Three-Phase Winding Ohmmeters & Tap Changer Analyzers

The TWA series instruments are designed for six-winding resistance measurement of power and distribution transformers, as well as resistance measurement of inductive test objects. In addition, they provide powerful tap changer analysis options by using proprietary, non-intrusive DVtest features. They generate true DC ripple free current with automatically regulated measurement and discharging circuit.

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TWA Series

The TWA series instruments are designed for six-winding resistance measurement of power and distribution transformers, as well as resistance measurement of inductive test objects. In addition, they provide powerful tap changer analysis options by using proprietary, non-intrusive DVtest features. They generate true DC ripple free current with automatically regulated measurement and discharging circuit.

The transformer measurements performed with the TWA instruments require only one single-step cable setup. Each transformer configuration has a special measurement algorithm which is optimized for the fast stabilization of test results. The test current can be automatically passed through the HV and LV winding simultaneously in order to achieve shorter stabilization times.

The TWA40D model is a true three-phase instrument capable of simultaneously measuring winding resistances of three phases of YN configuration, as well as three-phase tap changer analysis. All TWA instrument models are capable of both single-phase and three-phase demagnetization. The DV-Win software, which provides full control of all TWA functions from a PC, as well as additional test and analysis modes and features, is included with the TWA instruments.

TWA25A TWA40D
Six-winding resistance measurement yes yes
DC test current 5 mA – 25 A 5 mA – 25 A; up to 25 A for winding resistance measurement and up to 40 A for the 3-phase synchronization test
Measurement accuracy ± (0,1 % rdg + 0,1 % FS) ± (0,1 % rdg + 0,1 % FS)
Simultaneous 3-phase winding resistance measurement no yes
DVtest sampling resolution 4 ms 0.1 ms
Simultaneous 3-phase DVtest no yes
Tap changer motor current measurement no yes
3-phase demagnetization yes yes
Interchangeable test leads with TRT turns ratio testers yes yes
USB flash drive feature yes yes
Built-in tap changer control unit yes yes

YES-YES, NO-NO

TWA-TRT Safety Switchbox

TWA-TRT Safety Switchbox

The TWA-TRT Safety Switchbox is an optional accessory for TWA series of Tap Changer & Winding Analyzers and TRT series of Transformer Turns Ratio Tester, which share the common test leads. It ensures the safety of the operator during the change of test leads from one instrument to the other by safely grounding the test leads during the change of instruments.

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