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Capacitor Size Matter?


stealth17
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A larger new capacitor has a better ripple-current rating.
If the capacitor is used as the rectifier filter in a high current power supply, It will have a high ripple voltage across it because its charging and discharging currents are high. A small capacitor will overheat and fail. You might need to use a large capacitor with a higher voltage rating to find one with a high ripple-current rating.
Large old capacitors have about the same ripple-current ratings as small new ones, so don't just select a larger size.

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A larger new capacitor has a better ripple-current rating.
If the capacitor is used as the rectifier filter in a high current power supply, It will have a high ripple voltage across it because its charging and discharging currents are high. A small capacitor will overheat and fail. You might need to use a large capacitor with a higher voltage rating to find one with a high ripple-current rating.
Large old capacitors have about the same ripple-current ratings as small new ones, so don't just select a larger size.


cool, thanks. Ive read that its not a real good idea in most cases to go over 150% original capacitance. The voltage doesn seem to matter either. Like I can use a 25v cap in place of a 10v cap without problems. Also Ive read that the low-ESR caps are the ones rated for 105c (usually).

Sound all up to par?
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Hi Prateek,
Large value capacitors are usually used as filters following a full-wave rectifier in high current equipment. Surges are infrequent but ripple current occurs continuousy, on every half-cycle of the mains. Because the load current is high, the capacitor's ripple current is also high which overheats small capacitors.

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