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Author Topic: Capacitor voltage rating question  (Read 2101 times)

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Offline krichTopic starter

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Capacitor voltage rating question
« on: October 30, 2007, 05:08:18 PM »
I've got a number of capacitors laying around from a previous project.  The catch is that they are rated for 250V, for example.  I know the recommendation is to use a cap rated at about twice the voltage you are expecting to run through it, but is there any issue with using a capacitor that is rated at 20 or more times the voltage?   ???

These guys are left over from a monitor repair I did a while back, thus the larger voltage ratings.


Offline frank26080115

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Re: Capacitor voltage rating question
« Reply #1 on: October 30, 2007, 05:44:13 PM »
i've actually read that you need to be over the rating by at least %50, too high a rating will cause it not to work
i can't say for sure
« Last Edit: October 30, 2007, 06:44:41 PM by frank26080115 »

Offline krichTopic starter

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Re: Capacitor voltage rating question
« Reply #2 on: October 30, 2007, 06:36:48 PM »
What about a 240V capacitor on a 5V circuit, assuming the proper number of uF's?

Offline airman00

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Re: Capacitor voltage rating question
« Reply #3 on: October 30, 2007, 07:33:37 PM »
Why not just make a simple circuit with a switch ,LED, and capacitor?

Should take like 5 minutes...  ;)
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Offline paulstreats

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Re: Capacitor voltage rating question
« Reply #4 on: October 30, 2007, 07:38:52 PM »
There should really be no problem in using a higher v rated capacitor, ive used a 25 kilovolt cap on a 24 volt circuit (although i did change it eventually once i got a suitable one), the load might alter slightly though

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Re: Capacitor voltage rating question
« Reply #5 on: October 31, 2007, 07:26:09 AM »
That 250V rating is actually for AC current (its a non-polarized cap, like ceramic, right?) . . . I don't remember what the conversion is, but I think its like 100V for DC.

For crude applications (like for motors) it won't matter.

The only real disadvantage to a voltage rating that high is that the capacitor is unnecessarily large.

Offline krichTopic starter

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Re: Capacitor voltage rating question
« Reply #6 on: October 31, 2007, 09:59:38 AM »
That makes sense.  I just got around to looking at some of the ratings and what you say about the size is definitely true.   A good example is this 350V 22uF capacitor.  Its a tenth the uF's as the one used in the $50 dollar robot, but its at least 5 to 6 times larger (wow).

Edit:  These are polarized caps.  I guess there's some high DC voltage flying around inside a monitor.
« Last Edit: October 31, 2007, 10:04:25 AM by krich »

 


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