AC voltage withstand test is a very important test in high-voltage equipment testing, and selecting suitable testing equipment is of utmost importance for conducting AC voltage withstand test. Currently, there are two main types of AC voltage withstand test equipment: high-voltage test transformers andvariable frequency series resonance test devices.
High voltage test transformer
High voltage test transformers are generally divided into two series: 1. High voltage side current of 1~2A. 2. High voltage side current of 0.1~0.2A. During the test, the appropriate test transformer is selected according to the requirements of voltage, current, frequency, and capacity. The calculation method is as follows:
The main disadvantage of this method is that the experimental voltage is relatively low.
In order to solve the disadvantage of low test voltage, a series test transformer can be used to increase the test voltage, but the utilization rate decreases. For example, if two test transformers are connected in series, the efficiency is 66.7%, and if three test transformers are connected in series, the efficiency is 50%. The more stages, the lower the efficiency. Generally, it is not recommended to use test transformers with three or more levels in series, and they are not suitable for transportation.
In short, the disadvantage of using a test transformer for AC withstand voltage testing is that the test voltage is relatively low. The capacity of the test transformer is limited and it is difficult to meet the AC withstand voltage test requirements of high-voltage power equipment. It is generally used in laboratories.
The use of avariable frequency series resonance test devicefor AC withstand voltage testing can compensate for some of the deficiencies of the test transformer. Meet the requirements for AC withstand voltage testing of large capacity power equipment on site.
Thevariable frequency series resonance test devicecan be achieved by adjusting inductance, capacitance, frequency, or adjusting both of them. Previously, the variable frequency series resonance test device mainly adjusted inductance. But currently, the frequency of mediation is the most common. In addition to considering the test voltage and capacity, attention should also be paid to the test pressurization time. When the frequency is less than or equal to twice the rated frequency, the test pressurization time is 60 seconds. When the frequency is greater than or equal to twice the rated frequency, the test pressurization time is calculated as follows:
In the formula: t=pressurization time, fn=rated frequency, f=test frequency.
Remember: If the test power frequency is greater than twice the rated frequency. The test pressurization time shall not be less than 15 seconds.
