Re: MMC from Microwave Caps

["Tesla list" <tesla-at-xxxxxxxxxx>]

Original poster: "bob golding" <yubba-at-clara-dot-net> 

Hi Alan,
	One or two problems with using MOT caps. The first problem is that they
are only really designed for 50/60 hz. The other problem is that all the
ones I have looked at contain internal high value leakage resistors for
safety. If you have the diodes and the trannys I suppose you could try
making a DC supply. Lot of trouble though. Hope this helps. 

cheers 
bob golding

Tesla list wrote:
> 
> Original poster: "Kelly & Phillipa Williams" <kellyw-at-ihug.co.nz>
> 
> Hi All,
> 
> I had an idea for a cheap 'MMC' using microwave capacitors.
> 
> The capacitors are 1 uF, (1 E -6 Farads)
> If I put 20 caps in series, (one string)
> the voltage rating would be a whopping 40 kV *RMS* or 56 kV DC!!
> (Assuming the faceplate voltage of 2000 VAC)
> 
> The capacitance would be 50 nF (0.05 uF)
> 
> At first glance, this seems like a great MMC, but there are a couple of
> problems I have
> thought of.
> 1) I remember someone telling the list that these caps have small internal
> leads and thin
>       plates, perhaps limiting their current discharging capability
> 2) Their dv/dt (Volts per microsecond) may not be high enough for TC use
> 3) Due to tolerances, the voltage stress on each cap may be unequal, leading
> to early failure.
>     (although the voltage rating of the whole cap is very high)
> 4) One string of caps may not be able to handle the current stresses
> 
> I have 23 microwave capacitors.
> I'd really like to be able to do this, (as it's free,) and I'm desperate for
> a cap for first light
> so I can spend some time thinking about what I want to buy for a more
> traditional MMC,
> as it will cost me quite a lot of money (for a student).
> 
> *Does anyone know of any problems with this idea, or can confirm my
> thoughts?*
> I don't care if the caps die in a few hours, I got them free.
> 
> Thank you very much,
> 
> Alan Williams