Technical measurement methods for light high voltage test transformers

　　The measurement of AC withstand voltage test voltage of light test transformer belongs to the measurement of stable high voltage. The commonly used methods are as follows:

　　a. Test transformer low voltage side measurement

　　This method measures the voltage on the low voltage side and then converts it to the voltage on the high voltage side through a transformation ratio. This method is simple and intuitive, but has low accuracy, especially when the load capacity is large, the error is greater.

　　b.Measurement with voltage transformer

　　Connect the primary side of the voltage transformer to the two ends of the test product, measure the voltage on the secondary side, and calculate the voltage on the high-voltage side based on the measured voltage and the transformation ratio of the voltage transformer .

　　c. Measure with a high voltage electrostatic voltmeter

　　This method can directly measure the effective value of the power frequency voltage, but it is not suitable for field use.

　　d. Measure the gap between copper balls

　　The air gap formed by spherical electrodes of a certain diameter has a certain discharge voltage at a certain gap distance if the external conditions are inconvenient; the discharge voltage changes with the change of distance. Using this characteristic, the ball gap can be used to measure the voltage, and the ball gap measures the peak value of the AC voltage.

　　When conducting power frequency AC withstand voltage test, the following matters should be noted:

　　(1) The AC withstand voltage test should be carried out under the conditions that the ambient temperature is not less than 5°C and the relative humidity is not higher than 80%.

　　(2) The test product and test equipment should be properly grounded, and the high-voltage lead should have sufficient mechanical strength.

　　(3) The voltage must be increased from zero and the circuit breaker cannot be closed by impact. The voltage increase speed can be any within 40% of the test voltage, and the voltage must be increased evenly thereafter, at a speed of about 3% of the test voltage per second.

　　(4) To prevent the test voltage waveform from being distorted, capacitive test products should be free from voltage resonance.

　　(5) The insulation resistance of the test product should be measured before and after the voltage withstand test.

　　(6) The test should be carried out only after the insulation resistance and absorption ratio, DC leakage and dielectric loss tangent tests are passed.

　　(7) The duration of the AC withstand voltage test after the standard voltage of the test piece is applied is generally 1 minute.

　　(8) After the test is completed and the power supply is disconnected, the test product must be immediately checked for any heat generation.