400V cap on 24V rail

[cupoftea]

Hi,
We have a linear regulator, 32Vin to 24Vout at 5A.
It has a 400V 10nF Cap at its output, in parallel with a 3.3mF, 35V lytic.
The 400V cap is Vishay MKT1813 series.....

MKT1813

https://www.mouser.co.uk/datasheet/2/427/mkt1813-1761985.pdf

Why has this cap been used?
Does it form properly with just 24V across it?

 

[dick_freebird]

Film, ceramic or any plain dielectric capacitor (i.e. not "wet",
like tantalum or aluminum electrolytic) should have no
"forming" need or mechanism. "Forming" means sealing
any pinholes by further anodizing.

An electrolytic will not respond to fast high pulses due
to its inductive (spiral) construction. Maybe this little HV
cap is an ESD thing. Or maybe they already had it in the
parts system and just used it because it had an OK value,
and voltage "premium" costs nothing in this specific case.