Select Page

Why do you need to test the turns ratio of power transformers?


The Transformer Transformation Ratio Tester is based on a single-chip microcomputer as the core for measurement calculation and automatic control, with a full English menu operation interface, a new generation of intelligence with the advantages of intuitive display, good stability, high precision, wide measurement range and no need for three-phase power supply on site. Variation ratio test equipment.


1. The sampling digital three-phase inverter test power supply has no harmonic content, and the voltage is easy to adjust, start and stop to eliminate the power influence of AC220V or sampling generator power supply.

2. Three-phase test power supply, improve test speed, and can identify transformer wiring group 0-11

3. It is suitable for a wide variety of transformers and has the function of testing Z-shaped connection transformers.

4. After the rated parameters are input once, it can automatically measure the transformer ratio, error value and automatically identify the tap position of the tap changer. For the tap changer with asymmetrical tap change, it can also accurately measure the exact position of the transformer tap changer. , can measure up to 197 tap-point tap-changers.

5. The protection function is perfect, with high and low voltage reverse connection protection, transformer turn-to-turn short circuit protection, output short circuit protection, increasing the stability of the instrument.

6. It adopts a seven-inch 65K color touch-screen LCD, which imitates the display mode of a mobile phone, and the operation is simple and fast.

7. The instrument has a non-power-off clock and data storage, which is convenient for viewing historical data.

8. The instrument not only has printout, U disk interface, but also can be equipped with RS232 interface, which is convenient for paperless office.

9. It adopts cold and temperature resistant, sealed and waterproof, drop-proof and shock-proof multifunctional engineering plastic box, which is convenient for field tests.


1. For transformers with multiple tap points, equal tap stages, tap types, and input of rated high and low voltage values ​​are to enable the test results to automatically calculate the error value, as well as the tap position where the tap changer is located. , once the rated data is input, when testing each tap 

point, the error value of the point and which tap point it is (that is, the number of tap positions) can be automatically calculated, and there is no need to change the data.

2. The equal tap level, also called the tap distance, the transformer with the voltage combination of 110±8×1.25%/10.0, 1.25% is the equal tap level.

3. Tap type, transformer with voltage combination of 110±8×1.25%/10.0, equal tap level is 8+1, that is, 9, that is, input rated contacts can be used, so for transformers whose rated tap position is not at the middle point, for The measurement of the tap position is also error-free.

4. Transform ratio, when applying three-phase power to the test product, the measured voltage ratio between high voltage and low voltage, and the turns ratio is the ratio between the number of turns of the high voltage and low voltage windings. For transformers where the high voltage is star-connected (with or without a neutral point) and the low voltage is delta-connected, the transformation ratio is √3 times the turns ratio value. For transformers where the low voltage is star-connected (with or without neutral) and the high voltage is delta-connected, the turns ratio value is √3 times the turns ratio value.

5. For transformers with 19 gears of the on-load tap changer, if the taps 9, 10 and 11 are the same value, 9 should be input when the instrument inputs the tap type.

6. For transformers with the tap changer on the low voltage side, the displayed tap position and the actual tap position are inverted.

7. For transformers with low voltage levels, when the effective digits of the input voltage value are not enough, the high and low voltage voltages can be multiplied by constants such as 10 or 100 at the same time and then input.

8. When testing a single-phase transformer, just select the measurement method as “single-phase measurement”.

9. Three-phase measurement: measure the ratio and error according to the input connection method and group number.
Three-phase group: group number, ratio and error can be measured.

Test purposes

1. Check whether the transformation ratio is consistent with the value on the nameplate to ensure that the required voltage transformation is achieved.

2. Check whether the indication position of the voltage tap changer is correct.

3. Check the turns ratio of each coil to judge whether there is an inter-turn short circuit in the transformer.

4. Measure the unbalance of the transformation ratio of the three-phase transformer itself.

5. Provide the accuracy of the transformation ratio to judge whether the transformers can run in parallel.