The initial transformer turns ratio (TTR) testing was conducted using a simple bridge method, such as the Maxwell or Heaviside bridges, these early devices required a series of complex, separate components—standard resistors, inductors, and galvanometers—making the testing process time-consuming, labor-intensive, and prone to calculation errors (left side of the bottom picture).

The development of transformer turns ratio (TTR) testers dates back to the early 20th century, with the hand-cranked transformer ratio testers developed by James G. Biddle，operators needed to generate excitation voltage by turning a hand-cranked generator on the side while adjusting a knob until the galvanometer pointer zeroed out (zero-balance method), and then reading the turns ratio from the scale on the knob (right side of the top picture).

By the late 20th century, the advent of microprocessors led to the creation of digital TTR testers, these devices automated the excitation and balance processes, displaying readings on an LCD screen instantly and eliminating human errors. Modern devices are now fully automated, capable of testing all three phases simultaneously, measuring phase shift and excitation current, and offering wireless data logging capabilities, from the bulky, hand-cranked wooden testers to the handheld high-precision computers, TTR testers have continuously evolved to meet the demands of the increasingly complex global power grid.

The JYT-A TTR utilizes a high-precision multi-core ARM CPU (Advanced RISC Machines, USA), delivering exceptional measurement accuracy and resolution. This fully automatic three-phase testing instrument is specifically designed for determining the turns ratio of power transformers, distribution transformers, and instrument transformers. By applying voltage to the high-voltage winding, it precisely measures the no-load voltage on the transformer windings and calculates the turns ratio by displaying the ratio of these voltages.

Based on state-of-the-art technology, the JYT-A is suitable for testing single-phase and three-phase transformers, as well as CTs, PTs, CVTs, Z-type windings, and transformers with or without neutral points and taps. It fully complies with the requirements of IEC 60076-1.

The JYT-A TTR supports testing of various transformer configurations—including single-phase, delta-star, star-delta, delta-delta, star-star, and delta-zigzag—without the need to change connection cables during measurement. Tests can be performed directly, saving time and reducing the risk of connection errors. The instrument can automatically compare test results against the nameplate voltage values entered by the user, calculate the turns ratio deviation, and print the percentage error for each measurement. Even if no reference data is provided, it can still measure the transformation ratio with high precision.

The JYT-A also features multiple protection mechanisms, including high- and low-voltage reverse connection protection, transformer short-circuit protection, and inter-turns short-circuit protection. Its excellent capability to suppress electrostatic and electromagnetic interference in high-voltage environments ensures accurate and reliable test results.

FUNCTION INTRODUCTION:

1.The interface adopts intelligent touch mode, which is simple and convenient to operate.The interface adopts an intelligent touch mode, which is simple and convenient to operate.

2.High-stability sine wave power supply; the test voltage is automatically adjusted according to the load.

3.The test data is accurate when the generator is powered, even if the quality of the power supply in the field is poor.

4.The test speed is fast. The three-phase turns ratio test can be completed in one wiring, taking only 10 seconds.

5.CT, PT, CVT, and Z-connection transformers can be tested.

6.It is suitable for ratio measurement of distribution transformers distribution transformers and power transformers, current transformers (CT), voltage transformers (PT), and Z-type transformers.

7.A variety of short circuit measurement methods are available, making fault judgment more convenient.

8.No real-time clock or date display; stores up to 200 records, and data is retained even after power loss.

9.Large color LCD display, with clear and easy-to-read data. RS485 communication interface and USB storage interface.

10.The instrument has high and low voltage reverse connection protection, as well as transformer short circuit and inter-turns short circuit protection.

11.Bluetooth communication function (optional).

JYT-A Connection with Transformer:

JYT-A TTR function interface and test result interface：

JYT-A TTR Technical Specifications:

Output Line  Voltage	≤160V AC(RMS)
Ratio Range	0.9-10000
Accuracy	Ratio <2000	±0.1%
	Ratio 2000-10000	±0.3%
Min. Resolution	0.0001
Operation Power	AC100-240V,50/60Hz, or lithium battery (Option)
Operating Temperature	-20℃～40℃
Relative Humidity	≤80%RH, no condensation
Dimensions (L × W × H)	L285mm x W218mm x H158mm
Net Weight	5 kg
Data Storage	200 sets

Frequently Asked Questions about the JYT-A:

1. What types of transformers can the JYT-A tester measure?

The JYT-A tester covers a wide range of applications — from distribution and power transformers to CTs, PTs, and even Z-type transformers.

It supports single-phase, three-phase, and 8-pole neutral point testing, making it suitable for nearly all transformer configurations in substations and factories.

2. Is it easy to operate in the field?

Yes. The JYT-A is lightweight (only 5 kg) and designed for fast on-site use.

One connection completes a full three-phase test within 10 seconds.

Its intelligent touch screen, automatic phase detection, and anti-interference design make it ideal for outdoor and substation environments.

3. How accurate is the measurement?

Accuracy is ±0.1% for ratios < 2000, and resolution reaches 0.0001.

That means the instrument can detect subtle winding faults, shorted turns, or tap-changer connection errors before they cause major issues.

Each tester follows IEC 60076 and IEEE C57.12.90 standards to ensure reliable results.

4. Can I store or export test data?

Absolutely. The JYT-A includes USB and RS-485 interfaces, with optional Bluetooth connectivity.

It can store hundreds of test records and export them to PC for analysis or trend tracking.

This makes it easy to create maintenance reports and compare test results over time.

5. Is it safe to use around high-voltage transformers?

Yes. The instrument features multiple protection layers —reverse-connection protection, inter-turn short protection, and high-voltage isolation.

It’s built to withstand strong electromagnetic interference and static discharge, ensuring operator safety during field tests.

6. What about calibration, repair, or after-sales service?

Kingrun provides 24-month warranty, lifetime technical support, and calibration service upon request.

Our engineers can guide you remotely or provide on-site support if needed.

We also stock spare parts and accessories to keep your instrument running with minimal downtime.

7. What advantages does this tester have over other brands?

Faster testing (10 s for three-phase)

Higher precision (0.0001 resolution)

Supports all transformer types (Y-Δ, Δ-Y, Z-type)

Robust data management (USB + Bluetooth + RS-485)

Factory-direct pricing and quick service

These features make it a practical long-term investment compared to rental or entry-level testers.

8. Does it comply with international standards and local requirements?

Yes. The JYT-A complies with IEC 60076-1, IEEE C57.12.90, and GB/T 1094 standards.

The software supports multiple languages and voltage configurations (up to 160 V AC output), ensuring compatibility with different grid systems worldwide.

9.Why does the JYT-A look so different from other transformer testers?

Yes — unlike conventional flip-cover designs, the JYT-A adopts an open-end terminal layout that allows test leads to extend in any direction.

This effectively reduces bending stress on the cables, preventing accuracy loss and poor contact caused by twisted or strained test wires.

Meanwhile, the high-strength housing provides professional-grade protection against vibration, dust, and water.

The enclosure meets IEC 60068 (vibration resistance) and IEC 60529 IP65 (dustproof and waterproof protection) standards, ensuring reliable performance even under harsh or extreme test conditions.

Kingrun Transformer Instrument Co.,Ltd.

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