Tap Changer Analyzer & Winding Ohmmeter RMO25TD



The Tap Changer Analyzer & Winding Ohmmeter RMO25TD instrument is designed for winding resistance measurement of inductive objects, and for a tap changer analysis. The RMO25TD instrument is based on the state of the art technology, using the most advanced switch mode technology available today. The RMO25TD instrument is accurate (0,1%), powerful (up to 25 A) and lightweight (9,5 kg / 20.9 lbs). It generates a true DC ripple free current with automatically regulated measurement and discharging circuit.

The RMO25TD 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.


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 10 m (32.8 ft) with TTA clamps
  • Current connection cable 1 x 5 m 10 mm2 (16.4 ft, 7 AWG) with TTA clamps
  • Cable bag
  • Current clamp 30/300 A supplied from the instrument with extension
    5 m (16.4 ft)
Optional accessories

  • Test shunt 150 A / 150 mV
  • Thermal printer 80 mm (3.15 in) (built-in)
  • Transport case
  • 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
  • PT100 temperature indicator


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. It also enables the recording of tap changer motor current, which is used for detecting motor and mechanical problems.
The software can also perform the calculations necessary for the “Heat Run” test.

The standard interface is USB. RS232 is optional.



Application Notes

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