Transformer Turn Ratio Tester

A) Hand held TTR

  • Tests turns ratio, phase displacement, excitation current, vector group, winding resistance and polarity.
  •  Fully automatic; fast; easy-to-use; handheld; robust; lightweight.
  •  Battery powered with power-saving and shutdown function.
  •  Alphanumeric keyboard.
  •  RS232 for data transfer and printing.
  •  Stores 200 test results and 100 user-defined transformer test settings.

The latest Transformer Testing Equipment TTR available from Megger is the TTR100, a handheld, robust, lightweight and battery operated instrument. This TTR will complement several existing Megger transformer test products and will offer functions, such as winding resistance and polarity. These functions, as well as the phase angle measurement function, can be switched off when not required.

With a turn ratio of 20,000:1, the TTR100 offers the highest turns ratio accuracy in the industry of 0.1%. The TTR100 features special software capabilities.

The TTR100 is used to perform final test and calibration of transformers in the manufacturing process, such as a QA or Test Department. Using the new TTR100 in this environment will improve the productivity of such QA testing, as well as efficiently collect and store large amounts of data, which can be uploaded to a PC spreadsheet, or database program.

  •   Fully automatic; fast; easy-to-use; robust; lightweight.
  •   Battery powered.
  •   Tests turns ratio, excitation current, and polarity.
  •   Simple, one-button operation.
  •   Quick-start guide on front panel.
  •   Operator-selectable languages.

The Megger Transformer Testing Equipment TTR25 is an automatic hand-held battery operated transformer turns ratio test set.

It is used to measure the turns ratio, excitation current and polarity of windings in single- and three-phase distribution and power transformers (tested phase by phase), potential & current transformers, and tapped transformers.

The unique design of the TTR25 allows the user to operate the test set while holding it in one hand. It effectively eliminates the user from having to kneel or bend down to operate the instrument and speeds up testing time.

Realizing the extreme environments in which the TTR25 must operate, special attention has been paid to making it extra rugged, with a high impact, shock resistant case, yet incredibly lightweight at a mere 870 g (1.9 lbs).

  •  Simple, one-button operation.
  •  Lightweight, handheld.
  •  Battery powered.
  •  Battery powered (AA or LR-6).
  •  Tests turns ratio, excitation current, and polarity.
  •  Ability to record via optional printer.

The Megger Transformer Testing Equipment TTR20 is an automatic, hand-held, battery operated transformer turns ratio test set.


B) Hand cranked TTR

  •  Used for testing single phase power and distribution transformers.
  •  Design based on precision bridge measuring technique.
  •  Unmatched accuracy (±0.1%) in a portable design.

The Single Phase Transformer Testing Equipment TTR, Transformer Turns Ratio Test Set, measures the turns ratio and exciting current of windings in power, potential and current transformers. Deviations in turns ratio readings indicate problems in one or both windings or the magnetic core circuit.

The TTR test set aids in identifying:

  •  Shorted coils.
  •  Open circuits.
  •  Incorrect connections.
  •  Internal faults or tap-changer defects in step regulators as well as in transformers.

The instrument measures highly sensitive turns ratios of up to 129.99:1 with accuracy of ±0.1%. An optional auxilary transformer extends the ratio range to 329.99:1.

The TTR set operates on the principle that the voltage ratio of the transformer at no load is practically equal to the true turns ratio.

The major source of error in a transformer is a primary impedance drop due to magnetizing current, which is kept to a minimum by excitation at a fraction of rated voltage. By employing a design that meets both of these conditions along with the use of a null balance system, the turns ratio of a transformer can be determined accurately.

When measuring the turns ratio of distribution and power transformers, the accuracy is well within 0.1%.

  •   Stand-alone or remote-control operation.
  •   Accurately measures ratio, phase deviation and excitation current.
  •   Field upgradeable without compromise to calibration.
  •   Built-in capability for storing and downloading test results in an XML format, via RS-232, Ethernet or USB ports (depending on model).
  •   Works in the presence of high interference/high voltage.
  •   Highest ratio measurement (45,000:1); highest accuracy (0.1%).
  •   Displays % error vs. name plate with pass/fail limits.

The Transformer Testing Equipment TTR300 Series of three-phase transformer turns ratio test sets are designed to measure the turns ratio of power, instrument, and distribution transformers in a substation or manufacturing environment. A rugged and robust design makes these instruments well suited for use in a variety of harsh environments. Our leads are specially designed to provide the necessary flexibility needed in cold weather.

The Transformer Testing Equipment TTR300 Series are ideal for use by power transformer manufacturers. Their unique testing procedures and storage capability allows an operator to set up and test difficult three-phase transformers (with multiple tap changers and bushing CTs) in a fraction of the time than it used to take with other TTRs. This test also includes a pass/fail limit of individual ratios.

  •   Guaranteed accuracy ±0.05% from -20°C to +50°C.
  •   3Ø test voltage – up to 250V.
  •  3Ø step up ratio (patent pending)
  •  Phase shifting & zig-zag transformers tested easily and accurately.
  •   Smallest/lightest 3Ø test set on the market.
  •   Fast 3Ø tests – less than 10 second.

The NEW Megger TTRU3 transformer turns ratio meter uses a revolutionary design to perform a complete series of measurements on a transformer, including 3Ø step up turns ratio testing (patent pending). 3Ø voltage output offers numerous advantages to testing with today’s busy schedules.

The TTRU3 is an important tool for determining the mechanical condition of transformers. All ratio tests are performed in one instrument, with only one 3Ø lead-set connection. The TTRU3 utilizes the latest 7 in. (180 mm) color touch display, as well as an optional printer so results are never lost. This is complimented with remote control which can be operated from a PC, as well as the ability to download results to a USB memory device.


Transformer winding resistance meter

A) Single Phase – MTO 210

  • Direct 2-channel digital reading (1 µΩ to 2000 Ω).
  •  DC test current up to 10 A maximum.
  •  0.25% measurement accuracy.
  •  Integrated demagnetization feature.
  •  Tests operation of on-load tap-changers.
  •  Very fast auto safety discharge circuit.

The Transformer Testing Equipment MTO210 transformer ohmmeter is a line-operated, field-portable instrument designed specifically to measure the dc resistance of all types of magnetic windings safely and accurately. It can test transformers and rotating machine windings and perform low-current resistance measurements on connections, contacts and control circuits.

The Transformer Ohmmeter is extremely useful when testing the windings and contact resistance of tap-changers with “make-before-break” contacts and voltage regulators. This action will check for pitted or misaligned contacts as the instrument will give an indication if either condition occurs.

B) Three phase

  • Automated 8-terminal/6-winding measurement capability.
  •  Simultaneous winding magnetization.
  •  Tests operation of on-load tap-changers.
  •  Built-in auto-demagnetization feature.
  •  Automatic discharge.
  •  Power DB software (MTO330).

The Transformer Testing Equipment MTO 300 series delivers full eight-terminal/six-winding resistance measurement capability. It is designed to save time for the user by testing all normal 6 windings without having to disconnect and reconnect leads during testing.

The Transformer Testing Equipment MTO3xx series also shares the Megger TTR300 series lead set. Users who test both turns ratio and winding resistance can save time and money since only one lead set is needed to connect to the transformer.

  •   Capable of testing transformers up to 1000 MVA.
  •   DC test current up to 50 A maximum.
  •   Integrated demagnetization feature.
  •   Computer control and internal data storage.
  •   Validates proper operation of on-load tap-changers.
  •   Protected against accidental current lead disconnection (through potential leads).

The Transformer Testing Equipment MTO250 Transformer Ohmmeter is a line-operated, field- portable instrument designed specifically to measure the resistance of all types of magnetic windings safely and accurately. It tests transformers, shunt reactors, rotating machine windings and performs low resistance measurements on connections, contacts and control circuits.

The dual set of potential inputs enables the resistance measurement of either two primary, two secondary windings, or of a primary plus a secondary winding simultaneously. This dual reading, dual injection characteristic, is a highly efficient method of completing tests in a timely manner.



A) MWA300 and MWA330A

  • Combines TTR and resistance testing in one box – faster, more efficient testing.
  •   55% smaller, 40% lighter than individual instruments.
  •  Only one set of leads required – lighter, smaller and less expensive.
  •  Built-in auto-demagnetization feature.
  •  One test form – easier, faster to complete.
  •  PBuilt-in demagnetisation.

The Megger MWA300 and 330A Transformer Winding Analysers are here to offer you a faster, more efficient testing device through combining TTR and resistance testing in a single unit.

This advanced 3-phase transformer test system provides complete ratio, phase and winding resistance measurements with only one 3-phase lead-set connection. What’s more, it offers portability, a reduced set-up time and increased job safety.

Once connected, the MWA300 performs DC resistance measurements on all high- and low-side windings without reconnection. It has an 8-terminal/6-winding resistance measurement capability and doesn’t need any inter-connected boxes, allowing you to test all 6 windings without having to disconnect and reconnect leads.
The MWA300 series saves you even more time by using a single software platform, PowerDB, which means you only need one set-up and one easy-to-use test form.

The MWA300 series can be used effectively test power transformers, distribution transformers, CTs and VTs, and motors and generators.

The following tests are easily performed with a single instrument, the MWA300 series, and a single 3-phase lead set connection:
•   3-phase turns ratio
•   3-phase winding resistance
•   OLTC continuity (make-before-break)
•   3 phase core demagnetization
•   Magnetic balance / flux distribution
•   Excitation current
•   Polarity and phase angle deviation
•   Auto vector detection
•   Heat-run test
The MWA330A comes equipped with a built-in computer that has a 305 mm (12 in) colour display and touch-screen interface. The computer is designed to control the unit and it can store up to 100, 000 data sets.

The Transformer Testing Equipment MTO3xx series also shares the Megger TTR300 series lead set. Users who test both turns ratio and winding resistance can save time and money since only one lead set is needed to connect to the transformer.