As already pointed out, for a current limiting ballast transformer, the
secondary coil will be shorted out, and the primary will be in series with
the load.
However, I have been wondering what would happen if you put a (variable)
resistor on the secondary side of the ballast transformer (instead of a
dead short). I wonder if this would give you some degree of variable
current limiting? From all my reading, it seems like the best current
limiting uses BOTH inductance and resistance...so I wonder if resistance
located in this location would work.
~Dan
On Mon, Jun 4, 2018 at 8:03 PM, David Rieben <drieben@xxxxxxx> wrote:
> Ronald,
>
> Welding transformers obviously must be designed to withstand a very low
> impedance short circuit across its secondary output winding (within a
> reasonable duty cycle) when the welder strikes an arc with it. Therefore,
> shorting the secondary (work) winding while the primary input is in series
> with the primary of the step up transformer is actually staying pretty much
> within the design parameters of the welding transformer - especially when
> you consider that most coiling is also done on a very limited duty cycle.
>
> David
>
>
>
>
> ----- Original Message ----- From: "Ronald Reeland" <ronreeland@xxxxxxx>
> To: "TESLA COIL MAILING LIST PUPMAN" <tesla@xxxxxxxxxx>; "Ronald Reeland"
> <ronreeland@xxxxxxx>
> Sent: Monday, June 04, 2018 3:58 PM
> Subject: [TCML] Welding Transformer As Ballast or Choke
>
>
>
> Hi:
>> I am trying to understand how a welding transformer functions as a
>> ballast choke to limit surge current thus preventing circuit beakers
>> tripping. I get the fact that the welder has a heavy gage winding and can
>> handle high currents. And it has a certain inductance figure that presents
>> inductive reactance at or impedance at 60 Hertz to changes or surges in
>> current. But I am baffled as to why the welder has its secondary side
>> shorted out when used as a ballast choke.
>>
>> A basic transformer has its highest impedance or inductive reactance on
>> its primary when there is no load on the secondary. As the secondary load
>> increases, primary reactance decreases and primary current increases. So if
>> you short the secondary, that is maximum load causing the primary reactance
>> to greatly decrease thus raising the primary current to a maximum. ( And
>> burning up the transformer as a result.)
>>
>> So it seems to me that an unloaded secondary is the best situation while
>> using a primary as a choke coil.
>>
>> And yet, Tesla coilers seem to get best results with a shorted secondary
>> on the welding transformer. Please explain.
>>
>> Thanks,
>> Ron Reeland
>> _______________________________________________
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>> Tesla@xxxxxxxxxxxxxxxxxx
>> https://www.pupman.com/mailman/listinfo/tesla
>>
>
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