[Amps] For cats sake!

[Will Matney]

Bill,

It's according to how you hook it up. If you connect one end of the variacs winding to the line, and the output to the wiper (going to the load), leaving the other side of the variacs winding unconnected, you have a variable choke. All it is, is a round iron core toroid, with magnet wire wrapped around it, and a wiper running across the bare magnet wire on the back side. If you use both ends of the coil (both to the line), and the wiper as out, you have a variable autotransformer. It will work either way. Generally, I always use them as a variable choke, and have ran several motors that way by converting the output AC to DC with rectifiers, and hooking that to a DC PM motor. All you have then is a big variable voltage DC supply. The old Hobart mig wire feeders worked the same way. That's how I powered my winding lathe too, and worked like a charm. In his case, he could use a choke to drop the line voltage some, however it will raise the current in the primary. He can use it on the secondary side too providing the wire and paper in the choke can stand up to the HV (if it's insulated enough). Last he could buck the HV winding with a transformer that has a secondary of the right value. I personally don't like that route though because of the expense. A choke or variac is most likely cheaper than a transformer.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 3/5/06 at 7:49 PM Bill Turner wrote:

>ORIGINAL MESSAGE:
>
>At 04:45 PM 3/5/2006, Will Matney wrote:
>>That or a choke with enough inductive reactance to drop the voltage 
>>as that's all a variac is.
>
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Can't believe you said that, Will.
>
>A variac is a transformer, not a choke. With a choke, the amount of 
>voltage drop depends on the amount of current drawn, while with a 
>variac it does not.
>
>73, Bill W6WRT
>
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