Re: Tiny DRSSTC completed

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "colin heath" <colin.heath4@xxxxxxxxxxxx>

hi sue,
        i have used those chips upto 2.5MHz ! albeit they were driving an
irfp460 and would fail now and then.
so i think 600khz should be fine. in fact i ran a half bridge of irfp460s at
this exact frequency this year.
although thats not driving the huge capacitance of those mini bricks
cheers
colin

----- Original Message -----
From: Tesla list <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, December 07, 2004 1:04 AM
Subject: Re: Tiny DRSSTC completed


> Original poster: Sue Gaeta <sgsparky@xxxxxxxxxxx>
>
> Hi Steve,
>
> I wound a coil with 36 awg wire, and I know that that is quite an
> accomplishment all by itself, congratulations!
>
> Could it be that your driver chips really don't like operating at that
> frequency? I swept mine (H bridge supply off), starting around 100KHz, and
> as I got higher in frequency, the driver supply current would increase and
> the ICs would run hot. When I got to around 400 KHz, I saw the current
rise
> above an amp and I quickly shut it off! I was afraid that Chernobyl would
> happen before I had time to crank the pot the other way again!
>
> I notice that people tend to worry about whether the IGBTs can handle the
> high frequencies, but don't think about the frequency limitations of the
> driver.
>
> Sue
>
> Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: Steve Ward
>
> Hey everyone,
>
> I built this super cool little coil over the past few days, its a very
> small DRSSTC. You can read all about it here:
>
> http://www.stevehv.4hv.org/drsstc.5.htm
>
> Thats my new site by the way... though its not close to being done yet.
>
> http://www.stevehv.4hv.org/
>
> Anyway, this little guy is running at 350khz, and thats due to the use
> of 36awg!! You know, the stuff that is impossible to see with the
> naked eye unless you are within 6" of it. Even this tiny coil has a
> DC resistance of 200+ohms.
>
> So far ive blown a few things. First to go were some gate drivers,
> not sure what i did wrong but they werent happy and got really hot
> (this was during the prototype stage). The spec sheet says they arent
> supposed to latch up, but i think that is exactly what happen s, and it
> seems to be a rare event that i cant explain. Secondly i welded my
> power switch shut. I guess it didnt like the inrush current from
> charging the voltage doulber caps instantaneously ;-), i now have a
> soft start setup... no more problems. Finally, i blew my bank of
> little 1600V PP caps i was using for a MMC. Not sure if it was the
> current or the voltage that did them in, but i noticed the performance
> dropped off considerably, and these caps were super hot. Now they
> read 20% lower than they did just earlier today! That is, they were
> at 51nF, now its down to 42nF... that certainly is not good. Replaced
> them with the good old CDE 942C series caps, 3 x .15uf in series...
> shouldnt have any problems there :-). And im happy to report that NO
> IGBTs have been sent to the trash can as of yet :-), then again i
> think i can squeeze 18" sparks out of this setup, so we will see what
> happens as i try to reach that goal. I can smell the burning silicon
> already...
>
> Seeya,
>
> Steve
>
>
>
>