Tap Changer Analyzers & Winding Ohmmeters

RMO-TW series is perfect for winding resistance measurements of inductive objects. It is ideal for testing transformer windings (power transformers, distribution, autotransformers) and for on-load tap changer verification. In addition, any RMO-TW transformer ohmmeter & tap changer analyzer can also perform transformer demagnetization.The series contains 4 models, with maximal test currents from 10 A (RMO10TW) to 50 A (RMO50TW). They are fitted in a portable and lightweight metal housing.All transformer ohmmeters from RMO-TW series generate 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 automatically regulated.Three independent channels enable testing of three windings in series. Consequently, this enables measurements of winding resistance in every tap position of an on-load tap changer without discharging between the tests.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. Additionally, 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. Finally, a user can export all results in the form of a report.

Using the most advanced switch-mode technology available today, the RMO-TD series is ideal for winding resistance measurements of inductive objects. Transformer resistance meters and tap changer analyzers are perfect for testing:transformer windings (power transformers, distribution, autotransformers),all types of tap changers,generators,electrical motors,high-current busbar joints,cable splices,and welding joints.In addition, transformer demagnetization can also be done with all RMO-TD instruments.The RMO-TD series contains 3 models, with maximal test currents from 25 A (RMO25TD) to 60 A (RMO60TD).The three independent voltage sense channels enable testing of three windings in series. This enables measurements of winding resistance in every tap position of an on-load tap changer without discharging between the tests.All RMO-TD transformer resistance meters have a built-in tap changer control unit. It enables remote control of on-load tap changer (OLTC) directly from the device. In order to make the most out of this feature, DV-Win software is included which can be programmed to do everything automatically – running winding resistance tests and changing OLTC tap positions.The DV-Win software also 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. Additionally, 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.All results can be exported in the report format.

RMO-TT series is perfect for measuring winding resistance of inductive objects such as power and distribution transformers or autotransformers. Additionally, every transformer resistance meter from RMO-TT series can analyze:tap changers,generators,electrical motors,high-current busbar joints,cable splices,and welding joints.Transformer demagnetization can also be performed with all RMO-TT instruments.The series is consisted of 3 models, with maximal test current from 40 A (RMO40TT) to 100 A (RMO100TT). RMO100TT is the only portable transformer resistance meter in the market with 100 A DC output current.The three independent channels enable testing of three windings in series. Consequently, a user can measure winding resistance in every tap position of an on-load tap changer without discharging between the tests.In addition to winding resistance measurement, a user can perform a detailed on-load tap changer analysis by analyzing recorded graphs (10 kHz sampling rate) and by measuring vibrations on an external tap changer tank.All RMO-TT instruments have a built-in tap changer control unit. Because of this, it is possible to remotely control on-load tap changer (OLTC) directly from the device. Also, a user can program DV-Win software to do everything automatically – running winding resistance tests and changing OLTC tap positions.The DV-Win software also 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. Additionally, 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.All results can be exported in the report format.

When it comes to winding resistance measurement on three-phase power transformers and autotransformers, TWA Standard series offers some of the most technically advanced instruments with LCD display in the market. Both models are capable of testing six transformer windings with a one-time cable connection, as well as three-phase automatic transformer demagnetization. The stored magnetic energy is safely automatically discharged at the end of the test. The built-in tap changer control unit enables automated test mode, where the instrument operates the tap changer without operator input and records winding resistance results based on pre-selected stabilization criteria. This option makes the operator’s job significantly easier.Both models can output test currents from 5 mA to 25 A DC for the purpose of winding resistance measurement. TWA40D has a special test mode for checking the synchronization of on-load tap changers with three phases simultaneously tested in parallel, in which the total test current can rise to up to 40 A DC.TWA40D has additional advantages when it comes to non-intrusive tap changer analysis. The unique DVtest method enables checking the moving contacts of on-load tap changers during the transition, measuring the transition time, detecting open circuits, and many other types of faults. It is performed with 0.1 ms sampling rate, simultaneously with the measurement of tap changer motor current which helps with the detection of motor and mechanical issues. A special proprietary algorithm is used for testing tap changers connected through a built-in series (booster) transformer. The DVtest can be performed either on one phase or on three phases simultaneously. It can also be performed as an additional test simultaneously with the winding resistance test in all tap positions.An additional unique advantage of TWA40D is the capability of simultaneously testing the winding resistance of all three phases of a three-phase transformer (connected in a YN configuration). This can significantly shorten the total testing time – for example, it enables the operator to perform 33 measurements instead of 99 on a tap changer with 33 tap positions.The test leads for TWA three-phase transformer winding ohmmeters are interchangeable with the TRT turns ratio testers, which means that both sets of tests can be performed with a single test lead connection to the power transformer terminals.

TWA Advanced series is the latest DV Power solution for three-phase transformer winding resistance measurement and tap changer analysis. They are capable of testing six transformer windings with a single cable connection, as well as three-phase automatic transformer demagnetization. It has the option of the automated test mode, where the instrument operates the tap changer without operator input (minimizing the risk of human error) and records winding resistance results based on pre-selected stabilization criteria.The unique DVtest method of tap changer analysis enables checking the moving contacts of on-load tap changers during the transition, measuring the transition time, detecting open circuits, and many other types of faults. It is performed with 0.1 ms sampling rate, together with the measurement of tap changer motor current which detects motor and mechanical issues. A special proprietary algorithm is used for testing tap changers connected through a built-in series (booster) transformer. The DVtest can be performed either on one phase or simultaneously on three phases. It can also be performed together with the winding resistance test in all tap positions.A unique advantage of TWA Advanced instruments is the capability of simultaneously testing the winding resistance of all three phases of a three-phase transformer connected in a YN configuration. This can significantly speed up the testing– for example, it enables the operator to perform 33 measurements instead of 99 on a tap changer with 33 tap positions.TWA500 is equipped with a large 10.1” graphical touch-screen display, while TWA400 has a 7” graphical touch-screen display. Besides making the interface much more user-friendly compared to older winding ohmmeters, it also enables certain test options that were previously available only with DV-Win software. The most important among them are DVtest, tap changer motor current measurement, “Heat Run” test, test templates, and automatic test mode.