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Transformer Turns Ratio Testers

About Transformer Turns Ratio Testers

Transformer turns ratio testers from the TRT series are DV Power instruments mainly designed for the measurement of power transformer turns ratio. Also, they measure transformer excitation current and phase shift. Special tests, such as automatic vector group detection and magnetic balance, can be performed on three-phase transformers and three-phase autotransformers.

All models, except TRT03 and TRT-H series, have a built-in true three-phase power source, which is necessary for testing the turns ratio of transformers with special configurations, such as phase-shifting, rectifier, arc-furnace, traction transformers, etc.

DV Power turns ratio testers can output various test voltages for different applications. From the extremely low test voltage of 1 V AC that enables turns ratio verification of the majority of current transformers, up to the highest test voltage of 500 V AC that provides the most accurate turns ratio testing of power transformers used in power generation and transmission. By using the external booster, the test voltage increases up to 5 kV AC in order to successfully test capacitive voltage transformers.

All DV Power turns ratio testers, except the TRT-H series, have a built-in tap changer control unit. Because of that, it is possible to control the on-load tap changer (OLTC) directly from the device. In order to make the most out of this feature, the instrument and included DV-TR software can be programmed to do everything automatically – running turns ratio tests, changing OLTC tap positions, and saving results. This option significantly facilitates and shortens the turns ratio testing time.

TRT turns ratio testers, except the TRT-H series, use the same set of cables as three-phase winding ohmmeter & tap changer analyzers from the TWA series.  Consequently, it enables a one-time cable setup for performing eight tests:

  • turns ratio
  • excitation current
  • phase angle
  • magnetic balance
  • vector group detection
  • winding resistance
  • on-load tap changer DVtest
  • and demagnetization.

Series Comparison

Maximum Test Voltage
Test Voltage Source
TRT500, TRT400, TRT250, TRT100
Portable / Rack
500 V, 430 V AC, 250 V AC, 170 V AC (depending on model)
Single-Phase & True Three-Phase
Touch Screen 10.1'' or 7'' (depending on model)
Transformer Turns Ratio Tester TRT Standard Series
TRT63, TRT33, TRT03
Portable / Rack
250 V AC, 100 V AC (depending on model)
Single-Phase & True Three-Phase (depending on model)
Handheld Turns Ratio Tester Isometric View TRT-H
40 V AC