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Re: [TCML] Welding Transformer As Ballast or Choke



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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