Tap Changer Analyzer & Winding Ohmmeter RMO40TT



  • On-load tap changer dynamic resistance measurement
  • Three resistance measurement channels
  • Four temperature measurement channels
  • Automatic resistance/temperature measurement for the Heat Run test
  • Rapid automatic demagnetization
  • Vibration measurement
  • Tap changer motor current monitoring channel
  • Automatic discharge circuit
  • Built-in tap changer control unit
  • Detailed analysis of test results using DV-Win software

The Tap Changer Analyzer & Winding Ohmmeter RMO40TT instrument is designed for winding resistance measurement of inductive objects, and for a tap changer analysis. The RMO40TT instrument is based on the state of the art technology, using the most advanced switch mode technology available today. The RMO40TT instrument is accurate (0,1%), powerful (up to 40 A) and lightweight. It generates a true DC ripple free current with automatically regulated measurement and discharging circuit.

The RMO40TT instrument can perform a simple, quick and reliable transformer on-load tap changer condition assessment. This instrument enables measurements of a winding resistance in every tap position, current ripple values (percentage of a current drop during a tap change) and transition times during the tap changes. Problems with a connection, contacts, and selector/diverter switch operation (tap change with interruption) can be detected with these measurements.

The RMO40TT instrument provides temperature measurement for the Heat Run test by using four dedicated temperature channels. It enables obtaining the Hot Spot temperature along with temperature and resistance graphs which represent the cooling process.


Included accessories

  • DV-Win PC software including    USB cable
  • Built-in Tap Changer Control Unit
  • Tap Changer Control cable
       5 m (16.4 ft)
  • Mains Power cable
  • Ground (PE) cable
Recommended accessories

  • Current cables 2 x 10 m 10 mm2    (32.8 ft, 7 AWG) and Sense cables    2 x 10 m (32.8 ft) with TTA clamps
  • Sense cables 2 x 2 x 10 m
       (32.8 ft) with TTA clamps
  • Current connection cable 2 x 5 m    10 mm2 (16.4 ft, 7 AWG) with TTA    clamps
  • Cable plastic case – medium size
  • Current clamp 30/300 A supplied    from the instrument with extension    5 m (16.4 ft)
  • Transport case
Optional accessories

  • Test shunt 150 A / 150 mV
  • Temperature sensors 4 x 50 mm    (1.97 in) + 10 m (32.8 ft) cable set
  • Thermal printer 80 mm (3.15 in)    (built-in)
  • ICP Accelerometer with 10 m    connecting cable and mounting    tools
  • Current cables 2 x 15 m 10 mm2    (49.2 ft, 7 AWG) and Sense cables    2 x 15 m (49.2 ft) with TTA clamps
  • Current cables 2 x 20 m 16 mm2    (65.6 ft, 5 AWG) and Sense cables    2 x 20 m (65.6 ft) with TTA clamps
  • Bluetooth communication module


The DV-Win software enables control and observation of the test process, as well as saving and analyzing the results on a PC. It provides a test report, arranged in a selectable form as an Excel spreadsheet, PDF, Word, or ASCII format. The software provides an OLTC (tap changer) condition assessment through analysis of the graphs representing dynamic resistance values during the tap changer transitions.

Additionally, the DV-Win measures and calculates the OLTC transition time, the ripple and the winding resistance for each tap changing operation. The software also enables the recording of tap changer motor current, which is used for detecting motor and mechanical problems.
The software also enables obtaining the Hot Spot temperature, as a result of the Heat Run test, along with temperature and resistance graphs representing the cooling process.
The standard interface is USB. RS232 is optional.



Application Notes

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