• Megger

Megger® TTR100 Series

Handheld Single Phase Turns Ratio Testers
Megger TTR100 Handheld turns ratio tester


  • Fully automatic, fast and easy-to-use
  • Robust and lightweight
  • Battery powered with power-saving and shutdown function
  • Tests turns ratio, phase displacement, excitation current, winding resistance and polarity
  • Meets all IP54 requirements
  • RS232 for data transfer and printing
  • Stores 200 test results and 100 userdefined transformer test settings
  • Six user-selectable languages


The Megger TTR100 is an automatic handheld, battery operated transformer turns ratio test set used to measure the turns ratio, excitation current, phase displacement, dc resistance and polarity of windings in single- and threephase distribution transformers (tested phase by phase), potential & current transformers, and tapped transformers. Deviations in the mentioned measurements will quickly indicate problems in transformer windings or in the magnetic core circuits.

The unique design of the TTR100 allows the user to operate the test set while holding it in one hand. No other transformer test set offers this capability. It effectively eliminates the user from having the kneel or bend down to operate the instrument and speeds up testing time. Realizing the extreme environments in which the TTR100 must operate, special attention has been paid to making it extra rugged, with a high impact, shock resistant case, yet incredibly lightweight at 3.3 lb. (1.5 kg). It weights less than any other commercially available instrument on the market.

Its rugged and robust design makes this instrument well suited for use in a variety of harsh environments. The TTR100 is particularly suited for testing in substations and transformer-manufacturing environments where testing single and three-phase transformers can be performed. The TTR100 provides reliable results, helping the user in determining the condition of the transformer under test. It features a high contrast LCD screen which can be seen in bright or ambient light.

The TTR100 comes equipped with specially designed leads which provide the necessary flexibility needed in all weather conditions.

This unit measures the highest turns ratio in the industry with an accuracy of 0.1% or better and with the lowest excitation voltage. No other instrument’s performance is comparable that is commercially available today. Another excellent feature of this TTR is the ability to accurately measure phase deviation (in minutes or centiradians) of the transformer primary versus secondary. This measurement is also useful in verifying phase errors in PTs and CTs.

The TTR100 features special software capabilities. It comes equipped with sufficient onboard memory to store up to 200 test results (including test report header information) in the field for later retrieval, as well as 100 user-defined transformer settings. Test results can be printed on an optional serial printer whenever a hard copy is desired, or the data can be downloaded to a PC. Identification of individual test readings is also easily done. The system software allows entry of the transformer alphanumeric serial number, transformer type and tap information (numerical, alphabetical, or alpha-numerical) for each test performed.

The TTR100 comes with a Windows® based software program that permits download of test data from the instrument to a PC database. Data stored in the database can be retrieved at a later date and test reports can be printed to assist in the preparation of management and/or analysis reports. These reports are easily transmitted via e-mail.

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  • The proper operation of a transformer relies almost entirely on the electrical properties of its windings. To ensure continued proper operation, transformers are tested to verify that their electrical properties have not changed from design specifications. A TTR is an extremely useful instrument for testing transformer windings because it can locate several types of problems within a single- or a three-phase transformer. It is also ideal to use for testing in meter shops for the inspection of CTs and PTs. It can determine the no-load accuracy of CTs and PTs and also determine the need to further test faulty CTs and PTs. The TTR100 applies voltage, with voltage ratio being directly proportional to turns ratio, to the high-voltage winding of a transformer and accurately measures the resulting voltage from the low voltage winding. In addition to turns ratio, the unit measures excitation current, phase angle deviation between the high and low voltage windings, percent ratio error, dc winding resistance and polarity.


  • Faster, easier handheld operation. User no longer has to kneel or bend down to operate the instrument.
  • Powered by rechargeable battery, provides up to fifteen hours of field operation.
  • Report header information such as company name, substation name, transformer manufacturer, transformer ratio, operator, temperature and %RH can be entered and saved via the alphanumeric keypad.
  • Measures the widest turns ratio range in the industry (20,000:1) with the highest accuracy (±0.1%, 0.8 to 2000) at a low excitation voltage.
  • Enables the operator to enter the ratio of the transformer and all of its taps. This allows the operator to know immediately when a tap is outside the acceptable limits so that problem taps can be easily identified.
  • Records ratio errors for bushing CTs to an accuracy of ±0.1% nameplate. This reduces the need for additional test equipment and improves set-up time.
  • Measures the phase deviation (in minutes, degrees or centiradians) of the transformer primary versus secondary. This quickly indicates problems in the transformer such as partial shorted turns and core faults. This measurement is also useful in verifying phase errors in all types of PTs and CTs.
  • Perfect for meter shops, the TTR100 can be used for inspection purposes by using it to determine the no-load accuracy of most CTs and PTs. It also can be used to determine the need to further test potentially faulty CTs and PTs.
  • The TTR100 is ideal for use by transformer manufacturers. Its unique testing procedures and storage capability allows an operator to set up and test single and three-phase transformers (with multiple tap changers and bushing CTs) in minimal time.
  • A “Quick Test” mode provides a fast determination of the turns ratio, excitation current, phase angle deviation, and winding resistance in single- and three-phase transformers and CTs. In addition, polarity is provided for CTs and single-phase transformers.
  • Displays all measured and calculated values for each test including ratio, excitation current, ratio error, phase angle deviation, transformer vector group, winding resistance and polarity thus providing comprehensive and conclusive data.
  • Literature
  • Specifications
Excitation Voltage: 8 V rms for testing distribution or power transformers, PTs; 1.5 V ac RMS, or 8 V ac RMS for testing CTs. The excitation voltage is switched automatically if excitation current exceeds a preset value.
Test Frequency: 55 Hz internally generated providing a universal 50/60 Hz test set
Excitation Current Range: 0 to 100 mA, 4-digit resolution
Turns Ratio Range : 8 Vac: 0.8 to 20,000, 5 digit resolution (for transformers and PT testing) 1.5 V ac: 5.0 to 2200, 5 digit resolution (for CT testing)
Phase Deviation Range : ±90º, 1 decimal point for the minutes display, 2 decimal points for the degree display, or for the centiradian display
Winding Resistance Ranger: 0 to 2000 Ω, 4 digit resolution
Transformer Vector Group: 1PH0 or 1PH6
Current (rms) accuracy:
±(2% of reading + 1 digit)
Turns Ratio Accuracy :

±0.1% (0.8 to 2000)

±0.15% (2001 to 4000) ±0.20% (4001 to 10,000) ±0.25% (10,001 to 20.000)
Winding Resistance Accuracy: ±(10% of reading + 1 digit) for 10 Ω to 2000 Ω range ±(10% ±1 mΩ) for 10 mΩ to 9.99 Ω range ±(10% ±0.5 mΩ) for 0.1 mΩ to 9.99 mΩ range
Display full graphics : LCD module, wide temperature range, 128 x 64 dots (21 characters by 8 lines)
PC/Printer Interface:
RS232C port, 9-pin, 57.6 Kbaud (19.2 Kbaud for the printer)