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