By hvhipot 
HV Hipot Electric Co., Ltd. specializes in producing series resonance (also known as AC withstand voltage testing instruments). Next, we will share with you the problems in AC testing.
1. The situation of the regulator
When the power supply is turned on, the electromagnetic switch is turned on, and the voltage regulator is turned on, the voltage regulator will make a heavy noise. This may be that the 220 V voltage regulator is wrongly connected to the 380 V power supply. If the current at this time has an abnormal reading, it may also be that the voltage regulator is not at zero, and there is a short circuit or similar short circuit on its output side. The most common situation is that the grounding rod is forgotten to remove.
2. The condition of the voltmeter
(1) The voltmeter indicates. After the power is turned on, the voltmeter immediately shows an indication, indicating that the regulator is not at zero position. If the voltmeter shows a large reading accompanied by a sound, it may immediately detect an odor.
(2) The voltmeter has no indication. After the power supply is connected, the voltage regulator is adjusted, and the voltmeter has no indication. This may be caused by the poor contact of the carbon brush of the autotransformer, or the impassability of the voltmeter circuit, if the measuring coil (or the input coil of the transformer) of the transformer is disconnected.
3. Situations that occur during the boosting process
(1) During the process of boosting or continuous testing, internal discharge of the current limiting resistor may occur, which may be due to the lack of water or insufficient water in the tube. Sometimes there may be flashover on the outer surface of the pipe, which may be caused by excessive water resistance, short pipe, or dirty surface.
(2) During the boosting process, the changes in the voltmeter and other meters should be monitored. When the voltage rises to 0.5 times the rated test voltage, the capacitance current of the tested equipment should be read; When the rated voltage is reached, start calculating the time and slowly decrease the voltage after the time is up.
(3) For the boosting speed, it can be slightly faster below 1/3 of the test voltage, and then the boosting should be uniform, about 3% of the test voltage per second, or 10-15 seconds to reach the rated test voltage.
(4) If the pointer swings or the tested equipment or experimental equipment makes abnormal noises, smoke, or sparks during the experiment, the voltage should be immediately reduced, and a ground wire should be hung on the high-voltage side to investigate the cause.
(5) If there are no obvious regulations for the tested equipment, the general withstand voltage time is 1 minute. For insulation rods and other tools, the withstand voltage time is 5 minutes. After the experiment, the relevant parts should be touched after hanging the grounding rod, and there should be no heating phenomenon.
(6) The test voltage value should be carefully determined, especially the withstand voltage test of the generator, which must be strictly supervised and not raised above the specified value.
(7) The insulation resistance and absorption ratio of the tested equipment should be measured before and after the experiment, and there should be no significant difference between the two measurement results.