SCR control

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

Original poster: "Richard W. by way of Terry Fritz <teslalist-at-qwest-dot-net>" <potluck-at-xmission-dot-com>

Hi list,

I'm gearing up to build an SCR controller. (not for tube coils)
What I'm looking for:
1) 240 VAC operation
2) Inductive load (transformers, etc)
3) Phase-Angle triggering

The "driver circuit", (pulse generation and timing) is no problem but I'm 
having a bit of trouble finding a suitable schematic for the SCRs 
themselves. I've found that the MOC3021, MOC3022 and MOC3023 are non 
zero-crossing opto-Isolators.

Below is a schematic similar to what I need except it's using the MOC3041 a 
zero-crossing unit and specifies no resistor wattages nor mentions resistor 
size in any of the text on the site/s.
Can I substitute the MOC3021 for the MOC3041 and what are the size 
resistors I need to use?
I've hunted high and low for the proper size resistors to use (wattage) but 
have found nothing. I've also bumped into "snubbers" used for triacs but I 
get the idea that snubbers may not be necessary when using SCRs.
I could be very wrong with that though.

So what I'm looking for is a schematic and/or advice for everything to the 
right of the opto-isolator as shown in the following schematic including 
the right resistor wattages. I have on hand several large SCRs made by IR 
rated at 160 amps continous. These have the extra small gauge wire for the 
cathode. (At least I think it's the cathode) and 3/4" studs part #161RM60. 
They're a bit overkill but I have them and would prefer not buying smaller 
ones.

<http://xmission-dot-com/pub/users/p/potluck/pics/SCRControl.jpg>http://xmission-dot-com/pub/users/p/potluck/pics/SCRControl.jpg

I've not only scoured the web but also searched through the Tesla List 
Archives where I found out about "hot spots" but have yet to find anything 
suitable.
Any and all input would be greatly appreciated believe me. When I close my 
eyes all I see are PDFs! LOL!!! I've been through a multitude of theory 
websites but I'm really not ready to design a complete circuit that will 
inevitably fail the first 20 - 30 attempts. :)

Thanks all !!

Rick W.
Salt Lake