The Tap Changer & Winding Analyzer TWA40D is designed for six-winding resistance measurement and simultaneous three-phase on-load tap changer analysis of both the primary and the secondary transformer windings. This is performed with a one single-step cable setup, with test currents of up to 40 A. Each transformer configuration has a special measurement algorithm which is optimized for the fast stabilization of test results.

Additional testing mode, Quick YN, is enabled by the DV-Win software. In this mode, it is possible to measure the resistances of three transformer windings in the YN configuration simultaneously. It is also possible to test the resistances of all tap changer positions of all three phases in a single pass through the tap changer positions.