Winding Ohmmeter RMO50TW



The Winding Ohmmeter RMO50TW is a portable and lightweight instrument (8,5 kg / 18.7 lbs) designed for the winding resistance measurement of inductive test objects and for on-load tap changer verification. The RMO50TW instrument generates a true DC ripple-free current with automatically regulated measurement and discharging circuit. The injection of current and discharge of energy from the test object are both automatically regulated. The three independent channels enable testing of three windings in series. This instrument enables measurements of a winding resistance in every tap position of an on-load tap changer without discharging between the tests. Problems with switching of the OLTC, such as interruption, can be detected with these measurements.


Included accessories

  • DV-Win software
  • USB cable
  • 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
  • Transport case
Optional accessories

  • Test shunt 150 A / 150 mV
  • Thermal printer 80 mm (3.15 in) (built-in)
  • Cable bag
  • Device bag
  • 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.
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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