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MKP X2 caps

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LAN_403

raff

Thu Feb 25 2010, 02:22AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

guys,

I have a few if these caps.. I use it on my IGBT halfbridge as DC blocking caps...
can these capacitors be used for DR especially for primary LC tank?

-Ralph

teravolt

Thu Feb 25 2010, 03:19AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

whhat type of caps and value are they

raff

Thu Feb 25 2010, 06:35AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

THESE caps found on PC PS or PC monitors.. common values are 0.1uF 250V or 275V , .33uF , and 0.47uF...

of course I have to series-parallel them for capacitance and voltage

so.. can they?

Luca

Thu Feb 25 2010, 08:09AM

Registered Member #2481 Joined: Mon Nov 23 2009, 03:07PM
Location: ITALY
Posts: 134

Given the rating voltage of that caps you need to put a lot in series...

Also, I think that X2 caps are not designed for high currents (both rms and pulsed) since they are used "accross the line" for EMI filtering...

You can try, but I think that they will burn quite soon...

Luca

mmt

Thu Feb 25 2010, 08:30AM

Registered Member #2333 Joined: Thu Sept 03 2009, 03:04PM
Location: Slovakia
Posts: 80

i have used these for some smaller TCs, they works fine..

Dr. Dark Current

Thu Feb 25 2010, 08:32AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

They usually work fine for pulsed or high frequency/current applications, but I have come across a few which heat up a lot more than the others for some reason.

Herr Zapp

Thu Feb 25 2010, 09:06PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

Raff -

You may be confusing your dielectric materials ..........

You titled this thread "MKP X2 caps", but the only designation I can see on any of the caps in your photo is "MKT".

MKT and MKP are completely different dielectric materials, with very different high frequency loss factors (dissipation factor = dielectric heating at high frequencies).

MKT represents a metallized polyester film dielectric. This material (one trade name is Mylar) is fine for use at 50-60 Hz, but it can quickly overheat and fail at 100-400 KHz, a range of frequencies typical of small-medium Tesla coils.

MKP represents a metallized polypropylene film dielectric, which has much lower loss factor than MKT and can be suitable for use at higher frequencies.

However, in addition to having the correct low-loss dielectric, a capacitor's ability to handle high pulse current is crucial to being able to survive in a TC tank circuit. Unfortunately, most of the commonly-encountered "X capacitors" use metallized film construction, which cannot handle really high pulse currents. What you really want are capacitors using polypropylene dielectric with foil electrodes, like the CDE 942 series, the WIMA FKP series, etc. The "F" in FKP represents "foil" electrodes, vs the "M" representing metallized film in MKP capacitors.

Capacitors using foil electrodes can handle much higher pulse currents than metallized film electrodes can. The MKT caps will overheat internally and die, and with both the MKT and MKP capacitors the end connections between the leads and the edges of the metallized film can burn away and the caps will die.

Regards,
Herr Zapp

raff

Thu Feb 25 2010, 11:57PM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

Herr,

thanks for that info .. that MKT shown, I only got one.. most of what I use are MKP.. I havent used that for primary LC tank(I use a diy rolled one, as shown in my smalll drsstc), though I have successfully used them in half-bridge drivers..as DC blocking caps .... or I could eliminate them if I where to go full-bridge

-Ralph

Kipmans

Fri Feb 26 2010, 12:14PM

Registered Member #91 Joined: Thu Feb 09 2006, 03:03PM
Location: The Netherlands
Posts: 45

Also, there are of course different types of MKP capacitor. WIMA, for example, has the MKP4 and the MKP10 series, with the latter being more suitable for pulse applications (altough they are obviously not as strong as the FKP series).

I have succesfully used MKP4 caps in a small SSTC halfbridge and will be using MKP10 as coupling capacitors for my next full bridge. However, since I have no DRSSTC experience yet, I can't say how they will perform in an LC tank circuit. I'm guessing it all comes down to the power level you're planning on using...

raff

Sat Feb 27 2010, 10:07AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

Hi
Yes having WIMA or CDE caps are great BUT too much of a hastle ordering them(unless you got credit card) w/c obviously I dont have... anyways, Im quiet happy how my MKP X2 caps are with my half-bridge inverter... gets warm a bit... next best option is go fullbrige.. anyways, Im currently redesigning it AOTM

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