Transformers Testing TTRT 03

Transformers Testing TTRT 03

The TTRT-03 is Amperis’ second generation, microprocessor-based, automatic, three phase, and transformer turns-ratio tester. This lightweight, portable unit is designed for testing transformers at utility power substations. The TTRT-03 determines the transformer turns-ratio using the IEEE C57.12.90 measurement method. The transformer turns-ratio (ranging from 0.8 to 15,000) is determined by precisely measuring the voltages across the unloaded transformer windings. To ensure accuracy, the TTRT-03’s measuring circuitry self-calibrates before each measurement. It requires neither adjustment nor temperature compensation. The TTRT-03’s turns-ratio measurement accuracy is 0.1% or better.

The TTRT-03 can perform a specific test for each transformer type (such as single phase, delta to Y, Y to delta, delta to delta, or Y to Y) without the need to switch test hookup cables. Also, the unit’s automatic transformer phase detection feature can detect different transformer vector diagrams. The TTRT-03 can automatically detect and test 67 transformer types defined by ANSI, CEI/IEC and Australian standards. To prevent an accidental wrong test-lead hook-up (e.g., when the operator reverses H and X leads), the TTRT-03 outputs a low-level test voltage to verify the hook-up condition before applying the full test voltage to the transformer. In addition to measuring a transformer’s turns-ratio, the TTRT-03 can also measure a transformer’s excitation current (in milli-amperes) and its winding phase angle. Three test voltages (8 Vac, 40 Vac, 100 Vac) allow the TTRT-03 to test CT’s and PT’s, as well as power transformers. The TTRT-03 can also calculate the turns-ratio percentage error if the transformer’s nameplate voltages are provided. The baseline turns-ratio is calculated using the nameplate voltages, and the test results are compared to the baseline turns-ratio. The percentage error is then calculated from the difference between the baseline and test turns-ratios.

User Interface

The TTRT-03 features a back-lit LCD screen (20 characters by 4 lines) that is viewable in both bright sunlight and low-light levels. The test results screen displays the transformer turns ratio, excitation current, and turns-ratio accuracy. The unit is controlled via a rugged, 16-key, membrane keypad.

Computer Interface

The TTRT-03 can be computer-controlled via the RS-232C interface using the supplied PC software. The Windows®-based software can be used to run a test and to store test results on a PC. Test results can also be exported to Excel, PDF, and XML formats for further analysis.

Transformer Load Tap Changer Control

Voltage regulator or LTC tap positions can be changed remotely using the optional Tap-Changer Remote Control Box. This option eliminates the need to manually raise or lower tap positions from the transformer control panel.

Built-in Thermal Printer

The TTRT-03 features a convenient built-in 4.5-inch wide thermal printer that can be used to print test results.

Internal Test Record Storage

Up to 200 test records can be stored in the TTRT-03’s Flash EEPROM memory. Each test record may contain up to 99 turns-ratio, excitation current, phase angle, and nameplate voltage readings. Test records can be recalled locally or transferred to a PC via the RS-232C interface.

Transformer Test Plans

The TTRT-03 can store up to 128 transformer test-plans in its Flash EEPROM. A test plan is comprised of the transformer nameplate voltages for each tap setting. The calculated turnsratio based on the nameplate voltages is compared with the measured turns-ratio to derive the percentage error and Pass/Fail results. By using a test plan, a transformer can be quickly tested and turns-ratio Pass/Fail reports can be reviewed. Test plans can be created with the included PC software and can be transferred to the TTRT-03 via the RS-232C interface.

TTRT-03’s Specifications


Portable, automatic, three-phase transformer turns-ratio meter

Physical specifications

17”W x 7”H x 13” D (43.2 cm x 17.8 cm x 33.0 cm); Weight: 14 lbs (6.4 kg)

Input power

3 amps, 100 - 120 Vac or 200 - 240 Vac (selectable), 50/60 Hz

Measurement method

ANSI/IEEE C57.12.90

Ratio measuring range

0.8 - 15,000 (5-digit resolution)

Turns ratio accuracy

0.8 - 1999: ±0.1%, 2,000 - 3,999: ±0.25%, 4,000 - 15,000: ±1% @ 8 Vac
0.8 - 1999: ±0.1%, 2,000 - 3,999: ±0.20%, 4,000 - 15,000: ±1% @ 40 Vac
0.8 - 1999: ±0.1%, 2,000 - 3,999: ±0.15%, 4,000 - 15,000: ±1% @ 100 Vac

Test voltages

8 Vac @ 1 amp, 40 Vac @ 0.6 amp, 100 Vac @ 0.1 amp

Excitation current reading range

0 - 2 Amperes; Accuracy: ±1mA, ±2% of reading (±1 digit)

Phase angle measure

0 - 360 degrees; Accuracy: ±0.2 degrees ( ±1 digit)


Back-lit LCD screen (20 Characters by 4 Lines); Viewable in bright sunlight and low-light levels


Built-in 4.5-inch wide thermal printer

Computer interface

One RS-232C port

Pc software

Windows®-based Transformer Turns-Ratio Analyzer application is included

Internal test record storage

Stores 200 complete transformer test records. Each test record includes nameplate voltage, winding turns-ratios, excitation current, and winding phase angle

Internal test planstorage

Stores up to 128 transformer test plans


UL Certified (UL 61010A-1), CAN/CSA Certified (C22.2 No. 1010.1-92)


Operating: -10°C to +50°C (+15°F to +122°F); Storage: -30°C to +70°C (-22°F to +158°F)


90% RH @ 40°C (104°F) non-condensing


2,000 m (6,562 ft) to full safety specifications


One 15-foot single-phase cable set, one 15-foot 3-phase cable set, one 25-foot extension cable set, one rs-232c cable, cable carrying bag

Optional accessories

Transportation case, transformer load tap-changer remote control device


1 year on parts and labor

NOTE:the above specifications are valid at nominal voltage and ambient temperature of +25°C (+77°F). Specifications are subject to change without notice

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