Voltage withstand test is a non-destructive test used to check whether the insulation capacity of products under frequently occurring transient high voltage is qualified. It applies high voltage to the tested equipment within a certain period of time to ensure that the insulation performance of the equipment is strong enough. Test voltage, most safety standards allow the use of AC or DC voltage in withstand voltage testing. If an AC test voltage is used, when the voltage peak is reached, whether it is positive or negative, the insulation to be tested bears the maximum pressure. Therefore, if the decision is made to use DC voltage testing, it is necessary to ensure that the DC test voltage is √ 2 times the AC test voltage, so that the DC voltage can be equivalent to the peak AC voltage. For example, 1500V AC voltage, for DC voltage to generate the same amount of electrical stress, it must be 1500 × 1.414 is 2121V DC voltage.
One advantage of using DC test voltage is that in DC mode, the actual current flowing through the alarm current measurement device of the withstand voltage tester is the current flowing through the sample. Another advantage of using DC testing is that it can gradually apply voltage. By monitoring the current flowing through the sample as the voltage increases, the operator can detect it before the breakdown occurs. It should be noted that when using a DC withstand voltage tester, due to the charging of capacitors in the circuit, the sample must be discharged after the test is completed. In fact, regardless of the test voltage and product characteristics, it is beneficial to discharge the product before operating it.
The disadvantage of DC withstand voltage testing is that it can only apply the test voltage in one direction, and cannot apply electrical stress on both polarities like AC testing. Most electronic products operate on AC power sources. In addition, due to the difficulty in generating DC testing voltage, the cost of DC testing is higher than that of AC testing.
The advantage of AC withstand voltage testing is that it can detect all voltage polarities, which is closer to practical situations. In addition, since AC voltage does not charge capacitors, in most cases, stable current values can be obtained by directly outputting the corresponding voltage without gradually increasing the voltage. And after the communication test is completed, there is no need to perform sample discharge.
The disadvantage of AC withstand voltage testing is that if there is a large Y capacitor in the circuit being tested, in some cases, AC testing will misjudge. Most safety standards allow users to not connect the Y capacitor before testing or switch to using DC testing. The DC withstand voltage test will not misjudge when applying a high voltage to the Y capacitor, as the capacitor will not allow any current to pass through at this time.
AC withstand voltage test is the most effective and direct method for evaluating the insulation strength of power equipment.
During the operation of power equipment, insulation will gradually deteriorate due to long-term effects of electric field, temperature, and mechanical vibration, including overall deterioration and the formation of defects. For example, due to the concentration of local electric fields or the fragility of local insulation, there may be local defects. Various preventive testing methods have their own strengths and can detect some defects separately, reflecting the insulation condition. However, the test voltage of other testing methods is often lower than the working voltage of power equipment, which is not strong enough as a guarantee for safe operation.
Although the DC withstand voltage test has a relatively high test voltage and can detect some insulation weaknesses, due to the fact that most of the insulation of power equipment is composed of composite dielectrics, the voltage is distributed according to resistance under the action of DC voltage. Therefore, the weaknesses of AC power equipment in the AC electric field may not be detected through DC testing. The AC withstand voltage test meets the electrical conditions that power equipment can withstand during operation, and the AC withstand voltage test is generally higher than the operating voltage. Therefore, after passing the test, the equipment has a large safety margin, so this type of test has become an important means to ensure safe operation. However, due to the fact that the test voltage used in the AC withstand voltage test is much higher than the operating voltage, excessive voltage can increase the loss of insulation medium, generate heat, discharge, and accelerate the discovery of insulation defects. Therefore, in a sense, the AC withstand voltage test is a destructive test. Before conducting the AC voltage withstand test, various non-destructive tests must be carried out, such as measuring insulation resistance, absorption ratio, and dielectric loss factor tg δ、 Conduct a comprehensive analysis of various test results, such as DC leakage current, to determine whether the equipment is affected by moisture or contains defects. If any existing problems are found, they need to be dealt with in advance. After the defects are eliminated, the AC voltage withstand test can be carried out to prevent insulation breakdown, expand insulation defects, extend maintenance time, and increase maintenance workload during the AC voltage withstand test process.
The ZC-500 power frequency withstand voltage control box (referred to as the tester) adopts CNC technology and has strong anti-interference ability. Compared with the previous generation of operation boxes, it has the characteristics of small size, light weight, and beautiful appearance. Its output voltage amplitude is continuously adjustable from 0 to 250V, used for voltage regulation control of calibration, detection, and testing equipment. The operation box is simple, compact, sturdy, reliable, and easy to maintain. It is an ideal control equipment for outdoor high-voltage testing and can be widely used in industries such as power, water conservancy, chemical, railway, and laboratories.
Kvtester Electronics Technology Co.,Ltd. is a high-tech enterprise specializing in power testing, testing, research and development, production, and sales of testing equipment. It has been engaged in the electrical testing industry for many years, and its products are of high quality. We welcome customers to come and purchase.
