Withstand Voltage International Standard
Because EMI filter is installed at the input end of the protected equipment, its reliability will directly affect the safety of the protected equipment, especially the AC EMI filter. We might take the international standards as reference.
The withstand voltage standard of the major industrial countries is different, for example:
Germany VDE0565.2 Hi-pot test(AC) P, N→E 1.5kV/50Hz 1min
Switzerland SEV1055 Hi-pot test(AC) P, N→E 2Un+1.5kV/50Hz 1min
※If the maximum working voltage Un=250V(AC) then 2Un+1.5kV=2kV
America UL1283 Hi-pot test(AC) P, N→E 1kV/60Hz 1min
Germany VDE0565.1 Hi-pot test(DC) P→N 4.3UnkV 1min
※If the maximum working voltage Un=250V(DC) , then 4.3Un=4.30.25=1.075kV
Switzerland SEV1055 Hi-pot test(DC) P→N 4.3UnkV 1min
America UL1283 Hi-pot test(DC) P→N 1.414kV 1min
Then why the withstand voltage stipulated in the safety regulations is much higher than the rated voltage? The main reason is as the following:
Normally the output voltage of power grid is 220VAC 50HZ, considering the network fluctuation, international tend to adopt 250VAC 50HZ as rated voltage. But the power grid produces surge voltage in the process of load switching. According to statistics, more than 90% of the surge voltage is about 2 times of the rated voltage, if we change the effective value of surge voltage to peak value:
This is the scientific basis for international withstand voltage safety regulation formulation.
For EMI filters, it is common mode and differential mode capacitors which must meet the withstand voltage requirement. For common mode capacitors, it is 1.5kV~2kV for 1min, and for differential mode capacitors, it is 1.075kV～1.414kV for 1min.
How to Test Withstand Voltage
Withstand voltage means the test voltage of line to line and line to ground.
Important notes :
(1) Test method: The voltage starts from zero and slowly rises to test voltage with a speed lower than 150V/S and lasts for 1 minute, the following phenomena shouldn’t occur, such as filter sparking, breakthrough, damage, etc.
(2) We implement 100% voltage test for all the filters sent out. Customers should not repeat to apply test voltage to filters for many times.
(3) Once the test is done, please make sure to drop the test voltage to zero and discharge the voltage of the internal components of filter through a suitable resistor.