TWA Series

The TWA series of tap changer & winding analyzers / three-phase winding resistance meters is designed for six-winding resistance measurement of power and distribution transformers, as well as other inductive test objects. In addition, they provide powerful tap changer analysis options by using proprietary, non-intrusive DVtest features.


Six-winding, three-phase winding resistance meter measure with TWA series instruments requires only one single-step cable setup. Each power transformer configuration has a special, dedicated measurement algorithm. The winding resistance test results are stabilized quickly, and testing can be performed much faster compared with other winding ohmmeters. The test current can be automatically conducted through the HV and LV winding simultaneously.

The TWA40D model is a true three-phase winding resistance meter capable of simultaneously measuring resistances of three phases of YN configuration in the special Quick YN test mode. All TWA models are capable of both single-phase and three-phase automated demagnetization of power transformers. The DV-Win PC software, which provides full control of all TWA functions from a PC and additional test and analysis modes and features is included with the TWA series instruments.

The test leads for TWA series 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.

  • Dynamic resistance measurement (DVtest) of on-load tap changers, which can be performed simultaneously on all three phases, or on a single phase
  • On-load tap changer motor current measurement
  • Six-winding measurement of transformer winding resistances with a one-time cable connection
  • Fully automated test mode, with automatic detection of result stabilization
  • Quick YN test mode, which enables measuring the resistances of three transformer windings in the YN configuration simultaneously.