Transformer turn ratio test (also known as turns ratio test or TTR test) is a very important test item to ensure the healthy operation of the transformer. The transformer ratio test makes the transformer have the correct ratio of primary to secondary turns. Precise transformer ratio testing can help analyze the performance of the tap changer, determine if the tap changer is in the correct position, determine a winding short circuit or open circuit winding after a transformer failure, incorrect winding connections and other internal transformer faults, and whether the transformer is faulty can run in parallel.
Transformer ratio test currently uses automatic ratio change test equipment to test, compared to the traditional current method and voltage method test method, change ratio tester has a test speed, accurate test results, easy operation, etc. , Now list the five of the most popular transformer turns ratio testers in the world:
1. TTRU3 (Brand: Megger United States)
Product Page: https://www.megger.com/en/blog/ttru3-api-integrated-testing
This instrument is a variable ratio tester manufactured by Megger Company. It is characterized by accurate measurement, phase difference and excitation current measurement, remote control test function, and TTR measurement of CT and PT. This instrument is equipped with a large color The screen has a beautiful appearance, but the high price of the TTRU3 will allow many users to consider other more economical testers.
Key Features: True three-phase step-up testing, 250 V excitation, high accuracy ±0.05%, 10-second test speed, 7" touchscreen, automatic vector recognition
Main Advantages:High efficiency and precision, supports complex transformer types, intuitive interface, lightweight and portable, strong data management capability
Limitations: Higher cost(around$13,000), requires dedicated test leads, training needed for advanced functions, depends on external power supply and USB interface
2. ATRT-01 S3 (Brand: Vanguard United States)
Product Page: https://www.dv-power.com/product/transformer-turns-ratio-testers/transformer-turns-ratio-tester/
This instrument is vanguard's fourth-generation instrument, which can be independently tested or controlled by a computer. It can calculate the percentage error of the ratio, can display the polarity and phase angle of the winding, and can also display the excitation current, but the LCD display seems to be some outdated, the process is a bit tedious when used with a keyboard.
Key Features ：
Microprocessor-based, fully automatic single-phase transformer turns-ratio tester; line-powered (ATRT-01 S3) or battery-powered (ATRT-01B S3); compliant with IEEE C57.12.90; two selectable test voltages (4 Vac and 40 Vac); measures ratio, excitation current, winding polarity, phase angle, and error percentage; internal (128 records) and USB (up to 999 records) storage; RS-232C computer interface; backlit LCD; compact and portable.
Main Advantages：
Cost-effective; integrated multi-parameter testing; flexible operation modes (standalone or computer-controlled; AC or battery); strong data management with software support; user-friendly interface suitable for varied lighting conditions.
Limitations：
Supports only single-phase testing; test voltages limited to 4 V and 40 V may restrict use on high-capacity transformers; uses legacy RS-232C interface; included analysis software geared toward older Windows platforms; internal storage capacity is limited, requiring frequent data offloading.
3. JYT (Brand: Kingrun China)
Product Page: https://www.kritester.com/product/JYT-Portable-transformer-turn-ratio-tester.html
The JYT Handheld Transformer turns ratio tester, developed by Kingrun in 2018, weighs only 1.8 kg. In addition to turns ratio testing, it offers features such as three-phase grouping testing, polarity testing, and excitation current testing. It is equipped with a multifunctional color touch LCD screen, making it easy and intuitive to operate. A single charge can test hundreds of transformers. This tester is economically priced and highly popular among transformer manufacturers.
Key Features ：
The JYT handheld transformer turns ratio tester features a multi-core ARM CPU for true three-phase simultaneous testing with ultra-fast 1.2-second results. It is lightweight (1.6 kg), powered by a long-lasting lithium battery (800+ tests), and equipped with a 5.6-inch touchscreen, USB/Bluetooth data export, and safety protections. Highly portable and compatible with multiple transformer types, it offers efficient, accurate, and safe field testing.
Key Advantages
- True three-phase testing, stable and powerful ARM CPU, fast execution, and high test efficiency
- Extremely portable with long battery life, suitable for complex field operations
- Compatible with 90% of transformer types on the market
- Convenient data processing via USB and Bluetooth
Limitations:
- Accuracy is moderate (±0.1%), while higher-end models (approximately ±0.05%) still fall within the high-accuracy range.
- Limited internal storage (only 100 test records) requires frequent data downloads.
- International brands may be less well-known than leading manufacturers, but offer significant price advantages.
4. TRT03A (Brand: DV power Sweden)
Product Page: https://www.dv-power.com/product/transformer-turns-ratio-testers/transformer-turns-ratio-tester/
This instrument has a single-phase, three-phase test function, test accuracy, phase angle test function, USB interface, you can use their own development of DV-Win software for data comparison analysis.In addition, this model can measure transformer excitation current and phase shift, and perform automatic vector group detection and magnetic balance for three-phase transformers and three-phase autotransformers. In addition, they have built-in three-phase power supply. Therefore, TRT standard instruments can test transformers with special configurations, such as phase shifters, rectifiers, arc furnaces, traction transformers, etc.
Key Features ：
The TRT03A is a fully automatic three-phase and single-phase transformer turns ratio tester, supporting power, distribution, and instrument transformers. It offers test voltages of 8 V, 40 V, and 100 V, with a wide ratio range (0.8–50,000) and ±0.05% accuracy. Key features include excitation current, phase angle, and auto vector group detection, plus OLTC control. It stores 10,000 results, supports USB/RS-232, optional printing, and DV-Win reporting. Its high precision enables early fault detection, automation accelerates testing, and strong EMI/RFI protection ensures reliable field performance.
Limitations ： Relatively heavy (~8 kg), limiting mobility in challenging locations
- Uses basic character LCD rather than advanced color display for interface
- Maximum voltage output of 100 V may not suffice for large/high-impedance transformers
- Requires mains power; absence of battery operation limits use in power-scarce environments
5. VTRM (Brand: VEER India)
This instrument is the VEER company's automatic ratio tester with over-current protection function, can store 200 sets of test data, the appearance of lightweight and beautiful, precision and measurement range and the above four instruments are not a small gap, but the low price It will be very attractive to customers.
Key Features ：The VTRM handheld transformer turns ratio tester automatically measures turns ratio, excitation current, voltage, polarity, and deviation with an accuracy of up to ±0.1%. It supports common transformer connections, allows for quick three-phase testing, and incorporates safety features. It stores 200 results and features a USB/RS-232 interface, ensuring efficient field operation and reliable data processing.
Limitations ：Limited internal storage requires frequent data export or updates.
- Heavier weight and less ergonomic design compared to ultra-lightweight handheld devices.
- Basic LCD interface lacks modern touch or color UI capabilities.
- Test voltage options may be insufficient for testing high-impedance or large-capacity transformers.
- VTRM is still undergoing market testing and is more widely used in the Indian and Southeast Asian markets., but the price is very attractive.
What is the Difference between "Ratio" and "Turn Ratio" in a Transformer Testing?
How to Choose the Right Turns Ratio of CT/PT?
Why is it so Important to Test Transformer Turn Ratio?
What are the Reasons for Abnormal Voltage Output of Power Transformers?
Kingrun Transformer Instrument Co.,Ltd.
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