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| Testing 1N4007 with a megger |
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| taydin:
After the above test, I did another ramp, this time 5 kV. But the test stopped at 4.8 kV, because either the resistor broke down or the diode. Not sure which, will find out |
| taydin:
I measured the resistor, it is still 10 MOhms. And just to make sure the diode is OK, I ramped it up to like 800V and it didn't breakdown. So I suppse the resistor arced internally, but the megger shut off the voltage before the diode would get killed. The resistor is 1/4W metalfilm. |
| taydin:
So can we conclude that limiting the current prevents the junction from sustaining permanent damage under avalanche? |
| taydin:
Nope, we can't ... I picked 3 new 1N4007 from the bin and measured their insulation resistance at 1 kV. They are 65 GOhm, 87 GOhm, and 102 GOhm. Then I measured the diode that just underwent the ramp test. It has an insulation resistance of 260 MOhms ... So it has permanently degraded. |
| tooki:
--- Quote from: taydin on October 30, 2019, 09:23:52 pm ---I did repeat the test with two more 1N4007's, and the graph was quite similar. One breakdown at around 1500V, and another breakdown around 1800V. And same measurement result with the multimeter. --- End quote --- So... they all failed well beyond their maximum ratings. And this is a surprise why? Look also at the derating graph in the attached datasheet. As temperature rises, reverse current rises dramatically. --- Quote from: thm_w on October 30, 2019, 10:06:39 pm ---Do you happen to have any 1N4005/1N4006 or anything lower rated? My guess is 1N4001/2/3/4 and 5/6/7 are all the same, since the specs are equivalent. --- End quote --- Well, they can be the same, or not, depending on manufacturing method. E.g. the Vishay ones in the attached datasheet could very well just be binned dies of the same design, since they list identical specs other than breakdown voltage, while another brand's might not be. See also: https://www.eevblog.com/forum/chat/why-1n400x/ https://electronics.stackexchange.com/questions/84471/what-is-the-difference-between-1n4001-and-1n4007-other-than-their-maximum-revers |
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