Three-phase winding resistance analyzer with a touch screen and a fully automatic test
The TWA Advanced Series measures the resistance of all six windings - primary and secondary - of three-phase transformers and autotransformers and analyses the on-load tap changer with simultaneous DVtest, motor current and vibration, under IEC 60076-1.
Advantages
Fully automatic test across several positions
The tap-changer control unit, built into the instrument, steps through the selected positions without operator intervention and automatically detects when each reading has stabilised, from the touch screen itself.
Simultaneous DVtest, with motor current and vibration
The TWA500 and TWA400 models record DVtest with a 0.1 ms resolution, on one phase or all three at once, together with the tap-changer motor current and, with an optional accelerometer, its vibration.
Quick YN mode for three simultaneous phases
On a YN-connected winding, the instrument measures all three phases at once and checks the synchronisation between them, with a combined current of up to 40 A DC.
Touch screen, 32 GB of memory and dual interface
A 10.1 inch (TWA500) or 7 inch (TWA400) touch screen stores test templates and results in 32 GB of memory, with USB or Ethernet output.
Applications
- Commissioning and maintenance of power and distribution transformers and autotransformers with an on-load tap changer.
- Tap-changer condition assessment combining simultaneous DVtest, motor current and mechanism vibration.
- Synchronisation check between the phases of a three-phase tap changer.
- Fully automatic test mode across several tap-changer positions, without manual intervention.
About the product
The Advanced range comprises two models, TWA500 and TWA400, which share almost every feature - resistance range, test current, DVtest resolution and the motor and vibration channels - and differ only in touch screen size, 10.1 inches versus 7, and in the built-in thermal printer, exclusive to TWA400.
Both models share their H and X leads with TRT, so a single connection chains several tests together without rewiring the transformer. Accessories available: H and X cable sets with TTA clamps, a 30/300 A current clamp, an ICP accelerometer, a temperature sensor, a transport case and, for TWA400, a 58 mm thermal printer.
Technical specifications
| Models | TWA500 and TWA400 |
| Measurement | Three-phase, six windings, with a single cable connection |
| Resistance range / accuracy | 0.1 μΩ - 10 kΩ; from ±0.1% of reading |
| Test current | 5 mA - 25 A DC; up to 40 A DC during synchronisation check |
| DVtest resolution | 0.1 ms, on one phase or all three at once |
| Display / internal memory | 10.1 in (TWA500) or 7 in (TWA400) touch screen; 32 GB |
| Dimensions and weight | 505 × 257 × 409 mm, 13.5 kg (TWA500); 543 × 218 × 427 mm, 15.0 kg (TWA400) |
Frequently asked questions
What is the difference between TWA500 and TWA400?
Mainly the touch screen size - 10.1 inches versus 7 - and the optional thermal printer, exclusive to TWA400; test current and DVtest are the same on both models.
How does it differ from the TWA Standard range?
The Advanced range adds a touch screen with test templates, a fully automatic mode, a vibration channel, 32 GB of memory and Ethernet; the Standard range uses an LCD screen and stores 500 records.
What is the tap-changer synchronisation check?
A test that measures the dynamic resistance of all three phases at once during switching, with a combined current of up to 40 A DC, to confirm that the taps change in a synchronised way.
Is a computer needed for the automatic mode?
No: the touch screen already includes the test templates and the automatic mode; the PC software is optional and is used to prepare and analyse the results in more detail.
