Handheld TWR-H device is DV Power single-phase instrument designed for measuring transformer winding resistance and turns ratio.
The instrument has two output DC sources for measuring transformer winding resistance. The first DC source can output up to 2 A DC and is used for injecting current to the transformer’s high voltage winding. The second DC source can output up to 10 A DC and is used for testing the transformer’s low voltage winding. This is especially useful when measuring winding resistance of distribution transformers. These transformers have large turns ratio and therefore a big difference between resistances of high voltage and low voltage windings. Upon the winding resistance test, it is also possible to demagnetize the transformer core. The demagnetization process is completely automatic and safe.
Together with the turns ratio, the instrument also measures excitation current and phase shift. This enables detecting transformer core or winding turns failures which cannot be spotted by measuring turns ratio only. The instrument can output test voltage up to 40 V AC for this test, but it can also output a very low test voltage of 1 V AC which is necessary for turns ratio verification of the majority of current transformers.
TWR-H is powered by an internal Li-Ion battery. Up to 100 tests can be performed with a fully charged battery.