[AMRadio] Variac hook up

[Donald Chester]

>From: "Steve Fitzgerald" <stevef at gte.net>
>
Can I assume that 1 and 2 are input and 3,4
>are output?

I would be careful.  You don't want to risk connecting it up wrong and 
burning out the winding.  Most variacs have taps that allow the output to 
either go from 0 to full line voltage, or to go  from zero to about 20% 
above full line voltage.  The taps are located near the end of the winding.  
Some units have a similar tap on each end of the winding to accomadate the 
type of moutning, or if the voltage output increases when it is turned 
clockwise or anti-clockwise.

You don't want to accidently apply full line voltage between the end of the 
winding and the tap that is near that end.  I would measure the resistance 
between taps using every combination, and apply initial voltage between the 
taps with the highest resistance.  Use a 75w light bulb in series with the 
110 volt source for the initial test, to limit current in case you 
inadvertently hook things up wrong.  You should be able to determine which 
terminal goes to what tap that way.  Don't remove the bulb until you are 
absolutely certain you have the taps figured out.

In case you see gibberish below, I tried to draw a diagram.  I hope it comes 
out the same way as it looks on my screen.

>hot here for 0-110v________                                    (
>hot here for 0-140v________(
>                            (<-------- output (variable tap)
>                            (
>                            (
>       neutral here_________(_________ common
>                            (
>                            (






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