Electronics > Projects, Designs, and Technical Stuff
Testing 1N4007 with a megger
<< < (6/8) > >>
taydin:
Yesterday I have also tested a 1N4001. Same behavior as the 1N4007. Broke down at about 1800V, measures ok with a multimeter. So indeed, the 1N4001 is a 1N4007 in disguise.

This begs the quesion. In the old days, when they were classifying the diodes according to their voltage rating, how did they determine the breakdown voltage? I guess there's gotta be a way to detect the onset of avalance without damaging the diode.
T3sl4co1l:
Compare Vf?

Tim
jaromir:

--- Quote from: taydin on November 02, 2019, 10:15:14 am ---This begs the quesion. In the old days, when they were classifying the diodes according to their voltage rating, how did they determine the breakdown voltage? I guess there's gotta be a way to detect the onset of avalance without damaging the diode.

--- End quote ---

They are measuring Vbr even today, not just in old days. Breakdown voltage is measured at few orders of magnitude lower current than your limit, for example Vishay declares Vbr at 5uA - see https://www.vishay.com/docs/88503/1n4001.pdf
You mentioned 3mA before (I don't know how well is the current limited in your Megger, it's not designed to test semiconductors, after all) - that is quite a lot for a small diode at 1,8kV, no wonder they got damaged, especially on repeated measurements.

The Vbr parameter is measured using current source with high compliance voltage, measuring voltage on the diode.
mzzj:

--- Quote from: jaromir on November 02, 2019, 11:23:07 am ---
This begs the quesion. In the old days, when they were classifying the diodes according to their voltage rating, how did they determine the breakdown voltage? I guess there's gotta be a way to detect the onset of avalance without damaging the diode.


--- End quote ---
Read somewhere (usenet?) that back in the day silicon diodes would fail catastrophically at overvoltage. Controlled avalanche diodes are bit later improvement.
https://groups.google.com/forum/#!search/controlled$20avalanche$20diode$20series/rec.radio.amateur.homebrew/XLRgaCb7XQE/tO2M_k_fleYJ
taydin:
I just wanted to revisit this with new information.

Earlier, I had done a ramp test to 2.5 kV on a 1N4007 diode with a series 10 MΩ resistor. The diode had failed at a voltage about 2 kV and later measurements showed that the diode had permanently degraded. So my conclusion at that time was that, even with a series resistor, a high enough voltage causes the diode to fail.

But there is more to this story and that statement isn't correct. When looking at the datasheet of 1N4007, the worst case leakage current is specified to be 50 uA (at rated voltage and 100 degrees celsius temperature). This means that the manufacturer guarantees that the diode will NOT GET damaged under these conditions.

But when I made the ramp test, at 2 kV, with a 10 MΩ resistor, the resultant current is 200 uA, well beyond the 50 uA that the manufacturer specifies. If I had used a 40 MΩ resistor, the diode would not have failed at 2 kV.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod