Test voltage, most of the safety standards allow the use of AC or DC voltage in withstand voltage test. If AC test voltage is used, when the voltage peak is reached, whether it is positive or negative, the insulator to be tested will bear the maximum pressure.<br>Therefore, if we decide to use DC voltage test, we must ensure that the DC test voltage is n times of the AC test voltage, so that the DC voltage can be equivalent to the AC voltage peak. One of the advantages of using DC test voltage is that in DC mode, the current flowing through the alarm current measuring device of withstand voltage tester is the real current flowing through the sample. Another advantage of using DC test is that the voltage can be applied gradually. By monitoring the current flowing through the sample as the voltage increases, the operator can detect the breakdown before it occurs. It should be noted that when using the DC withstand voltage tester, the sample must be discharged after the test due to the charging of the capacitor in the circuit. In fact, no matter what the test voltage is or the characteristics of the product, it is beneficial to discharge the product before operation. The disadvantage of DC withstand voltage test is that it can only apply the test voltage in one direction, and can not apply the electric stress on two polarity as AC test, and most electronic products work under AC power supply. In addition, because DC test voltage is difficult to generate, the cost of DC test is higher than that of AC test. The high voltage of DC withstand voltage test plays a special role in finding some local defects of insulation, which can be carried out simultaneously with leakage current test. Compared with AC withstand voltage test, DC withstand voltage test has the advantages of light test equipment, less insulation damage and easy to find local defects. Compared with AC voltage withstand test, the main disadvantage of DC voltage withstand test is that DC voltage withstand test is closer to the actual insulation test than AC voltage withstand test because of the different voltage distribution in the insulation under AC and DC voltage.<br>
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