Re: HELP WITH TOROID

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: David Speck <dave@xxxxxxxxxxxxxxxx>

Drew,
I can't offer any suggestions about the toroid, but I'd offer the following 
on the power control switches.

For systems at power levels that you describe, you usually don't switch the 
50 amp currents directly from the front panel.

Instead, you use low voltage front panel switches, typically 24 VAC, to 
drive heavy duty relays, often called contactors, appropriately rated for 
the current you intend to draw, and with a sizable safety margin to boot.

Look on eBay under Allen-Bradley, Cutler Hammer, or Square-D for industrial 
front panel switches and pilot lights of many different configurations to 
fit your needs.  Prices for these can often get pretty high, but 
frequently, pieces fall through the cracks and can be bought very reasonably.
A search for "contactor*" or "power relay*" will bring up what you need for 
power handling.  I'd avoid motor starter contactors, as they have heaters 
to detect and shut off under overcurrent situations.  They might produce 
unanticipated results in TC use.
Check your local junkyard for scrapped industrial machinery, as the front 
panels will frequently have switches like these, and you might get a better 
deal that way.  A 240 to 24 VAC industrial control transformer will provide 
the low voltage you need to run the control circuitry.
Be sure to incorporate an emergency stop circuit with an easily accessed 
big red mushroom button to kill everything in case of unanticipated 
results.  The most cautious coilers include a hand held pendant switch with 
a button that has to be held in continuously to allow any operation of the 
high voltage circuitry.
Your 10 kVA tranny would draw ~42 amps on 240V at max rating, and is 
capable of at least twice that for short runs, so you'd want a contactor 
rated at least 80 amps, if not 100.  Using an overrated contactor will save 
you from rebuilding when you move up to the next power level, and also 
reduce the possibility of having your contacts weld shut in a major fault 
situation.
HTH,
Dave

Tesla list wrote:

> Original poster: Teslamad@xxxxxxx
> I've been coiling for years now and im about to complete my latest coil. 
> This coil was built for research purposes. It runs off a 14,400 10KVA 
> X-former, but unfortunately before it will be operational, it needs a 
> toroid. I have tried building it MANY times from Home Depot ducting with 
> unsuccessful (expensive) results!!! The ducting used by other coilers 
> appears more ridged than mine... hmm... Could you please tell me where to 
> get this other material or how to handle the ducting (dentable and 
> fragile) I've been getting from home depot? Also, one other thing, where 
> do you purchase heavy duty switches for control panels and how much are 
> they (240v 50A)???
>
> Thanks,
> ~Drew