Comparison of advantages and disadvantages between AC withstand voltage test and DC withstand voltage test

Advantages and disadvantages of AC test and DC test

Please confirm with the safety regulation unit designated by the product under test what voltage the product should use. Some products can accept both DC and AC test options, but there are still many products that can only accept one of DC or AC test. If the safety regulations allow simultaneous DC or AC testing, the manufacturer can decide which test is appropriate for the product. To achieve this goal, users must understand the advantages and disadvantages of DC and AC tests.

Characteristics of AC withstand voltage (ACW) test

Most of the objects to be tested for withstand voltage test will contain some discrete electrical capacity. These discrete capacitors may not be fully charged during AC test, and there will be a continuous current flowing through these discrete capacitors.

Advantages of AC withstand voltage (ACW) test

1. Generally speaking, the AC test is easier to be accepted by the safety regulation unit than the DC test. The main reason is that most of the products use AC power, and AC test can test the positive and negative polarity of the products at the same time, which is completely consistent with the environment in which the products are used and conforms to the actual use conditions.

2. Because the discrete capacitors cannot be fully charged during the AC test, but there will be no instantaneous impulse current, so it is not necessary to let the test voltage rise slowly, and the full voltage can be added at the beginning of the test, unless this product is sensitive to the impulse voltage.

3. Because the AC test cannot fill those discrete capacitors, it is not necessary to discharge the test object after the test, which is another advantage.

Disadvantages of AC test

1. The main disadvantage is that if the discrete electrical capacity of the object to be measured is large or the object to be measured is a capacitive load, the current generated will be far greater than the actual leakage current, so the actual leakage current cannot be known. 2. Another disadvantage is that the current required by the discrete capacitance of the object to be measured must be supplied, and the output current required by the instrument will be much larger than that of the DC test. This will increase the risk of operators.

Characteristics of DC test

During the DC withstand voltage test, the discrete capacitance on the object to be tested will be filled, and the capacitive current generated during the DC withstand voltage test will drop to zero after the discrete capacitance is filled.

Advantages of DC test

1. Once the discrete capacitance on the object to be measured is filled, only the actual leakage current of the object to be measured will remain. The DC withstand voltage test can clearly show the actual leakage current of the object to be tested.

2. Another advantage is that the charging current of the object to be tested needs to be supplied in a short time, and the current required to be supplied in other time is very small, so the current capacity of the instrument is far lower than the current capacity required for AC withstand voltage test.

Disadvantages of DC test

1. Unless there is no capacitance on the object to be measured, the test voltage must start from "zero" and rise slowly to avoid excessive charging current. The larger the capacitance, the longer the slow rise time required, and the lower the voltage that can be increased at one time. When the charging current is too large, it will cause the tester to misjudge and make the test result incorrect. 2. Because the DC withstand voltage test will charge the object to be tested. So after the test, we must first treat the measured object discharge before doing the next step.

3. Unlike the AC test, the DC withstand voltage test can only be conducted with single polarity. If the product is to be used under AC voltage, this disadvantage must be considered. This is also the reason why most safety regulation units recommend the use of AC voltage withstand test.

4. During the AC withstand voltage test, the peak value of the voltage is 1.4 times of the displayed value of the meter. This point can not be displayed by ordinary ammeters, and can not be achieved by DC withstand voltage test. Therefore, most safety regulation units require that if DC withstand voltage test is used, the test voltage must be increased to the same value.