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Registered Member #54278
Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367
I am looking for -reliable- information concerning a safe DC voltage rating for AC capacitors. Mostly, I have seen the V*1.414 rule, or [ V x sqrt (2) ]. This is obtained, obviously, from calculating the peak value an AC signal would apply to the capacitor. So I guess there is also a peak-to-peak rule [2V*sqrt(2)] out there too.
Here are some additional comments I have run into:
The "simple textbook equation" says that an AC capacitor can take 1.414 times its AC rating with DC. However, due to AC causing extra stress to capacitors, the real-world factor is higher.
"I have seen a few capacitors with an AC rating of 1 kV and a DC rating of 3 kV. I have seen a few others with the factor being around 2.5."
"I think it's generally reasonably safe to have DC voltage at 2 times the AC voltage rating, and generally only mildly adventurous to have DC at 2.5 times the AC rating."
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
for foil/film capacitors I have noticed rated Vac = 0.4 x Vdc quite common and Vtest = 1.5 x Vdc rated, but it is better to look at manufacturers datasheet, and wiser to not use any component at maximum rated value !
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