Re: Cold Cathode Transformer

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Vladimiro Mazzilli <mazvla@xxxxxx>

All the transformers that is used to supply discharge lamps are current
limited because an arc also in low pressure lamps has a negative
resistance characteristic at current increase the lamp voltage decrease.
The differences between cold and hot cathode is in the voltage of
luninous column (depending of gas mixture) and the cathode voltage drop,
in cold cathode are very high, in hot cathode are very low infact for
220V are ballasted directly from the mains or with a shunted resonant
small transformer Slimline PS. The bombarder xformers have a good
coupling usually can give more than 1A at 15kV. They cause the cold
catode to reach a red color during tube forming while the vacuum pump
extract more of tube impurity. The ballasting is on the primary winding
and is a variable inductor, a long solenoid  with the internal iron free
to move. When iron is all inside, the inductance is maximum and it
decrease pulling it out.

Cheers

Vladi

Tesla list ha scritto:

> Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
>
> Just use a variac ahead of the xmfr with a 20 amp breaker.  Set the
> sparkgap close and bring the power up while monitoring the
> current.  Some of them, as bombarders were not current limited, but
> it sounds as if yours is current limited.
>
> Dr. Resonance
>
> >I have the good fortune of recently purchasing a
> >15000V, 120mA "Cold Cathode" transformer made my
> >Transco.
> >
> >The gentleman that I bought it from told me that Cold
> >Cathode transformes are not current limited.  I've
> >searched the list archives and have found a message
> >that states they *are* current limited.
> >
> >So, here's the question, how can I tell if it is
> >current limited without damaging it?  Is there any
> >danger in drawing an arc and monitoring the current?
> >
> >Thanks,
> >
> >Curt.