H
Hiking
- Jan 1, 1970
- 0
Hello,
I wrote back:
Something wrong with the 2nd sentence above. Ok, think I got it, what
you're saying is:
Second, the simplest ballast is just a series impedance. A resistor or
inductor if used at power line frequencies, inductor or capacitor if
used at frequencies above about 5 kHz.
Ok, this may make sense now... the ballast is inline in the circuit, and
thus if the current "attempts" to increase, then the back-EMF increases
as a result of the additional magnetic lines of force cutting the
winding's conductors, effectively neutralizing the "attempted increase"
in current (actually, there would indeed be a very slight increase in
current, which would immediately be countered by back-EMF, which lowers
current, which lowers back-EMF, and the cycle starts over, on and on,
many a times second). This about right?
If my above understanding is correct, then I do understand what you mean
by saying that the ballast is analogous to a current source.
And one could say that as the arc in the lamp causes heat to increase,
and resistance/impedance to drop as result of higher temperature, the
current would then start to increase, but as mentioned above, would be
immediately countered by the ballast. You say that there is no
interaction between the bulb and ballast, I suspect, because one
perpetually pushes against the other (as per previous sentence), this
can be seen this way from both sides (lamp/ballast), and since this
interaction between the bulb and the ballast is stable, and for all
intents and purposes never changes, there is no real purpose in talking
about this as an interaction.
I have not received a response, so would just like to make certain that
I have a correct understanding of how the ballast works in a lighting
circuit. Does the above make sense? Thanks.
...
The current control function of the ballast can be quite simple.
First, the ballast could be a current source. In that case there is no
real "interaction" with the lamp, as the ballast will always provide a
fixed current. I know this may be hard to conceive, but we use voltage
sources all the time and these are designed to provide a very wide
range of currents while keeping the voltage constant, or just about
constant. Without understanding how a current source works internally,
you should still be able to conceive of such an object as an analog of
the common voltage source.
Second, the simplest ballast is just a series impedance. A resistor or
inductor if used at power line frequencies or resistor, inductor or
capacitor of used at frequencies above about 5 kHz.
I wrote back:
Something wrong with the 2nd sentence above. Ok, think I got it, what
you're saying is:
Second, the simplest ballast is just a series impedance. A resistor or
inductor if used at power line frequencies, inductor or capacitor if
used at frequencies above about 5 kHz.
Ok, this may make sense now... the ballast is inline in the circuit, and
thus if the current "attempts" to increase, then the back-EMF increases
as a result of the additional magnetic lines of force cutting the
winding's conductors, effectively neutralizing the "attempted increase"
in current (actually, there would indeed be a very slight increase in
current, which would immediately be countered by back-EMF, which lowers
current, which lowers back-EMF, and the cycle starts over, on and on,
many a times second). This about right?
If my above understanding is correct, then I do understand what you mean
by saying that the ballast is analogous to a current source.
And one could say that as the arc in the lamp causes heat to increase,
and resistance/impedance to drop as result of higher temperature, the
current would then start to increase, but as mentioned above, would be
immediately countered by the ballast. You say that there is no
interaction between the bulb and ballast, I suspect, because one
perpetually pushes against the other (as per previous sentence), this
can be seen this way from both sides (lamp/ballast), and since this
interaction between the bulb and the ballast is stable, and for all
intents and purposes never changes, there is no real purpose in talking
about this as an interaction.
I have not received a response, so would just like to make certain that
I have a correct understanding of how the ballast works in a lighting
circuit. Does the above make sense? Thanks.