Re: Problems & DC drive solutions

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

Original poster: "Steve & Jackie Young by way of Terry Fritz <twftesla-at-uswest-dot-net>" <youngs-at-konnections-dot-com>

Kevin & other DC coilers,

I had a look at your schematic, referenced below.  Have you considered
connecting a reservoir capacitor, of 1-10 Mfd at 18+KV at the output of your
bridge to ground?  This would then feed the rest of your circuit, except you
could then get rid of the power wasting power resistor.  This would insulate
your HV diodes from the large current when your gap fires because the
reservoir cap would supply the large instantaneous power and your diodes
only have to handle the average current to the reservoir cap.  The only
thing to watch out for is blowing the diodes by not slowly ramping up the
power to your potential transformer.  (Note, the reservoir cap makes the
circuit even more potentially deadly - be very careful if you try this)!

Your thoughts?
--Steve
----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, January 07, 2001 3:04 PM
Subject: Re: It's Me Again, After a Long Recess, and I've got problems...


> 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.
<SNIP>