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Message-ID: <F7B9921A84EC44109280CD5B3AD3C989@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <CAKvcm2cwyEg8XqiD6S4cd9B1eBVdte4vY7xU2O-i5NFrODmgjg@mail.gmail.com><FDABFB388E084344A2416074AE8C2EAB@gnat> <CAKvcm2dedDktzC2Y-d=nYDhqNeU3Kpn7CFxy9-9EyEdvHcUs7w@mail.gmail.com>
Date: Thu, 9 Aug 2012 10:28:28 +0100
MIME-Version: 1.0
Subject: Re: LF: Re: Caps for Class-E amp
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Hi Dimitrios, yes those should do the job. I suppose that you need a 
situation with paralleled caps where any one can carry the peak current. It 
is probably a bit marginal if you really have to rely on current sharing in 
this situation. I used up to 3 in parallel in the C2 position without 
problems....I seem to remember the peak current was about 15 amp. I did a 
simulation usig a switch mode power supply model.
Good Luck with it.
Alan
G3NYK

----- Original Message ----- 
From: "Dimitrios Tsifakis" <dtsifakis@gmail.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Thursday, August 09, 2012 1:34 AM
Subject: Re: LF: Re: Caps for Class-E amp


> Hi Alan,
>
> thanks for the tip, I will keep an eye open for RIFA PHE428 or PHE450
> which seems to be the newer version of that capacitor type.
>
> In my PA, I used two .1 uF caps in series to make .05 uF, then three
> of these in parallel to make .15 uF hoping that the currents will be
> distributed, however I think, once one of them gave up the ghost, the
> others immediatelly followed suit, so I ended up with one in every
> two-in-series capacitor being busted.
>
> By the way, that self-healing effect is quite useful if you ever want
> to create a bunch of lower value caps with non standard values :-) I
> now have a77 nF, 45 nF, 16 nF and even a 0.3 nF out of my .1 caps! I
> am kidding of course. :-)
>
> 73, Dimitris VK1SV
>
> 2012/8/9 Alan Melia <alan.melia@btinternet.com>:
>> Hi Demitris, I am not sure of the types codes but I used 1000v or greater
>> rating, the problem often is that the caps are not rated for high pulse
>> currents. The best kind of caps that are used are rated for pulse 
>> operation
>> in switch-mode power supply. Normal caps will not take the current
>> pulses.....the individual plates get disconnected from the lead wires.
>> One of the caps I used has come to hand its a RIFA PHE428 rated 2000v. I
>> used this on 36v Class E running about 300W. I believe WIMA make similar
>> caps but I am not sure of their type numbers.
>>
>> Alan
>> G3NYK
>>
>> ----- Original Message ----- From: "Dimitrios Tsifakis"
>> <dtsifakis@gmail.com>
>> To: <rsgb_lf_group@blacksheep.org>
>> Sent: Wednesday, August 08, 2012 11:03 PM
>> Subject: LF: Caps for Class-E amp
>>
>>
>>> Hello LF group,
>>>
>>> I am building a 200 W Class-E transmitter for LF but keep killing the
>>> capacitors in the output circuit (both C1 and C2 according to the
>>> schematic in  Sokal's QST article). I have used a mixture WIMA
>>> polypropylene MKP10, MKP4 and  FKP1 caps and I haven't damaged any FKP
>>> ones so far. Should I not bother with MKP and use only FKP caps or is
>>> there any other type of capacitor what will do the job? I need a
>>> couple of hundred of nanofarads. The voltage rating of the caps I
>>> destroyed was 400 VDC or 250 VAC. I can see that these caps have a
>>> decreasing AC rating as the frequency goes up, but that's what I had
>>> in the junk box at the time...
>>>
>>> The mode of failure of these MKP10 0.1 400 VDC caps is interesting
>>> too, they seem to go down in capacitance as the damage progresses.
>>>
>>> Any advice is appreciated.
>>>
>>> 73, Dimitris VK1SV/SV1DET
>>>
>>
>>
>