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