Re: It's Me Again, After a Long Recess, and I've got problems...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Kevin Ottalini by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ottalini-at-mindspring-dot-com>

Ryan:
	An easy solution would be for you to convert to DC drive ...
then you can use any size capacitor that you can balance with
your primary inductor (to get to the secondary resonance).

You can also eliminate all the ballasting you are using for
the pole transformer (you still need the main variac).  The
system will be self-limiting and the current draw will be a
function of the BPS rate and your cap size.

You will need three additional components to implement this:

1.  You need a rectifier that can handle ~1amp at ~18kv
    (1.414*12,400) and should be able to handle 50 to 150amp
    peak surges.  Microwave oven diodes are an inexpensive
    source, although I know of several people who have used
    arrays of small diodes like 1N4007.

2.  You need a large wattage, non-inductive limiter resistor in the
    range of 5Kohms to 10Kohms and about 800watts (I use 4ea 160watt
    20Kohm ceramic resistors in parallel, cooled a little extra with
    a muffin fan). The resistor is there to prevent the diodes from
    suffering too large of a surge current (not to limit the power).

3.  You need to build or convert your SRSG to asynchronous (any
    speed) operation.  This can be as simple as adding a variac
    to your existing SRSG, or changing the AC motor for a DC and
    a small rectifier and a small variac.  I use a small 5400RPM DC
    motor and 8 poles with a range of about 2BPS to a max of about
    770BPS.

A complete schematic is here:
 ftp://ftp.mindspring-dot-com/users/ottalini/highvoltage/DCCOIL/DCSCH2A.PDF

Although I use a 4-diode full wave bridge, you could use a simpler
two-diode full-wave rectifier as well.

I also highly recommend that you build a simple 20KV DC meter and add 
it to your DC system.  This is easily done with a 0-20vDC, 1ma meter
movement and 20Mohms of resistance (about 20 watts worth).  This
serves two purposes:

  a. lets you see the output voltage and
  b. will discharge the capacitor bank automatically when the power
     is off.  The resistors in your MMC may also do this for you.

There is a lot of information and pics there about DC driven TCs on the
FTP site, so feel free to browse.
    (ftp://ftp.mindspring-dot-com/users/ottalini/highvoltage)

Best,
  Kevin

----------
> From: Tesla list <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: It's Me Again, After a Long Recess, and I've got problems...
> Date: Sunday, January 07, 2001 8:56 AM
> 
> Original poster: "Ryan Ries by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<spud-at-wf-dot-net>
> 
> 	It's been several months since I've posted anything to the list, but I
> have some pretty severe problems. 
> 
> 	Today is the first day that my friend and I have started working on the
> coil again in a couple months, and we have still not gotten the 10kva
pole
> pig to function correctly.  It only buzzed little 6 inch sparks.  The
> ballasting checks, the spark is decent, the primary and secondary coils
> check.  The only thing left to point at was the capacitors.  I fired up
> Wintesla, and entered in my transformer.  12400v -at- 0.81a.  It calculated
> the matched capacitance to be 0.173µf !  Is this correct?  We only have
> 0.037µf right now, and that's the highest we can get.  About a year ago,
> someone on this mailing list was generous enough to sell me some MMC
caps;
> 100 pieces for $20.  They were 0.21µf -at- 600vac.  They were the best caps
we
> have ever had, but they can't reach a capacitance like that.  As
> high-school students, neither of us have the budget to buy a capacitor
(or
> that amount of MMC caps) of that magnitude.
> 
> 	If anyone would be willing to offer any advice, I would be grateful.
> 
> 	Thanks,
> 	   Ryan Ries
> 	   spud-at-pureinsanity-dot-net
> 	   http://spud.pureinsanity-dot-net
> 
>