One of the various tests parameters where the transformer turns ratio (TTR) is the very basic- it is affecting the functionality of the transformer as it delivers the proper voltage and, at the same time, is a useful diagnostic tool to detect winding faults or tap changer issues. Testing transformer is a necessary action in the work of repair and diagnostics of the power systems, and it’s the parameter which is the turns ratio that is under research.
So, what is the best method to measure the transformer turns ratio with extreme accuracy?
At Baoding PUSH Electric, we regularly solve such assignments and perform experiments in the field of electric power testing. One of our latest developments is the PS-BB101A Three-Phase Transformation Turn Ratio Tester. It is a portable and reliable tool for making the necessary measurements. The engineers conducting field or lab tests will need only a few minutes to get the TTR parameter, which has an accuracy of up to the 6th significant digit. Further in this paper, we will elaborate on that, and we’ll also discuss the essential characteristics of the professional-grade testers of today’s electrical engineers.
What Is Transformer Turns Ratio (TTR)?
The transformer turns ratio is the ratio of the number of windings in the primary coil to the number in the secondary coil. This directly determines the voltage transformation level (e.g., stepping voltage up or down).
For example, a 10:1 turns ratio means that the secondary voltage will be one-tenth of the primary voltage. Deviations from expected values can indicate:
- Internal short circuits
- Incorrect winding connections
- Tap changer malfunction
- Core saturation or partial insulation breakdown
Most Accurate Method: Digital Ratio Measurement with High-Precision Testers
Traditionally, engineers relied on voltage method testing, where an AC voltage is applied to one winding and the output is measured on the other. However, this method is limited by human error, external interference, and manual calculations.
Today, the most accurate and efficient method is using an automatic three-phase transformation turn ratio tester, such as Baoding PUSH Electric’s PS-BB101A. This device automates the process by applying a known test voltage and electronically calculating the ratio with high precision.
Key Advantages of the PS-BB101A:
- Tests single-phase and three-phase transformers
- Digital display with real-time ratio, phase angle, and error analysis
- Built-in self-calibration function for stable accuracy
- Measures turn ratio error and group vector
- USB and printer output for data logging
Whether you’re inspecting power distribution transformers or testing large grid-connected units, the PS-BB101A offers unmatched speed and consistency.
Supporting Equipment for Comprehensive Analysis
While the turn ratio test is essential, it’s not the only diagnostic that matters. For accurate fault location and condition assessment, it’s crucial to integrate supporting tests.
1. 20A Transformer DC Winding Resistance Tester
Before or after TTR testing, use this tester to measure resistance in windings. This helps identify:
- Winding deformation
- Connection defects
- Inter-turn shorts
Baoding PUSH Electric’s 20A model delivers fast stabilization and high accuracy, with automatic temperature correction and multi-channel resistance comparisons.
2. PS-YC115 On-Load Tap-Changer Tester
Tap changers regulate output voltage in transformers. Malfunctioning tap changers are a major source of transformer failure.
The PS-YC115 tests on-load tap-changer contact timing, waveform distortion, and dynamic resistance—ensuring each tap operates within acceptable limits. This complements turn ratio data by validating regulation under load conditions.
Why Accurate TTR Testing Matters
Inaccurate transformer turn ratios can lead to:
- Voltage imbalance
- Overloading of connected devices
- Reduced transformer life
- Hidden internal faults leading to catastrophic failure
That’s why power utilities, OEMs, and maintenance teams rely on tools like the PS-BB101A Three-Phase Transformation Turn Ratio Tester—not just to meet regulatory standards, but to ensure grid stability and asset reliability.