The TWR-H is a battery-powered handheld tester that gathers three transformer tests in one device: turns ratio with excitation current and phase shift, winding resistance and core demagnetization. All with the same cable set and a single connection.
Advantages
Two DC current sources
One source of up to 2 A tests the high-voltage winding and another of up to 10 A the low-voltage one: each winding of a distribution transformer is measured with the right current, even simultaneously.
Ratio up to 20 000
The test voltage is chosen among 40, 10 and 1 V AC; at 1 V the ratio of current transformers is verified without saturating them, and the deviation from the nameplate is calculated automatically.
Automatic demagnetization
After the resistance test the device demagnetizes the core automatically and safely, leaving the transformer ready for service or for further diagnostic tests.
A full day on one charge
The user-replaceable Li-Ion battery lasts a complete day of testing, and the device also runs connected to the mains.
Applications
- Turns ratio of single-phase and three-phase distribution transformers.
- Ratio and polarity verification of instrument transformers.
- Winding resistance of transformers, motors and generators.
- Excitation current and phase angle.
- Demagnetization of transformers, motors and generators.
About the product
Winding resistance is measured from 1 µΩ to 3 kΩ with an accuracy of ±(0.5% of reading + 0.5% FS), and the ratio with accuracy from ±0.1%. The memory organizes 100 transformer records with up to 30 results each, and the DV-TR software receives the results over Bluetooth to analyse them and create customized reports.
Accessories: H- and X-side cables with clamps, jumper cable, mains adapter, verification shunt and a transport case with IP67 protection.
Technical specifications
| Tests | Ratio, winding resistance and demagnetization |
| Turns ratio | 0.8 – 20 000 (at 40/10 V AC); accuracy from ±0.1% |
| DC sources | Up to 2 A (HV side) and up to 10 A (LV side) |
| Winding resistance | 1 µΩ – 3 kΩ; ±(0.5% rdg + 0.5% FS) |
| Battery | 14.8 V Li-Ion, replaceable; up to 100 tests |
| Memory and communication | 100 records; Bluetooth to PC |
| Protection | IP40; IP67 in the closed case |
| Dimensions and weight | 170 × 310 × 58 mm; 1.4 kg |
Frequently asked questions
Why two current sources?
Distribution transformers have a high turns ratio and very different resistances on the HV and LV sides; with one source per side, both windings are tested with the correct current.
Does it work on current transformers?
Yes. The 1 V AC test voltage verifies the ratio and polarity of most current transformers without saturating the core.
When does the core need demagnetizing?
After any DC test, such as winding resistance: remanent magnetism distorts other tests and causes high inrush currents.
How are the results transferred to the computer?
Over Bluetooth, with the included PC software: stored records are analysed at the office and turned into customized reports.
