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Old 17th July 2012, 01:50 AM   #1
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Default capacitor rating

i have some shizuki motor start oil cap rated 400Vac, wondering if they are safe to take working voltage of 500VDC?
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Old 17th July 2012, 11:15 AM   #2
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Originally Posted by commstech View Post
i have some shizuki motor start oil cap rated 400Vac, wondering if they are safe to take working voltage of 500VDC?
Great Question. I do not know. I know that for fuses and for switches, Usually the AC can be multiple times higher than dc, due to arcing, as for caps, I don't know, aaaaannnddd you are wanting to use are higher voltage too?
Not sure if it is a good idea.

I hope some else can help you

Btw, you have not advised of its capacity... how many uF or nF is it? What type of circuit are you planning on using it in. Will it be seeing a high current, or low current, will it be audio or electrical work?

Options - options, so many things to consider.
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Old 17th July 2012, 01:44 PM   #3
marce is offline marce  United Kingdom
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Nope, cap ratings are best when over rated, so for those caps I'd go for 200V max.
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Old 17th July 2012, 02:09 PM   #4
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No, use at least 630VDC.
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Old 17th July 2012, 05:58 PM   #5
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No, use at least 630VDC.
Sorry, not too sure what you are trying to say.
Are you saying that 400VAC rated caps are good for up to 630VDC?
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Old 17th July 2012, 06:07 PM   #6
fpitas is offline fpitas  United States
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Quote:
Originally Posted by commstech View Post
i have some shizuki motor start oil cap rated 400Vac, wondering if they are safe to take working voltage of 500VDC?
I'd be very surprised if it couldn't handle the peak voltage of the AC as DC; the peak is 1.4 X 400 = 560V. At least for these film caps, the DC rating is far greater than the AC peak:

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Old 17th July 2012, 06:16 PM   #7
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400 VAC caps are good for at least 560 VDC. RMS times 1.414
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Old 17th July 2012, 06:27 PM   #8
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Quote:
Originally Posted by commstech View Post
Sorry, not too sure what you are trying to say.
Are you saying that 400VAC rated caps are good for up to 630VDC?
400V * 1.414 is about 566V, so the nearest standard value is 630VDC (at least in Argentina).
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