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Re: Ballast Transformers.
On Thu, 09 Mar 2000 13:48:59 -0700, Tesla List wrote:
> Original Poster: "Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net>
>
> Hi Mark,
>
> > Original Poster: "Mark Broker" <broker-at-uwplatt.edu>
> > A ballast is a small step-up transformer. But, the power-handling is
> >very low. I think on a standard 4' light ballast, the voltage is only
> >a couple kV.
> >The current is also quite low (a 4' flourescent bulb is rated ~50W).
> >I was told that a ballast also modifies the frequency, or rectifies it,
> >but I have seen slow-motion pictures that show the lights flickering
> >at about 60Hz.....
>
> A few corrections to the above post ;o))
>
> A ballast is NOT a transformer (although one can use an xformer as
> a ballast). A ballast has only ONE winding. In a fluorescent lamp a
> ballast does two things: First of all, it limits the maximum current
> that can flow (an "ac resistor") and second of all, it provides a
> starting "kick" for the lamp (they need HV to ionize the gas/mercury
> vapor inside the lamp). However, this HV "kick" is NOT due to
> "transformer" action, but rather that the inductor stores energy in
> the form J=0.5*L*I^2. In other words, the inductor tries to keep
> the same current flowing as you open the windings. It does this by
> raising the voltage (Ohm´s Law). Also, a ballast will do NOTHING
> to the frequency or towards rectifying the AC voltage. At a certain
> frequency, the ballast will appear to have zero ohms (not including
> the resistance, the copper wire has). This is called the resonance
> frequency, but it cannot change the applied frequency. It can´t
> rectify the AC, because it basically is nothing more than a coil of
> long wire.
>
>
> Coiler greets from Germany,
> Reinhard
If the ballast contains a ferromagnetic core, it is doubtful that the
inductive reactance will go to zero at resonance. Resonance of ferromagnetic
coils seems to be a misnomer. The only coils I could get to truly resonate
at 60 hz showing full ohms law conduction value were air coils of
commercially sold 14 gauge wire spools of 500 ft lengths.
By placing many of these in series I could contain enough resistance to
safely resonate them from wall voltage conditions. By then placing iron
cylinders in the cores I could derive a higher inductive reactance value,
but when this new reactive value was balanced with a new capacitive
reactance value, it did not then conduct the full ohms law value at its
designated new parameter of resonance, as was the case with an air core. To
give another example of the nonattainability
of ferromagnetic resonance take the typical 1.5 KVA power 440 volt
transformer. I measure 0.2 ohms on the primary, 2 ohms on the 440 secondary.
If I attempted to resonate the primary with the secondary open, by ohms law
conduction that would mean 120/0.2= 600 Amps, a situation that is easily
seen as impossible. Likewise if we attempted a series resonance of a typical
ferromagmetic fan motor, and not the more familiar tank or parallel resonant
circuit known as "power factor correction", we would find the motor burning
up because the wires could not hold the amperage, if it were to even
approach its ohms law
conduction values supposedly always attained at resonance. Ferromagnetic
coils cannot fully resonate because of the time lag of causitive voltage and
amperage produced and limited by the rotation of the inertial iron domains,
which then become less effective low loss reluctance paths at frequencies
past 400 hz. For ferromagnetic transformers that might function efficiently
these higher freq, and the superiority of a 4 phase system using a low
hysteresis loss transformer see 4 phase vs 3 phase/transformer without
hysteresis
at my messageboard under Searl machine HDN
Binary Resonant System
http://www.insidetheweb-dot-com/mbs.cgi/mb124201
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