Did you know that the new configurations using >28,000uF capacitors may need a pre-charge to prevent in-rush current from tripping the power source?

CS101 and CS117 configurations call for installation of a >28,000uF capacitor for DC powered devices.  At power on, the uncharged capacitor tends to act as a short circuit producing a significant in-rush current that may cause the power source to trip.  To help with this situation, a pre-charge circuit that controls the in-rush may be inserted to support charging the capacitor and then switching out when the charge is accumulated.  The drawing below shows a very basic pre-charge configuration – remember to use properly rated components if you decide to construct your own.

>28,000uF capacitors

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Article Reference ID: DYK00011

Posted in: Did You Know? MIL-STD-461G