Re: SCR based coils (was High-Power Car Ignition Coils)

Tesla List wrote:
> Original Poster: "Bill the arcstarter" <arcstarter-at-hotmail-dot-com>
> Eddie Burwell <eburwell-at-HIWAAY-dot-net> wrote:
> >I've been working on an SCR based coil for a while now and hopefully
> soon I
> >should be posting a webpage about it. My number one resource for design
> has
> >been:
> >
> >SCR Manual
> >Sixth Edition
> >General Electric
> >
> >I belive it's available through amazon-dot-com.
> >
> >I also have found the Powerex SCR databooks to be of use.
> >Check out www.pwrx-dot-com
> Unfortunately the GE SCR manual appears to be out of print. :(
> I'm trying to do phase control of an inductive load (welder).  See the
> following circuit:
> http://www.geocities-dot-com/CapeCanaveral/Hangar/6160/temp/triac.html
> The question is how to size the gate resistor.  Too large a resistor
> won't allow a quick turn-on of the part, but too small a resistor would
> allow a possibly large gate current.  This problem appears to be
> aggravated by the fact that the voltage across the resistor depends on
> the firing angle.
> If anyone has any comments on that - I'd love to hear them.  My present
> design is less than reliable. :(  I'm not sure if I've been starving the
> gate or not.
> (The circuit doesn't show the 100 ohm 0.1 uf snubber which is attached
> across the triac terminals)
> Now I know why most industrial designs use a small pulse transformer
> between the cathode and the gate - rather than shunting current from the
> anode into the gate...
> -Bill

Bill and all,

I've got a some Servo drive schematics. These circuits switch SCRs at a
fast rate.  (Bill), I also have some servo drive packs , (for dc motors,
PWM type). If you are interested you can have them, (free as usual). I'm
still holding the pig stand for you, but it is now frozen to the

If others on the list are interested in SCR schematicse-mail me off the
list and I'll attempt to send out a copy.  


Cliff Fahrer