Re: Microwave Oven Caps

["Malcolm Watts" <M.J.Watts-at-massey.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Tom,

On 24 Jul 00, at 19:07, Tesla list wrote:

> Original poster: "Tom Stathes" <newphreak_16-at-yahoo-dot-com> 
> 
> Hello,
>  In a series capacitor circuit the total voltage is
> the sum of the voltages of all the caps.  The
> capacitance can not be higher than the smallest cap. 

Right so far.

> In a paralell circuit the voltage can not be higher
> than the highest voltage, but the capacitence is the
> sum of all the caps.  Its just like connecting
> batteries or transformers in series and paralell. 

Not quite. The working voltage of paralleled capacitors is 
that of the *lowest* rated capacitor - if you parallel a 300V 
cap with a 150V cap, the maximum working voltage is 150V.
 
> If i were to wire up all the caps in a box, and reopen
> the oil fillhole case of each cap, then fill the box
> with oil there should be no danger of explosion
> because pressure couldnt build up right? 

No, but oil could leak out as it got warm and expanded. 
Additionally, it would be contaminated as it cooled and sucked 
air and airborne contaminants back in through the vent.
 
> Also, mabey you could help me out with this one. Or
> mabey you know someone who can.
> 
> I just wound a new primary, its a flat spiral, 20
> turns, 1/4" steel guy wire spaced about 1/4" apart. 
> The inner diameter is 7.5" My secondary is 4.5"
> diameter and 20" high (902 turns) of #24.  The tank
> cap is ~10nf (wine bottles) and the tank input is 10kv
> -at- ~133ma.  
> I can't get corona discharge of no more than 7", my
> top load is a spheroid of about 5" diameter. The first
> turn of the secondary is 1 inch above the first turn
> of the primary. Whats wrong, why do i get almost no
> discharge? Should I adjust the coupling by lowering
> the secondary a little? (I have to cut a hole in the
> base of the primary to do this and i havent the time
> to do it yet.)  

Steel is the wrong choice for your primary. It is a poor 
conductor and its ferromagnetic properties together with non-
lamination will influence secondary frequency and losses as 
well. Assuming your peal primary voltage (i.e. gap setting) is 
10kV, the per-bang energy available to the secondary if there 
were no losses would be only 0.5J which is not high. However, 
you should be able to do better than 7" with that energy so it 
looks as though there are losses you could do without in your 
primary.

> My less than spectacular other primary, (#12 wire
> wrapped on a old 12"  laundry detergent bucket
> (anything but even wire spacing)yielded sparks of up
> to 18". 

What conductor did it use?

Regards,
malcolm