Capacitor Frequency Rating

Does the frequency rating on some AC capacitors really matter that much as long as the current rating isn't exceeded? I have some capacitors that have 50/60Hz marked on them, but I'm not sure how a capacitor can have a limited frequency, especially at such low levels. I want to use them in resonating circuits where they'd be exposed to frequencies from 30kHz to 50kHz or 100kHz to 200kHz, depending on whether I choose to use IGBTs or MOSFETs as my switching devices.

What are the capacitor part numbers or the dielectric type?

Do the capacitors have an RMS current rating high enough for your circuit and are they operated within their di/dt ratings?

There are three specific ones that I have that I want to use for this circuit. They're from microwaves, and I think they're motor start or motor run capacitors for powerful fans. They look like black, rectangular boxes with some kind of flange with a hole for mounting. I'm not sure what the current or di/dt ratings are. I tried looking for the fan motors to check their rated current pull, but I couldn't find them. Unless I find them or find ratings online, I would assume their good for 1A. If these seem to be able to handle a decent di/dt, then I would use them in the circuit and adjust the circuit to change the current. The circuit is for either a small induction furnace or inductive levitator. The three capacitors have the following printed on them:

SH.CAPACITOR
250V~50/60Hz
6uF(-5%~+10%)
25/85/21.PO.ClassB
DMB-S2EJ006
DONG GUANG DAE YEONG

DAE DONG
10uF +10% -5% E214947
220VAC 50/60Hz
-25/70 degrees C DMF

OH YOUNG
10uF +10% -5%
220 VAC 50/60 Hz
-25/70 degrees C
YMR 22106
0509A

I could not find datasheets and so I can't say much about the suitability of these. If it's a home project why not try them?

If you want to order new caps with datasheets Digikey has a good stock. An example is the metalized polypropylene Vishay MKP386M530125YT4, with specs of 3uF,450 VAC, 16.5 A RMS, 4 milliohm ESR.