tapped transformer has a planned relationship at each tap. Three-phase transformers also require correct phase correspondence and interpretation of the specified vector group. Phase-shifting, rectifier, grounding, Z-type, Scott or other special arrangements may require functions and connection methods beyond those used for a conventional distribution transformer.
Procurement boundary: never treat “0.9–10000” as proof that a tester supports every transformer within that numeric band. Range, connection support, test voltage, phase handling, angle function, software logic and the approved test method all matter.
How to read the major TTR equipment selection fields
| Selection field | Question to ask | Common mistake | Evidence to request |
|---|---|---|---|
| Ratio range | Does the expected ratio at every required tap fall within the supported band? | Checking only the nominal ratio and ignoring extreme taps or a special winding. | Range plus accuracy and resolution by ratio band. |
| Test / excitation voltage | Which selectable or automatic output is appropriate for the transformer and method? | Assuming a higher number is always better without considering current, burden or induced response. | Available outputs, current limits and model-specific application guidance. |
| Phase angle | Is numerical angle output required for the connection or phase-shifting design? | Buying a basic ratio instrument when angle forms part of the acceptance record. | Angle range, resolution, accuracy and supported connection types. |
| Vector group | Can the device recognize or verify the specified group and unknown connections? | Assuming every automatic group mode supports every special transformer. | Published group function and a written confirmation for the exact winding arrangement. |
| Tap workflow | How are expected values, tap positions and results entered, stored and exported? | Recording readings without a reliable link to tap and phase. | Example screen flow, memory structure and sample report. |
| Power and portability | Will work occur near dependable AC power or across multiple field assets? | Selecting battery equipment without checking endurance, charging or cold-weather expectations. | Power input, battery use time, charger, transport case and environmental limits. |
RDB-III and RDB-IIHX answer different operating priorities
RDB-III: three-phase, angle and special-transformer route
The RDB-III Transformer Ratio Tester publishes a ratio range of 0.9–10000 and an angle range of 0–360°. The published angle accuracy is ±0.2°, with minimum ratio resolution of 0.0001 and angle resolution of 0.01°. Its three-phase output, automatic vector-group recognition from 0 to 11 and stated support for multiple special transformer types make it a logical route when the project needs more than a basic portable ratio reading.
The buyer should still confirm the exact model version, supported connection, required output voltage, lead set, report method and procedure. Special-transformer compatibility is not a substitute for reviewing the actual vector diagram. The sales inquiry should name the transformer design rather than using the broad phrase “special transformer.”
RDB-IIHX: portable, battery-powered field route
The RDB-IIHX Portable Transformer Turn Ratio Tester also publishes a ratio range of 0.9–10000. Its positioning emphasizes a compact handheld format, rechargeable lithium power, more than eight hours of published use time, a 5.6-inch high-brightness display, USB and RS232 interfaces and an optional external printer. It automatically performs ratio and group tests without requiring the operator to know the HV/LV connection method in advance.
RDB-IIHX also publishes CT ratio and polarity capability. That extra function does not turn this ratio landing page into a CT/PT analyzer page. A complete instrument-transformer analyzer may need excitation, burden, knee-point, secondary resistance and other dedicated functions. Buyers whose primary objective is CT or PT evaluation should define those measurements separately.
Build a tap schedule that survives review
Ratio equipment can generate many readings quickly, but speed does not create traceability by itself. The test team should know the transformer identity, phase, test connection and tap position for every record. A useful pre-test worksheet lists the expected value at each tap, the allowed comparison method from the approved procedure, the actual reading, calculated deviation, status and any retest note.
Freeze the asset identity
Use serial number, bay or asset ID, rated voltage, vector group and selected winding designation.
Map the connection
Record which terminals and phases are connected, lead orientation and the instrument mode used.
Sequence the taps
List the start position, direction of movement and required results before changing the tap.
Control unexpected values
Define when to stop, inspect leads, confirm tap position, repeat the test or escalate for review.
Preserve raw and calculated data
Keep the measured ratio as well as any deviation, angle, group, current and status generated by the instrument.
Export with context
Make sure a USB file, printout or software report still identifies asset, tap, phase, configuration and operator.
Do not diagnose a transformer from one ratio value alone
An unexpected ratio or vector result can have several explanations: incorrect entered nameplate data, swapped leads, wrong terminal identification, an unintended tap position, a connection issue, an unsupported automatic mode or a transformer condition that needs further investigation. The first response should follow the approved procedure and verify controllable test conditions before making a technical conclusion.
A ratio tester and a transformer winding test equipment page belong near each other in the site architecture because both concern winding evidence, but they do not own the same search intent. TTR equipment uses an AC test signal to evaluate the voltage relationship and connection. A DC winding resistance tester evaluates resistance, requiring appropriate current, stabilization, temperature treatment and safe discharge. SFRA, insulation, tan delta and oil tests answer still other questions.
Likewise, ratio measurements appear in several lifecycle stages without making the pages interchangeable. The transformer commissioning equipment page organizes the full pre-energization scope. The transformer maintenance equipment page organizes periodic and condition-driven work on operating assets. This page remains the commercial comparison page for the ratio instrument group.
Questions a procurement team should settle with the manufacturer
- Which exact transformer types and connection groups are supported by the selected model and software version?
- What ratio accuracy and resolution apply within the project's expected ratio band?
- Does the required angle, polarity, vector-group, tap or excitation-current result appear in the stored and exported record?
- Which output or test-voltage options are available, and how are they selected for different transformers?
- Can the tester handle unknown connections, and what restrictions apply to special transformers?
- How are expected ratios and tap positions entered, and can a sample tap-by-tap report be reviewed before purchase?
- What leads, clamps, extension options, printer, cases, chargers and country-specific power accessories are included?
- What local storage, USB, RS232, application or PC software functions are supplied?
- Which calibration document, factory test record, manual language and remote training options can be supplied?
- What current product revision will be delivered, and which published specifications should be referenced in the purchase order?
A practical inquiry template
A concise but technically useful inquiry might read: “We need transformer ratio test equipment for three-phase power transformers with the attached nameplates and vector diagrams. The tap range is ___ to ___ with ___ positions. Our procedure requires ratio, deviation, phase angle and vector-group results at every tap. Field power is ___, the longest required test lead is ___, and the report must include asset ID, phase, tap position and raw result. Please compare RDB-III and RDB-IIHX, confirm supported connections and supply current specifications, accessories, calibration documents and sample reports.”
This format gives Wrindu enough information to discuss measurement fit, workflow and accessories without assuming that the same configuration is suitable for every transformer. Final acceptance criteria and test interpretation remain with the project authority and applicable procedure.
Need a model comparison based on your transformer?Send the nameplate, vector diagram, tap schedule and required report fields.
Contact Wrindu