Electronics > Projects, Designs, and Technical Stuff

Testing 1N4007 with a megger

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Zero999:

--- Quote from: taydin on March 07, 2020, 09:32:05 am ---
--- Quote from: mikerj on March 06, 2020, 10:29:02 pm ---If the resistor broke down then you didn't limit the diode avalanche current to the expected value.

--- End quote ---

The resistor broke down at 4.8 kV, which is way past the 2 kV point where the diode avalanched.

--- End quote ---
250µA might have been too high for the diode though.

Vovk_Z:
To resistor worked as resistor (but not as air gap) you have to obey it rated voltage.
1/4W resistor usually is something about 250V rated (300V peak).
So for your tests you need to use 4-10 series connected at least 1 W rated resistors.

rodpp:
I did the reverse breakdown voltage test on a 1N4007. My sample knee was around -1600V:



And the forward IV curve before and after the test was the same, so no damage:



If the reverse current is lower than the datasheet specification, no damage should occur with the diode.

Zero999:

--- Quote from: rodpp on March 09, 2020, 11:30:17 pm ---I did the reverse breakdown voltage test on a 1N4007. My sample knee was around -1600V:

(Attachment Link)

And the forward IV curve before and after the test was the same, so no damage:

(Attachment Link)

If the reverse current is lower than the datasheet specification, no damage should occur with the diode.

--- End quote ---
Firstly, please consider those using a lower resolution by not posting such large images and PNG is much better suited to charts, than JPG, which is meant for photographs.

Yes, you tested it at a much lower current than the original poster and just because the forward VI curve is unchanged, it doesn't mean it's not damaged. The only way of knowing that is to test the reverse breakdown voltage again.

rodpp:
Thanks for the tip about the figures.

Regarding the diode test, I did both (forward and reverse) using a curve tracer that apply a retified sin wave repeatedly. Each graph has around five half waves, but during the test was applied much more repetitions. It is clear in the reverse breakdown test graph, where it is possible to see various traces at the knee.

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