Imprignation

Since this is in the electrical area, it probably means 'non- polychlorinated biphenyl impregnation'.

National Pharmaceutical Control Bureau certification that the capacitor contains natural biodegradable oil....
http://portal.bpfk.gov.my/index.cfm?&menuid=146&parentid=113

Impregnation means infused with a resin, probably, in this case, I think, maybe.

bigg had it.

In electrolytic capacitors, "impregnation" is the term used for forcing the electrolyte in between the layers of the capacitive film that is used. The impregnation materials vary, but for years, a highly stable form of mineral oil was used, which was stabilized against breaking down by using additives known collectively as PCBs, Poly-Clorinated Biphenyls.

But as it turned out, PCBs were extremely dangerous to living creatures, including humans, and they are so stable that they don't break down in nature either, so spills and discards became a big building problem, identified in the 1970s and acted upon in the 1980s. For a while, the problems with using PCBs forced a lot of people in the world to ban their use, and because it was difficult to know or even test if PCBs were used in insulating oils inside of sealed devices like capacitors, specifications arose requiring that all electrolytic capacitors be labeled as having Non-PCB, or "NPCB" materials inside.

So saying that a capacitor is "NPCB impregnated" is now essentially the de-facto standard, but remains a requirement as far as stating it clearly, likely because there are people in the world who stoop to low tactics to make products cheap. There are still large stockpiles of PCB laden mineral oil that exist and cost money to store or dispose of properly, so it's been known to happen that if someone fails to specify it clearly, the low bidder uses that toxic oil to get rid of it by making it a problem for someone else.

www.acronymfinder.com/NPCB

Delete those that are inapplicable.