The high-voltage test transformer is the basic test equipment used for AC withstand voltage test of power plants, power supply bureaus and scientific research institutions. It has passed the standards of the National Quality Supervision Bureau and is used for various electrical products, electrical components, insulation materials. Wait for the insulation strength test under the specified voltage to assess the insulation level of the product, find the insulation defect of the tested product, and measure the ability of overvoltage. It is especially suitable for power systems, industrial and mining enterprises, scientific research departments, etc. to conduct insulation strength tests under power frequency or DC high voltage on various high voltage electrical equipment, electrical components, and insulating materials. It is an indispensable important equipment for bi in high-voltage test.

working principle

AC and DC test transformer: input the power frequency power into the operation box (or operation table), and input the voltage to the primary winding of the test transformer through the auto-voltage regulator. According to the principle of electromagnetic induction, power frequency high voltage can be obtained in the secondary (high voltage) winding. After the power frequency high voltage is rectified and filtered by the high voltage silicon stack, the DC high voltage can be obtained, and its amplitude is 1.4 times the effective value of the power frequency high voltage. It's just that the short-circuit bar should be drawn out when using DC, and the short-circuit bar should be inserted when using AC.

Test transformer with tap

In order to satisfy the contradiction between a transformer with a higher voltage and a lower voltage and a lower current and a higher current, the high-voltage winding is divided into two windings, one is the winding with the larger current, the other is the winding with the smaller current, and then The two windings are connected in series and led out separately.

Instructions

In the power frequency withstand voltage test, the current-limiting resistor R1 should be selected according to the rated capacity of the test transformer. For example, when the rated output current of the high-voltage side is 100-300MA, it can be 0.5-1Ω/V (test voltage); when the rated output current of the high-voltage side is more than 1A, it can be 1Ω/V (test voltage). Hydroelectric cathodes are commonly used as current limiting resistors. The length of the tube can be considered as 150KV/m, and the tube and thickness should have sufficient heat capacity (preparation method of water resistance liquid: use distilled water to add appropriate amount of copper sulfate to make various cathode values).

Ball gap and protective resistance: When the voltage exceeds the set value of the ball gap (generally 110%-120% of the test voltage), the ball gap discharges to protect the tested product. The ball gap protection resistance can be selected according to 1Ω/V (test voltage).

In the power frequency withstand voltage test, the measured voltage (instrument voltage) on the low-voltage side is not very accurate. The voltage on the product is lower or higher than the voltage reflected on the low-voltage side measuring voltmeter. In the power frequency withstand voltage test, the voltage on the tested product is higher than the output voltage of the test transformer, which is the so-called capacity rise phenomenon. During induction withstand voltage test. The leakage reactance of the test transformer must have a voltage drop. In order to accurately measure the voltage applied to the tested product, an RCF resistor-capacitor voltage divider is often connected to the high-voltage side to measure the voltage.