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Re: ballasting
This wouldn't be a bad place to start...
Most older welders (i.e. non solid state PWM supply types) use a variable
amount of leakage inductance in the transformer to create the correct V/I
characteristic to produce a stable arc (i.e. the arc has a negative slope
V/I, so you add a series impedance (that is, the leakage inductance) that
has a positive V/I characteristic to compensate).
Often, this takes the form of a magnetic shunt that slides in and out driven
by a knob or lever..
-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Wednesday, May 10, 2000 9:07 AM
Subject: R: ballasting
>Original Poster: "Daniele Bortoluzzi" <dbortoluzzi-at-sogeda.it>
>
>Tnx Cabbot,
>
>I also read about welders as limiters...
>There is a industrial scrap place near home that always have LARGE
>welders...
>I would like to dismantle one of these to recover the variable
>transformerand parts and use them to build a variable inductive load. I
am
>going the right way ?
>
>Ciao a tutti
>
>Daniele
>-----Messaggio originale-----
>Da: Tesla List <tesla-at-pupman-dot-com>
>A: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
>Data: mercoledì 10 maggio 2000 2.54
>Oggetto: Re: ballasting
>
>
>>Original Poster: "Cabbot Sanders" <cabbot-at-hash-dot-com>
>>
>>
>>> Original Poster: "Daniele Bortoluzzi" <dbortoluzzi-at-sogeda.it>
>> > I was wondering about power limiting issues, in effect a friend told
>that
>>a
>>> primary ballast, is it resistive or inductive, will reduce the voltage
>>input to the transformer.. is this right ?
>>
>>Yes, well, sort of. In fact the resistive ballast DOES limit the voltage
>>going into the NST or pig, therefore limiting the voltage output. An
>>inductive ballast, however, limits the CURRENT more than the voltage,
hence
>>achieving higher voltage in the primary. :)
>>
>>> So, what do you think is the good combination ? Variac and ballast ?
>>Variac
>>> only ? Variable ballast only ???
>>
>>It's a tough choice, we've all thought about that one. I personally have
>put
>>together my ballast with a combination of the two. I have yet to get my
>>'big bruiser' coil operating however, because of my brain injury.
>>
>>> Imagine I want to build a "Triac based" (I have a 400 Volt 20 Ampere
one)
>>watt
>>> absosption limiter rated
>>> for something like 1.5KVA maximum, am I going the right way to limit
>>current
>>> absorption from the transformer ?
>>> Is this triac suitable for coil use ???
>>> This cause I would like to have a "precise" limiting value... with a
nice
>>> tweedling knob there to play with power ;)
>>
>>That would be fun to do! regardless of the risk of limiting any power.
>>
>>
>
>
>