Our of curiosity I ran a Hi-Pot (High Potential Breakdown) test on several FT-1 and K40Y capacitors. The test was performed with an AR 3570D Hi-Pot II test set which is in calibration. Test was performed at room temp without baking the capacitors first.
The FT-1 were 0.022uF 200V rated, the K40Y were 0.1uF 630V rated.
Caps were consistent in their breakdown voltage at 100uA, with the FT-1 caps breaking down above 1.1KV and less than 1.2KV, and the K40Y caps breaking down above 2.1KV and below 2.2KV
I have another 10 FT-1s on order to test, but they won't be here for three weeks or so.
I think I'll try testing some Orange Drop caps next to see where they break down.
These margins are much higher than seen with Al Electrolytics, but considering the difference in dielectric that is not surprising.
The FT-1 were a bit surprising to me, but it is possible they were made with the same dielectric as higher voltage versions simply to minimize stock materials.
I need to get some samples of higher voltage rated FT series caps to see if they show the same margin.
The FT-1 were 0.022uF 200V rated, the K40Y were 0.1uF 630V rated.
Caps were consistent in their breakdown voltage at 100uA, with the FT-1 caps breaking down above 1.1KV and less than 1.2KV, and the K40Y caps breaking down above 2.1KV and below 2.2KV
I have another 10 FT-1s on order to test, but they won't be here for three weeks or so.
I think I'll try testing some Orange Drop caps next to see where they break down.
These margins are much higher than seen with Al Electrolytics, but considering the difference in dielectric that is not surprising.
The FT-1 were a bit surprising to me, but it is possible they were made with the same dielectric as higher voltage versions simply to minimize stock materials.
I need to get some samples of higher voltage rated FT series caps to see if they show the same margin.
In the distant past we would do the same thing. We had the Hi-Pot out to check other components and with some time to spare we checked some capacitors multi-conductor signal wire. Even low voltage parts will take 1 KV without breakdown.
Yes it sometimes happens but very often, low voltage parts (not E-caps obviously) can take a huge level of abuse: I remember 63V mylars that consistently refused to breakdown at 500V.
On the other hand, "real" HV parts tend to be much less generously dimensioned: if you test a 2kV cap at 3kV, it will probably survive, but I wouldn't bet on 4 or 5kV (except if it is some kind of Hi-rel/safety cap)
FT-2s came in. 0.1uF 5%, 200V rating.
Most of the Caps showed 0.12mA charging current and then 0.00ma leakage at 2000V for one minute.
Out of ten capacitors, two failed.
One reached 2KV and held for 8 seconds before breaking down.
This cap is now shorted.
The second failed at 1800V on ramp up. It now passes hipot at 600V for one minute with less than 0.00mA leakage. If I test at 1000V it passes for several seconds and stats leaking above 1mA.
Most of the Caps showed 0.12mA charging current and then 0.00ma leakage at 2000V for one minute.
Out of ten capacitors, two failed.
One reached 2KV and held for 8 seconds before breaking down.
This cap is now shorted.
The second failed at 1800V on ramp up. It now passes hipot at 600V for one minute with less than 0.00mA leakage. If I test at 1000V it passes for several seconds and stats leaking above 1mA.
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