Re: It works! Solid state driver (fwd)

Date: Wed, 3 Dec 1997 20:48:24 -0700
From: Don Huff <w6jl-at-e-z-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: It works! Solid state driver

Hi Max,

  CONGRATS on the encouraging work with your SS driver.  Are you using a
half-bridge?  Sounds like it (2 FETS per leg, 4 total, must be 2 legs, hence
half bridge, yes?).    1 KV AC is what you will be driving your primary
with, right?   I would think you would be running the half-bridge at
whatever frequency your primary system will be resonant at, is that right?
No rectifier, just AC square wave drive.   No spark gap, just ringing the
primary LC with an AC power source at the resonant frequency.  Am I
correctly describing what you are doing?  I am interested in this approach
if it can be an alternative to spark gaps.

  Good luck, and give more details if you can.  I am pretty familiar with
switching power supply topologies and design.

     Don, W6JL

Tesla List wrote:

> From:   RODERICK MAXWELL[SMTP:tank-at-mail.magnolia-dot-net]
> Reply To:       tank-at-mail.magnolia-dot-net
> Sent:   Tuesday, December 02, 1997 9:31 PM
> To:     tesla-at-pupman-dot-com
> Subject:        It works! Solid state driver
> I'm here to report a successful test! I have two IRF440 mosfets
> running at about 30% duty cycle on each leg for a total of four. They
> barely get warm when I crank the variac up to line voltage (no fans
> nessasary)! I think this is because of the new drivers. They turn the
> transistors on and off so quickly they don't get a chance to stay in
> transistion very long. I'm now using a 3k/50watt aluminum housed power
> resistor as load. It actually got so hot it started to BURN the plywood
> it was mounted on!! This is because I wound the secondary for higher
> voltage. I should be getting >1Kv. My current draw is way, way down from
> where it was before, about 3amps at 140vdc. I probably could increase
> the duty now.
>   Now comes the real drudgery, finishing the secondary wind wind
> wind.......
> Thanks for all your help!
>                               Frankensteins Helper
>                                       Max