The withstand voltage test is a non-destructive test that is used to determine if the insulation of a product under transient high voltages is acceptable. It applies a high voltage to the equipment under test for a certain period of time to ensure that the insulation of the equipment is sufficiently strong.
Test voltage, most of the safety standards allow the use of AC or DC voltage in the voltage test. If the AC test voltage is used, when the voltage peak value is reached, the insulator under test will withstand the maximum pressure regardless of whether the positive or negative polarity peaks. Therefore, if you decide to choose to use a DC voltage test, you must ensure that the DC test voltage is twice the AC test voltage, so that the DC voltage can be equated with the AC voltage peak. For example: 1500V AC voltage, for the DC voltage to produce the same amount of electrical stress must be 1500 × 1.414 or 2121V DC voltage.
One of the benefits of using a DC test voltage is that in the DC mode, the actual current flowing through the sample flows through the Hipot's alarm current measuring device. Another advantage of using a DC test is that it can gradually apply voltage. By monitoring the current flowing through the sample as the voltage increases, the operator can detect before the breakdown occurs. It should be noted that when using a DC voltage tester, the sample must be discharged after the test is completed due to the charging of the capacitor in the circuit. In fact, regardless of the test voltage and the characteristics of its products, it is beneficial to discharge the product before operating it.
The disadvantage of the DC withstanding voltage test is that it can only apply the test voltage in one direction, and cannot exert electrical stress on the two polarities like the AC test. Most electronic products work under AC power. In addition, because the DC test voltage is harder to generate, the DC test costs more than the AC test.
The advantage of AC withstand voltage testing is that it can detect all voltage polarities, which is closer to the actual practical situation. In addition, since the AC voltage does not charge the capacitor, in most cases, it is not necessary to gradually increase the voltage, and a stable current value can be obtained by directly outputting the corresponding voltage. Also, after the AC test is completed, no sample discharge is required.
The disadvantage of AC withstand voltage testing is that if there is a large Y-capacitance in the line under test, in some cases, the AC test will be misjudged. Most safety standards allow the user not to connect the Y-capacitor before testing, or instead use a DC test. The DC voltage test does not misjudge when the voltage is raised in the Y capacitor because the capacitor will not allow any current to pass through.
AC withstand voltage test is the most effective and direct method to identify the insulation strength of electrical equipment.
In the operation of a power device, insulation is gradually degraded by the effects of electric field, temperature, and mechanical vibration, including overall deterioration and formation of defects. For example, there are local defects due to local electric field concentration or partial insulation. All kinds of preventive test methods have their own merits. They can find some defects and reflect the status of insulation. However, the test voltages of other test methods are often lower than the working voltage of the power equipment, and they are not strong enough for safe operation. . DC voltage test Although the test voltage is relatively high, some insulation weaknesses can be found, but most of the insulation of the power equipment is a combination of dielectrics. Under the effect of DC voltage, the voltage is distributed by resistance, so the AC power equipment is The weak points under AC electric fields may not be detected using dc. The AC withstand voltage test complies with the electrical conditions of the electrical equipment during operation. At the same time, the AC withstand voltage test is generally higher than the operating voltage. Therefore, after the test, the equipment has a large safety margin, so this kind of test has become a safe operation. Is an important means.
However, because the test voltage used in the AC voltage withstand test is much higher than the operating voltage, an excessively high voltage will increase the dielectric loss, heat, and discharge, and will accelerate the discovery of insulation defects. Therefore, in a sense, AC withstand voltage test is a destructive test.
Before carrying out the AC voltage withstand test, various non-destructive tests must be carried out, such as measuring the insulation resistance, absorption ratio, dielectric loss factor tgδ, and DC leakage current, etc., and comprehensively analyze the test results to determine whether the equipment is Damp or contain defects. If it is found that there is a problem, it must be processed in advance. After the defect is eliminated, the AC withstand voltage test can be conducted to avoid insulation breakdown, expansion of insulation defects, extension of inspection time, and increase of inspection workload during the AC withstand voltage test. .
Double Sided Tissue Tape,High Viscosity Double Sided Tape,Heavy Duty Double Sided Tissue Tape,Non Woven Adhesive Tape
Shanghai Huike New Material Technology Co., Ltd. , https://www.shhuike.com