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Wednesday, July 10, 2013

Fast Transient Test (EFT)

If you have worked on electronics company, you would had  familiar with Fast Transient Test or EFT. EFT is term of power tests such as electrostatic discharge (ESD), lightening surge, or AC transient. Fast transient test using a non continuous voltage, we can call it as surge but in high frequency. These voltage is injected on the power line to give a disturbance. 

Our country power line using frequency standard about 50 Hz, and for EFT voltage is about 5kHz, so call is high frequency. You might be get confuse, but it's ok, lest learn it deeper. 
Picture 1, EFT illustration
Picture 1 is illustration how fast transient voltage work. This voltage was injected on the power line with specified frequency, voltage and timer.  Picture bellow us example of EFT Standard:
Picture 2, EFT Spec.
Voltage magnitude which used about 4 kV (plus and minus), we check both of level voltage. The frequency is about 5 kHz, burst period about 300 ms, with 75 pulse. All of this applied into power line for 5 minutes. The device under test (DUT) did not allowed freeze on video or stopped suddenly.

when your device is NG, its mean there is a problem with your power conversion source, in this case we call it as Switch mode power supply (SMPS). and the fist thing that you should do is check the line filter on the high voltage, ensure the linkage inductance each filter both ground and line. Measure the noise level on power line and ground noise, when it big enough then add a capacitance of Y-capacitor that junction between low voltage and high voltage. 

Picture 3, Line filter of SMPS
measure the linkage induction, when it to big, you should change with another line filter better. now, think your device would have better performance, and if it's does not work, check on the ground side, and try to add capacitance of Y capacitor. Good luck guys.


Tobecontinued...





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