Issues related to DC withstand voltage testing and AC withstand voltage testing
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In the motor industry, the power-frequency AC voltage withstanding test has always been considered the most stringent test for evaluating motor performance. However, this test also causes some damage to the insulation system of the equipment, and there is a cumulative effect; it cannot be performed multiple times. The DC voltage withstanding test causes less damage to the insulation system. It is unclear whether AC or DC voltage withstanding tests should be conducted during regular routine inspections in power plants Also, those who are familiar with it, let’s discuss just how significant the DC withstand voltage test is for today’s mica-type insulation systems :)
From the internet: 1. The Withstanding Voltage Test, also known as a Hipot Test or Dielectric Strength Test, is probably the most well-known test and the one that is used most frequently in the safety testing processes for products. 2. The voltage withstanding test is a non-destructive test used to determine whether a product’s insulation capacity is satisfactory under transient high voltages that occur frequently. It applies high voltage to the device under test for a certain period of time to ensure that its insulation performance is strong enough. 3. Test voltage: Most safety standards allow the use of either AC or DC voltage in voltage withstanding tests. When an AC test voltage is used, the insulator under test is subjected to the greatest stress at the voltage peak, whether it is a positive or negative peak. Therefore, if it is decided to use a DC voltage for testing, it is necessary to ensure that the DC test voltage is times the AC test voltage, so that the DC voltage can be equivalent to the peak value of the AC voltage. For example, for an AC voltage of 1500V, to generate the same level of electrical stress with a DC voltage, it is necessary to use 1500×1.414, which equals 2121V for the DC voltage. 4. One of the advantages of using a DC test voltage is that, in DC mode, the current flowing through the current measurement device of the voltage withstanding test instrument is the actual current flowing through the sample. Another advantage of using DC testing is that the voltage can be applied gradually. By monitoring the current flowing through the sample as the voltage increases, the operator can detect it before breakdown occurs. It should be noted that when using a DC voltage withstanding test instrument, 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 or the product’s characteristics, it is beneficial to discharge it before operating it. 5. The drawback of the DC withstand voltage test is that it can apply the test voltage in only one direction; it cannot exert electrical stress on both polarities as is the case with AC testing, and most electronic products operate under AC power supply. Furthermore, since it is difficult to generate a DC test voltage, DC testing is more costly than AC testing. 6. The advantage of the AC withstand voltage test is that it can detect all voltage polarities, which is closer to the actual practical conditions. Furthermore, since alternating voltage does not charge the capacitor, in most cases it is not necessary to gradually increase the voltage; by directly outputting the appropriate voltage, a stable current value can be obtained. Furthermore, after the communication test is completed, there is no need to discharge the sample.