Re: Off-Line Tesla coils (OLTC)

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>



Tesla list wrote:
> 
> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
> 
> Hi All,
> 
> Today I substantially rethought the front end of my off-line Tesla coil.
> The schematic is at:
> 
> http://hot-streamer-dot-com/temp/Image1-1.gif
>
> 3.      The BPS rate can arbitrarily be anything the rest of the circuit
could
> support.  Since it is now a true DC charger, there is no need to worry with
> 60 or 120Hz BPS rates.  It is far simpler theoretically now that the old
> way which was tuned to the line frequency.

Don't you need a diode in series with L35 and L34, as in a typical resonant
charging circuit..

There's also no need for both L35 and L34 (since they are in series.. and
the same goes for R63 and R64)  just one 20 mH choke and 1 40 ohm resistor
should do it.

OTOH maybe you've got the components sitting around...


> 
> 6.      The IGBT really does not care if you increase the BPS rate, so
nothing
> else really changes.  You may be able to go to a smaller primary cap to
> increase the Fo frequency.  Its value no longer depends on the input circuit.
> 
> 7.      The primary tank circuit is no longer loaded by the charging circuit.
> That allows more and cleaner energy and more power throughput.
> 
> The only real disadvantage is that the two large 5600uF caps (250 joules
> each) need a lot of care.  Fusing, soft start, safety discharging, etc. is
> needed (don't wire them backwards ;-)).  The large caps values are really
> not necessary and are arbitrary, but we need HIGH ripple currents.  That
> naturally calls for thousands of uF of capacitance in common big caps.
> Ripple current is their key specification here.

The series resistors in the charging might give you soft start.... The 2
ohm ones you've got will limit the current to around 100A, and the caps
will charge quickly.  Granted the little 1Amp 1N400x rectifiers might pop,
but an off the shelf 25-40Amp 600PIV bridge (use only half) probably has a
healthy enough Isurge that it would work.  Or, a couple of stud mount diodes.  

Another trick is the "100W light bulb in series" one (probably about 10
ohms, cold), or a relay/resistor soft start.



> 
> Cheers,
> 
>         Terry
> 
> >Hi All,
> >
> 
>