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Re: NEON- Re: dimming HPF
tmjdorr wrote:
>
> Dave,
>
> >>National Cathode Corp. in New York dimmed HPF transformers regulary with
> Variac dimmers. Putting the correct size cap. in series [parallel???] across the
> primary of a NPF should make it a HPF. On the Tecnoservice transformers (a
> TecnoLux company) the Cap. is on the lid with the primary disconect . Change the
> lid, change the power factor. David Ablon<<<
>
> I stand corrected. I had not considered the variac method for dimming HPF
> transformers (per my reference to "switching" dimmers).
>
> As an aside, I thought most manufacturers did their PF correction by using an
> autotransformer type primary winding in order to use a smaller capacitor
> (physically, value-wise, and $-wise. Your statement implies that they just drop
> a cap right across the line terminals. Is this impression accurate?
>
> Regards,
>
> Telford Dorr
Dirk is additing:
As we have here in Europe an average mains supply of 230 volt we never
have an autotransformer type primary winding build into our
neontransformers . Compared with your mains our correcting capacitors
are so small. I know that Millers book is describing it that way but
that only counts for your country. On the other hand when I look to
modern capacitors and how small (little?) they are I don't think that a
additional winding to the primary makes sense any longer. I think that
even for you low voltage mains supply a direct connection accross the
mains is the best solution. Look to the size of medern capacitors, an
old 10 muF capacitor is bigger then a modern 20 muF capacitor and cost
nearly the same. Even when we must correct our biggest standard model
the 8 kV 50 ma transformer we can install a capacitor of double the
needed value of the capacitor in the high top lid. For sure using these
stand alone transformers is the best way to correct phase shift by using
the high top lid. We call that individual cos phi correction. When we
must install two of these transformers for one sign and these
transformers are installed next to each other we correct one transformer
installing twice the capacity and the other one is inductive. Then the
line is complete corrected as tension and current are in phase.
Using the variac for dimming purposes of neontransformers install an
average value of the capacitor, to prevent that there will be a
situation created that the line always is capacitive. So never install
the nominal effective value of the capacitor if you know that most of
the time the installation is dimmed by a variac.
Best regards from dirk a. boonstra
References: